Horm Metab Res 2019; 51(07): 419-436
DOI: 10.1055/a-0661-0341
Review
© Georg Thieme Verlag KG Stuttgart · New York

The 3PAs: An Update on the Association of Pheochromocytomas, Paragangliomas, and Pituitary Tumors

Paraskevi Xekouki
1  Department of Endocrinology, King’s College Hospital, London, UK
2  Division of Diabetes & Nutritional Sciences, King’s College London, London, UK
,
Ana Brennand
2  Division of Diabetes & Nutritional Sciences, King’s College London, London, UK
,
Ben Whitelaw
1  Department of Endocrinology, King’s College Hospital, London, UK
,
Karel Pacak
3  Section on Medical Neuroendocrinology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, USA
,
Constantine A. Stratakis
4  Section on Endocrinology and Genetics, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, MD, USA
› Author Affiliations
Further Information

Correspondence

Constantine A. Stratakis
CRC – Rm 1-3330
East Laboratories
Building 10-CRC
10 Center Drive
SEGEN, NICHD, NIH
Bethesda
MD 20892
USA   

Publication History

received13 March 2018

accepted 09 July 2018

Publication Date:
01 October 2018 (eFirst)

 

Abstract

Pituitary adenomas (PA) and pheochromocytomas/paragangliomas (PHEO/PGL) are rare tumors. Although they may co-exist by coincidence, there is mounting evidence that genes predisposing in PHEO/PGL development, may play a role in pituitary tumorigenesis. In 2012, we described a GH-secreting PA caused by an SDHD mutation in a patient with familial PGLs and found loss of heterozygosity at the SDHD locus in the pituitary tumor, along with increased hypoxia-inducible factor 1α (HIF-1α) levels. Additional patients with PAs and SDHx defects have since been reported. Overall, prevalence of SDHx mutations in PA is very rare (0.3–1.8% in unselected cases) but we and others have identified several cases of PAs with PHEOs/PGLs, like our original report, a condition which we termed the 3 P association (3PAs). Interestingly, when 3PAs is found in the sporadic setting, no SDHx defects were identified, whereas in familial PGLs, SDHx mutations were identified in 62.5–75% of the reported cases. Hence, pituitary surveillance is recommended among patients with SDHx defects. It is possible that the SDHx germline mutation-negative 3PAs cases may be due to another gene, epigenetic changes, mutations in modifier genes, mosaicism, somatic mutations, pituitary hyperplasia due to ectopic hypothalamic hormone secretion or a coincidence. PA in 3PAs are mainly macroadenomas, more aggressive, more resistant to somatostatin analogues, and often require surgery. Using the Sdhb +/− mouse model, we showed that hyperplasia may be the first abnormality in tumorigenesis as initial response to pseudohypoxia. We also propose surveillance and follow-up approach of patients presenting with this association.


#

Introduction

Pheochromocytomas and paragangliomas (PHEOs/PGLs) are rare neuroendocrine tumors that produce catecholamines and arise from three structures derived from the neural crest: the adrenal medulla (PHEOs) and the sympathetic and parasympathetic paraganglia (PGLs) [1]. Most PHEOs are sporadic, unicentric and unilateral, but up to half (or even more, depending on the age of presentation) may be familial, multicentric and bilateral [2]. In recent years, substantial progress has been accomplished in the field of genetics and pathogenesis of PHEO/PGL and we know now that there are more than 20 susceptibility genes [3] including the genes encoding the four succinate dehydrogenase complex (SDH) subunits (SDHA, -B, -C, -D or SDHx collectively) [4] [5] [6] [7]. Mutations/functional variants of SDHx have also been implicated in Carney–Stratakis dyad or syndrome and, rarely, in Carney triad [8], renal cancer [9] [10] [11] [12], pancreatic neuroendocrine tumors [13] and Cowden-like syndrome [14].


#

Frequency of SDHx mutations in pituitary adenomas and the new syndromic association (3PAs)

In 2012, we described a family with multiple PGLs and PHEOs caused by a germline SDHD mutation; the index case also had an aggressive GH-secreting pituitary adenoma (PA) [15]. We found loss of heterozygosity (LOH) at the SDHD locus in the pituitary tumor, along with increased hypoxia-inducible factor 1α (HIF-1α) levels. These findings indicated that the SDH defect was most likely causatively linked to the development of the pituitary tumor and that pseudohypoxia pathways were activated, as shown in PHEOs/PGLs that bear SDHx mutations [15] [16].

However, what was also significant, was that the case of this patient was similar to several other cases previously reported since 1952; in most of these reports, the co-existence of PHEOs/PGLs and PAs was thought to represent a mere coincidence [17]. Following our 2012 publication, additional cases of PAs among patients with SDHx defects were described; today, it is widely accepted that the association of PAs with PHEOs and/or PGLs, or the 3 P association (3PAS) represents a new inherited form of a predisposition to multiple endocrine tumors caused by SDHx defects [18] [19] [20] [21] [22] [23] [24] [25].

Indeed, to investigate the frequency of germline SDHx mutations in PAs we sequenced 168 patients with sporadic and familial PAs. Overall, SDHx mutations were rare: 1.8% of the studied cases [26], in accordance with other reports [18] [25] [27]. However, among the patients included in the cohort, there were 7 that had presented with medical or family history of PHEOs/PGLs [26]; these patients had SDHx sequence pathogenic defects. Whenever family samples were available, we were able to show that SDHx defects were associated with either PHEOs/PGLs or PAs or both. On the other hand, in the few patients where PHEOs/PGLs and PAs were found in the sporadic setting (there was no family history or prior medical history of other SDHx-related defects), no SDHx mutations were identified. The difference was highly significant with more than 75% of patients with 3PAs and positive family history bearing SDHx mutations [26]. The overall prevalence of 3PAs with SDHx mutations irrespective of family history was 42.8% (3 out of 7 detected cases). Similar results were obtained in a different cohort of patients with PAs. Denes et al. studied 39 patients with sporadic or familial PHEO/PGL and/or PAs. Eight patients with SDHx mutations or variants within an international cohort of 19 patients with both tumors, were identified, which accounted for 42.1% of the affected subjects. Five out of the 8 cases (62.5%) were found within families with familial PHEOs/PGLs [22]. There was also a single patient with an SDHAF2 variant located in the 5′-UTR.

Interestingly, in the cohort studied by Denes et al., there were also 4 cases who presented with PHEO/PGLs and PAs but were found to harbor VHL or MEN1 gene mutations [22]. These 2 cases of PA and PHEO/PGL co-existence in patients with VHL mutations are the only ones reported in the literature, so far. Considering the frequency with which patients with VHL undergo regular surveillance imaging of the brain, the low frequency may indicate that the association of VHL and PA probably does not represent a true (genetically linked) predisposition. On the other hand in the 2 cases with MEN1 mutations, LOH was identified in the available PHEO tissue, indicating that PHEOs and/or PGLs can be part of the MEN 1 syndrome (as the Men1 knock-out animal model also suggests); thus, genetic testing for menin mutations should be considered in patients with PHEO/PGL if there are other suggestive signs of MEN 1. MEN 4 (the CDKN1B gene, coding for p27) may also be screened for in patients with an MEN 1-like phenotype, PAs, and PHEOs/PGLs that do not have menin or SDHx defects [22] [28] [29] [30] [31] [32].

We reviewed all the reported cases so far of the combination of PAs and PHEOs/PGLs since 1952 (eighty-two in total), including a recent report published while our manuscript was under review [33]. Literature search was done using PubMed, Scopus, and Google Scholar as search engines and “pituitary adenoma”, “3PAs”, “pheochromocytoma”, “paraganglioma” and combinations as search terms. Thirty-one (37.80%) of these cases harbored mutations in predisposing PHEOs/PGLs or PA genes. Twenty-two patients (26.82%) of all 3PAs cases had a personal or family history suggestive of a hereditary endocrine syndrome, whereas thirty-seven of all cases (45.1%) were isolated; for the rest 28% no information regarding family history was available ([Table 1], [2]). Among the 82 3PAs cases described so far, 17% had both identified genetic mutations and family history. This co-existence was much higher (48.38%) if we consider only the cases with a genetic defect. Regarding the frequency of the identified genetic defects it is obvious that the majority of cases carry SDHx defects (19 out of 31 cases, 61.3%), with MEN1 and MAX being the second and third most frequently related genes. Of course, due to the retrospective nature of this review and the lack of genetic screening in the majority of 3PAs cases, generalizations regarding the overall frequency of the implicated genes should be avoided.

Table 1 Patients with pituitary adenoma and pheochromocytoma/paraganglioma syndrome (3PAs) with identified germline genetic defects.

Pituitary

Pheo/PGL

Patient Nr

Sex

Type

Size

Treatment

Age

Type

Treatment

Age

Family history

Mutation

LOH/ICH in PA

Reference

1

F

PRL

NK

NK

27

Pheo

NK

NK

No

SDHA c.91 C>T p.Arg31Ter, VHL c.589 G>A p.Asp197Asn

Not performed

Dénes et al. (2015) [22]

2

F

PRL

Macro

NK

49

PGLs

NK

49

NK

SDHA p.Arg31* c.91 C>T

SDHA/SDHB negative staining

Niemeijer et al. (2015) [13]

3

M

GH

Macro

SSA

84

PGL

No

84

No

SDHAF2 c.-52T>C

Not performed

Dénes et al. (2015) [22]

4

M

PRL

Macro

DA, surgery

33

PGL

Surgery

33

Mother: PRL, brother: PGL

SDHB c.298 T>C p.Ser100Pro

LOH at SDBH locus, intracytoplasmic vacuoles

Dénes et al. (2015) [22]

5

F

NFPA

Macro

Surgery x3, RT

53

PGL

RT

28

Sister: glioma

SDHB c.587 G>A p.Cys196Tyr

LOH at SDBH locus/ SDHB staining: diffuse /intracytoplasmic vacuoles

Dénes et al. (2015) [22]

6

F

PRL

Macro

DA

38

PGLs carotid and mediastinal

Carotid: surgery, mediastinal: inoperable

35

Brother PGLs

SDHB mutation, (actual genetic defect not available)

Not performed

Gorospe et al. (2017) [76]

7

F

PRL

Macro

DA, RT

60

PGL

RT

60

NK

SDHB c.423 + 1 G>A

Not performed

Dénes et al. (2015) [22]

8

F

NFPA

Micro

No

50

Pheo

Surgery

50

NK

SDHB c.770dupT p.Asn258GlufsTer17

Not performed

Dénes et al. (2015) [22]

9

M

GH

NK

SSA

72

PGL

No

70

Brother & niece: PA, sister: bilateral HNPGL

SDHB c.689 G>A p.Arg230His

Not performed

Xekouki et al. (2015) [26]

10

F

PRL

Micro

NK

50

PGL

NK

47

Brother: HNPGL, grandmother: GIST

SDHB c.642 + 1 G>A, splice site alteration

Not performed

Xekouki et al. (2015) [26]

11

F

PRL

Micro

DA

33

PGL

Surgery

43

Brain tumor

SDHB c.18 C>A p.Ala6Alaa 3 PTEN polymorphisms

Not performed

Efstathiadou et al. (2014) [77]

12

F

PRL

Macro

DA

38

PGL

SSA

NK

Brother index case: PGL. Mother and sister positive for region of ex. 1 of SDHB

deletion affecting ex. 1 of SDHB

Not performed

Guerrero Pérez et al. (2016) [21]

13

M

PRL

Macro

DA

53

PGL

Surgery

38

Cousin: PA, brother: PGL

SDHC c.380 A>G p.His127Arg

Not performed

Dénes et al. (2015) [22]

14

F

PRL

Macro

NK

60

PGL

NK

60

No

SDHC c256-257insTTTpPhe85dup

Not performed

López-Jiménez et al. (2008) [78]

15

F

PRL

Macro

Surgery, DA

23

PGL

Surgery

32

Sister, aunt and grandmother: PA; sister: bilateral HNPGL

SDHD c.242 C>T, p.Pro81Leu

Not performed

Xekouki et al. (2015) [26]

16

M

PRL

Macro

DA, surgery

60

PGL, Pheo

Surgery (Pheo)

62

NK

SDHD c.274 G>T pAsp92Tyr

LOH at SDHD locus/SDHB positive ICH, SDHA IHC positive

Papathomas et al. (2014) [25]

17

F

GH

Macro

Surgery, SSA

56

PGL

NK

56

Father and 2 sisters: HNPGL; sister: GIST

SDHD c.274 G>T p.Asp92Tyr

LOH at SDHD locus/SDHB positive ICH, SDHA IHC positive

Papathomas et al. (2014) [25]

18

F

PRL

Macro

DA, surgery

33

PGL

Surgery x2

39

Aunt, uncle, brother: HNPGL

SDHD c.242 C>T p.Pro81Leu

Not performed

Varsavsky et al. (2013) [79]

19

M

GH

Macro

SSA, surgery

37

PGL, Pheo

Surgery

37

Sister and paternal uncle neck PGLs HNPGL

SDHD c.298_301del, premature stop at codon 133 AIP & CDKN1B polymorphism

PA: LOH at SDHD locus, reduced SDHD protein/ patchy SDHB staining

Xekouki et al. (2012) [15] [17]

20

M

GH/PRL

Macro

Surgery, RT, DA

27

Pheo

Surgery

31

No

MEN1 c.1452delG p.Thr557Ter

Menin staining of the Pheo: no menin positive cells

Dénes et al. (2015) [22]

21

F

NFPA

Macro

Surveillance

45

PGL

NK

45

No

MEN1 c.196_200dupAG-CCC frameshift (pathogenic), polymorphism C423T no amino acid change

Not performed in Pheo

Jeong et al. (2014) [80]

22

M

PRL

NK

NK

41

Pheo

Surgery

48

NK

MEN1 K119X, RET WT

Not performed in Pheo

Langer et al. (2002) [81]

23

NK

NK

NK

NK

NK

Pheo

NK

NK

Hyperparathyroidism and pancreatic islet cell tumor

MEN1 c.320del2

Not performed in Pheo

Dackiw et al. (1999) [32]

24

NK

NK

NK

NK

NK

Pheo

NK

NK

Pancreatic islet cell tumor and rectal leiomyoma

MEN1 1325insA

Not performed in Pheo

Dackiw et al. (1999) [32]

25

M

PRL

NK

NK

29

Pheo

NK

32

MEN1

Not performed, other family members MEN1 mutation

HPTH at age 21 years

Carty et al. (1998) [82]

26

M

GH

Macro

Surgery

62

Pheo

Surgery

62

No

RET p.Cys618Ser

Not performed in PA

Heinlen et al. (2011) [83]

27

M

ACTH

Micro

Surgery x2

48

Pheo

Surgery

66

Son: HPTH

RET c.1900T>C, p.Cys634Arg. Negative for MEN1 mutations

Not performed in Pheo

Naziat et al. (2013) [84]

28

F

PRL

Macro

DA

49

Pheo

Bilateral adrenalectomy

49

No

MAX c.296 G>T, Neg for MEN1, VHL, SDHB, SDHC, SDHD, SDHAF2, or TMEM127 genes

Not performed

Roszko et al. (2017) [34]

29

M

PRL

Micro

DA

49

Pheo

Surgery

32

No

Germinal heterozygous deletion of exon 3 of MAX (detected by MLPA). Neg for RET, VHL, SDHx, CDKN1B, AIP, MEN1

Not performed

Daly et al., (2018) [33]

30

F

GH

Macro

SSA, DA, Pegvisomant, RT

26

Bilateral Pheos

Bilateral adrenalectomy

35

No

Germinal heterozygous deletion of exons 1–3 and intron 3 of MAX. Neg for RET, VHL, SDHx, CDKN1B, AIP, MEN1

Not performed

Daly et al. (2018) [33]

31

M

GH

Macro

Surgery, RT

16

Bilateral Pheos

Bilateral adrenalectomy

22

No

Germinal heterozygous deletion of exon 3 of MAX (detected by MLPA). Neg for RET, VHL, SDHx, CDKN1B, AIP, MEN1

Not performed

Daly et al. (2018) [33]

M: Male; F: Female; NFPA: Non-functional pituitary adenoma; PRL: Prolactinoma; GH: Acromegaly; Macro: Macroadenoma; Micro: Microadenoma; DA: Dopamine agonist; RT: Radiotherapy; SSA: Somatostatin analogue; Pheo: Pheochromocytoma; PGL: Paraganglioma; HNPGL: Head and neck paraganglioma; PTC: Papillary thyroid cancer; GIST: Gastrointestinal stromal tumor; pNET: Pancreatic neuroendocrine tumor; MTC: Medullary thyroid carcinoma; HPTH: Hyperparathyoidism; NK: Not known; MEN1: Multiple endocrine neoplasia type 1; NF1: Neurofibromatosis type 1;

A: Single nucleotide polymorphism with a minor allele frequency of 0.2% and a genotype frequency of 0.5% (1000 Genomes Project Consortium, 2012) [85].

Table 2 Patients with pituitary adenoma and pheochromocytoma/paraganglioma without identified germline genetic defects.

Pituitary

Pheo/PGL

Patient Nr

Sex

Type

Size

Treatment

Age

Type

Treatment

Age

Family history

Mutation

Other Info (when reported)

Reference

1

M

PRL

Micro

Surgery

54

Pheo

Bilateral adrenalectomy

NK

No

Neg for RET, VHL, SDHB, SDHD mutations

Guerrero Pérez et al. (2016) [21]

2

F

GH

Micro

Surgery

56

Pheo

Bilateral adrenalectomy

NK

No

Neg for RET, VHL, MEN-1 mutations

Bilateral nodules on parathyroid glands, asymptomatic

Guerrero Pérez et al. (2016) [21]

3

M

PRL

Macro

Cabergoline

38

Pheo/PGL

α-Adrenergic blockade

NK

NK

Neg for MEN1

Catecholamine-mediated cardiac toxicity

Koshy et al. (2016) [86]

4

F

ACTH

Micro

Surgery

61

PGL

Surveillance

61

No

Negative for SDHA-D, MEN1, RET, AIP

Bilateral HNPGL

Xekouki et al. (2015) [26]

5

F

PRL

Macro

DA, surgery

35

Pheo

Surgery

55

No

Negative for SDHA-D, MEN1, RET, AIP

Bilateral Pheo

Xekouki et al. (2015) [26]

6

F

GH

Macro

Surgery

35

PGL

Surgery

58

No

Negative for SDHA-D, MEN1, RET, AIP

Bladder PGL

Xekouki et al. (2015) [26]

7

F

NFPA

Macro

Surgery

39

Pheo

Surgery

34

No

Negative for SDHA-D, MEN1, RET, AIP

Xekouki et al. (2015) [26]

8

F

GH

Macro

Surgery, RT, DA, SSA

56

Pheo

Surgery

66

No

Negative for SDHA-D, AF2, MEN1, RET, AIP, VHL, TMEM127, MAX, FH, CDKN1B

GIST, thyroid follicular adenoma

Boguszewski et al. (2012) [87], Dénes et al. (2015) [22]

9

M

NFPA

Macro

Surgery

53

PGL

Surgery

50

Father: PA

SDHA c.969 C>T p.Gly323Glya SDHB-D, AF2, MEN1, RET, AIP, VHL, TMEM127, MAX, FH, CDKN1B all normal

Abdominal PGL Wilms tumor, liposarcoma, renal oncocytoma; PA: no LOH at SDHA locus, intracytoplasmic vacuoles, SDHA and B staining preserved

Dénes et al. (2015) [22]

10

F

GH

Macro

Surgery, RT, SSA

39

Pheo

Surgery

20

No

Negative for SDHA-D, AF2, MEN1, RET, AIP, VHL, TMEM127, MAX, FH, CDKN1B

Dénes et al. (2015) [22]

11

F

NFPA

Macro

Surgery, RT

73

PGL

RT

73

No

Negative for SDHA-D, AF2, MEN1, RET, AIP, VHL, TMEM127, MAX, FH, CDKN1B

HNPGL

Dénes et al. (2015) [22]

12

M

GH

Macro

Infarcted

16

Pheo

NK

16

No

Negative for SDHA-D, AF2, MEN1, RET, AIP, VHL, TMEM127, MAX, FH, CDKN1B

Dénes et al. (2015) [22]

13

M

PRL

Macro

Surgery

40 s

PGL

NK

52

No

Negative for SDHA-D, AF2, MEN1, RET, AIP, VHL, TMEM127, MAX, FH, CDKN1B

HNPGL

Dénes et al. (2015) [22]

14

F

PRL

NK

NK

27

Pheo

NK

41

No

Negative for SDHA-D, AF2, MEN1, RET, AIP, VHL, TMEM127, MAX, FH, CDKN1B

Dénes et al. (2015) [22]

15

M

NK

NK

NK

NK

Pheo/PGL

NK

NK

No

Negative for SDHA-D, AF2, MEN1, RET, AIP, VHL, TMEM127, MAX, FH, CDKN1B

Dénes et al. (2015) [22]

16

F

PRL

Micro

DA

40

Pheo

Surgery

38

No

Negative for SDHA-D, AF2, MEN1, RET, AIP, VHL, TMEM127, MAX, FH, CDKN1B

Dénes et al. (2015) [22]

17

M

PRL

Micro

DA

56

Pheo

Surgery

56

No

Negative for SDHA-D, AF2, MEN1, RET, AIP, VHL, TMEM127, MAX, FH, CDKN1B

Dénes et al. (2015) [22]

18

F

PRL

Macro

DA

61

Pheo

Surgery

61

No

Negative for SDHA-D, AF2, MEN1, RET, AIP, VHL, TMEM127, MAX, FH, CDKN1B

Dénes et al. (2015) [22]

19

F

PRL

Macro

NK

60

PGL

RT

60

No

Negative for SDHB

Parghane et al. (2014) [88]

20

F

NFPA

Macro

No

52

Pheo

Surgery

52

No

Negative for SDHA-D, AF2, RET, MAX, TMEM127, VHL

GHRH secreting Pheo

Mumby et al. (2014) [89]

21

M

GH

Macro

Surgery

29

Pheo

Surgery

29

No

Not performed

Bilateral Pheo lipoma, metastatic PTC

Sisson et al. (2012) [90]

22

NK

GH

NK

NK

NK

Pheo

NK

NK

MEN1

Not performed

Bilateral Pheo HPTH, pNET Clinical features NF1

Gatta-Cherifi et al. (2012) [91]

23

M

GH

Macro

Surgery

45

PGL, Pheo

Surgery × 3

54

Father HNPGL, Sister: adrenal abnormality

Not performed

Abdominal, HN, cardiac PGLs

Zhang et al. (2011) [92]

24

M

NFPA

Micro

No

64

Pheo

Surgery

64

No

Not performed

High cortisol (cured post-adrenalectomy)

Yaylali et al. (2008) [93]

25

M

NFPA

Macro

Surgery

59

Pheo

Surgery

59

No

Not performed

Breckenridge et al. (2003) [94]

26

M

NFPA

Macro

Surgery

56

Pheo

No

56

No

Not performed

Dünser et al. (2002) [95]

27

F

GH

Macro

Surgery

57

Pheo

Surgery

57

No

Not performed

Sleilati et al. (2002) [96]

28

M

NK

Micro

No

43

Pheo

Surgery

43

No

Negative for RET

Lipoma, pectus excavatum, pleomorphic parotid adenoma.
GH levels responded to OGTT post adrenalectomy

Baughan et al. (2001) [97]

29

F

NK

Micro

No

44

Pheo

Surgery

44

No

Not performed

Cushing's (cured post-adrenalectomy)

Khalil et al. (1999) [98]

30

M

GH

Macro

Surgery

41

Pheo, PGLs

Surgery

20

NK

Negative for RET

Teh et al. (1996) [99]

31

M

PRL

Macro

Surgery

20

PGL

Surgery

20

NK

Not performed

HNPGL

Azzarelli et al. (1988) [100]

32

M

PRL

Macro

DA

26

Pheo

Surgery

26

Father: metastatic MTC and probably Pheo

Not performed

Bertrand et al. (1987) [101]

33

F

NFPA

NK

NK

70

PGL

NK

70

Daughter and granddaughter: PA, bilateral HNPGL

Not performed

HPTH, PTC, gastric leiomyoma, amyloidosis

Larraza-Hernandez et al. (1982) [102]

34

F

PRL

Micro

NK

35

Pheo

NK

35

NK

Not performed

Meyers (1982) [103]

35

M

NFPA

Macro

Surgery

66

PGL

Surgery

63

NK

Not performed

Blumenkopf & Boekelheide (1982) [104]

36

F

GH

NK

Surgery, RT

53

Pheo

Surgery

58

Brother: hypertension

Not performed

Anderson et al. (1981) [105]

37

F

GH

NK

RT

33

Pheo

None

45

No

Not performed

Multinodular goiter

Anderson et al. (1981) [105]

38

F

GH

Macro

NK

53

Pheo

NK

53

NK

Not performed

HPTH

Myers & Eversman (1981) [106]

39

F

PRL

NK

NK

23

Pheo

NK

23

NK

Not performed

HPTH, gastrinoma, adrenal adenoma

Alberts et al. (1980) [107]

40

F

NK

Macro

NK

22

Pheo

NK

22

Granddaughter: unilateral Pheo

Not performed

Islet cell tumor/ renal adenoma

Janson et al. (1978) [108]

41

F

GH

Macro

NK

15

Pheo

NK

15

NK

Not performed

HPTH

Manger & Glifford (1977) [109]

42

F

NFPA

NK

NK

49

Pheo

None

49

NK

Not performed

Papillary carcinoma of thyroid

Melicow (1977) [110]

43

M

GH

NK

NK

21

Pheo

NK

44

NK

Not performed

Kadowaki et al. (1976) [111]

44

F

GH

NK

NK

19

PGL

NK

19

NK

Not performed

PGL (HN, pelvis), HPTH

Farhi et al. (1976) [112]

45

F

GH

NK

NK

36

PGL

NK

36

NK

Not performed

HNPGL, HPTH, hyperplasia of antral and duodenal gastrin cells

Berg et al. (1976) [113]

46

F

NK

Micro

NK

43

Pheo

NK

43

NK

Not performed

MTC

Wolf et al. (1972) [114]

47

F

GH

NK

RT

36

Pheo

Surgery

36

NK

Not performed

toxic nodular, goiter, endometriosis, and diabetes, DM

Miller & Wynn (1971) [115]

48

M

ACTH

NK

NK

NK

Pheo

Surgery

41

VI generations with MEN

Not performed

MTC

Steiner et al. (1968) [116]

49

M

GH

Macro

RT

23

Pheo

None

41

NK

Not performed

Kahn & Mullon (1964) [117]

50

M

GH

NK

NK

NK

Pheo

NK

NK

NK

Not performed

German & Flanigan (1964) [118]

51

M

GH

NK

NK

44

Pheo

NK

NK

NK

Not performed

Iversen (1952) [119]

M: Male; F: Female; NFPA: Non-functional pituitary adenoma; PRL: Prolactinoma; GH: Acromegaly; Macro: Macroadenoma; Micro: Microadenoma; DA: Dopamine agonist; RT: Radiotherapy; SSA: Somatostatin analogue; Pheo: Pheochromocytoma; PGL: Paraganglioma; HNPGL: Head and neck paraganglioma; PTC: Papillary thyroid cancer; GIST: Gastrointestinal stromal tumor; pNET: Pancreatic neuroendocrine tumor; MTC: Medullary thyroid carcinoma; HPTH: Hyperparathyoidism; NK: Not known; MEN1: Multiple endocrine neoplasia type 1; NF1: Neurofibromatosis type 1; GOTT: Glucose oral tolerance test;

a Single nucleotide polymorphism with a frequency of 3.5% (Bayley et al. 2005) [120].

In a most recent publication Daly et al., reported 3 patients who presented with 3PAs and were found to have MAX exon/intragenic deletions using multiplex ligation-dependent probe amplification (MLPA), confirming a previous report of Roszko et al. [34]. The authors recommend that MAX MLPA should be considered in 3PAs and in PHEO cases in individuals screened negative with Sanger sequencing for the reported genetic causes including MAX mutations.

Despite the new identified genetic mutations/variants associated with 3PAs, for the majority of cases we do not know what other PHEOs/PGLs-causing genetic defects may be associated with a predisposition to PAs. At this point, what one screens for (beyond SDHx, menin, and possibly p27) remains unknown but it should be guided by detailed medical and family history, the latter extending to previous generations and even distant relatives, as these mutations often have weak penetrance. One should also avoid the effort to “fit” unusual cases into the known conditions: it is evident that the known classification of MEN syndromes does not always cover rare individual cases that present with significant overlap in their phenotype or, even, seemingly unrelated clinical signs that may represent new associations. Regarding the 51 cases of 3PΑs with no known genetic defect ([Table 2]) most of them are older and genetic testing was not available. Therefore, we cannot exclude the possibility that they harbor a genetic defect in any of the implicated genes; for some of them and based on the clinical presentation and family history the genetic defect is obvious. However, in the rest of the cases and particularly where genetic screening was negative, the co-existence of a PA and a PHEO or PGL may indeed represent an extremely rare coincidence due to mutations in co-segregating genetic defects or epigenetic changes; few cases may be explained by ectopic hormone secretion by a PHEO/PGL mimicking a functioning PA. Regarding the reported variations in sporadic PAs in [Table 3], most of them are variants of unknown significance and some of them are predicted to be damaging using the available prediction tools. However, one should perform functional studies to prove their deleterious effect.

Table 3 SDHx variants/mutations in pituitary adenomas.

Patient Nr

Gene

Sex

Age

Type

Size/Treatment

ICH/LOH

Other tumors/ conditions

Family history

Genetics tested/Prediction

Reference

1

SDHB

F

49

PRL

Micro/NK

SDHB positive

PHPT

Aunt: ACTH PA

c.5 C>T; p.A2V [Deleterious (SIFT)/benign (PolyPhen)]

de Sousa et al. (2017) [27]

2

SDHC

F

34

PRL

Micro/NK

SDHB positive

None

Brother: PRL PA

c.403 G>C; p.E110Q (Deleterious (SIFT)/possibly damaging (PolyPhen) )

de Sousa et al. (2017) [27]

3

SDHC

F

63

GH

NK

SDHB positive

Pituitary gangliocytoma, PHPT

No

p.E110Q [Deleterious (SIFT)/possibly damaging (PolyPhen)]

de Sousa et al. (2017) [27]

4

SDHA

M

62

NFPA

Macro/TSS

Loss of staining for both SDHA and SDHB

None

No

c.725_736del/c.989_990insTA (double hit)

Gill et al. (2014) [18]

5

SDHB

F

35

PRL

Macro/TSS

intracytoplasmic vacuoles

None

Mother: Prolactinoma, brother: PGL

c.298 T>C (damaging mutation)

Dénes et al. (2015) [22]

6

SDHA

M

30

NFPA

Macro/TSS

ICH negative for SDHA and SDHB

None

Mother carotid body paraganglioma

c.1873C>T p.His625Tyr

Dwight et al. (2013) [24]

7

SDHB

NK

15

NK

NK

NK

NK

NK

ex. 7 c.761insC p.254fsX255

Benn et al. (2006) [121]

8

SDHD

M

12

Cushing

Micro/TSS

Not studied

Thyroid

No

ex. 2 c.53 C>T, p. Ala18Val (very rare SNP (allele frequency <0.001) Benign (PSIC 0.004) (by PolyPhen) Deleterious (Score 0.01) (by SHIFT)

Xekouki et al. (2015) [26]

9

SDHB

F

31

PRL

Macro/TSS

LOH at SDHB locus in the PA/SDHB staining: loss of expression of SDHB

None

Grandmother’s first cousin PGL

del ex. 6 to 8

Dénes et al. (2015) [22]

10

SDHD

F

16

Cushing

Micro/TSS

Not studied

None

No

ex. 2 c.149 A>G/p.His50Arg (Probably damaging (PSIC 0.993) (Polyphen) Benign (Score 0.48) (SHIFT)

Xekouki et al. (2015) [26]

11

SDHB

F

14

Cushing

Micro/TSS

Not studied

None

No

ex. 5 c.487 T>C, p. Ser163Pro (reported as potentially pathogenic by Ni et al. 2012) [122]

Xekouki et al. (2015) [26]

12

SDHB

M

10

Cushing

Micro/TSS

Not studied

Brachydactyly/ dysmorphic features

No

ex. 5 c.487 T>C, p. Ser163Pro (reported as potentially pathogenic by Ni et al. 2012) [122]

Xekouki et al. (2015) [26]

M: Male; F: Female; NK: Not known; PRL: Prolactinoma; GH: Acromegaly; NFPA: Non-functional pituitary adenoma; Macro: Macroadenoma; Micro: Microadenoma; PA: Pituitary adenoma; PGL: Paraganglioma; PHPT: Primary hyperparathyroidism, TSS: Transphenoidal surgery.


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Phenotypic and pathological characteristics of PAs with SDHx mutations

We attempted to see whether PAs with SDHx mutations appear to have a different progression as previously described [21] [22] [25] [26]. Unfortunately, not all clinical data were available to make a safe distinction between the PAs as part of 3PAs with and without germline mutations. However, based on the available data from the reported cases we looked for any difference in phenotypic characteristics between PAs in the context of 3PAs with ([Table 1]) and without genetic mutations ([Table 2]) and the isolated PAs with SDHx mutations/variants ([Table 3]). The SDHx-related PAs in 3PAs were more common among familial cases, more frequently macroadenomas, they often led to multiple phenotypes within the same family (somatotropinomas, prolactinomas, and nonfunctioning adenomas) and required more than one modes of treatment ([Table 1] & Supl. Table 1S). Patients with isolated PAs and SDHx mutations/variants ([Table 3]) were significantly younger compared to the ones in cases with 3PAs regardless of the presence of a genetic mutation ([Table 1], [2]), and they all required surgery (regardless of the size of their tumors) but did not require multiple treatments (Supl. Table 4). A sub-analysis between the isolated PAs with SDHx mutations/variants and their counterparts in 3PAs, revealed that the latter were more frequently macroadenomas and required more than one treatment modality, which may suggest that the presence of PHEOs/PGLs may have contributed to the increased size and treatment resistance (Supl. Table 2S).

At this point, there does not appear to exist an apparent phenotype-genotype correlation, although very few families with 3PAS have other tumors associated with SDHx mutations such as gastrointestinal stromal tumors (GISTs) or renal cancer. The limited number of cases and the lack of prospective studies also do not allow for an accurate estimate of the expected age of presentation: based on the available cases ([Table 1], [3]) age at diagnosis ranged from as early as 15 years to as late as 72 years old. PHEOs or PGLs in these patients were bilateral and/or multiple, with a tendency to recur. The latter observation is one of the characteristics of SDHx-related PHEOs/PGLs [35].

Interestingly, in our first report, the growth hormone (GH) receptor (GHR) gene was found to be expressed in PHEO samples from our patient with the SDHD mutation, as well as in tumor samples from other patients harboring SDHB or SDHD mutations [15]. Based on this finding together with the clinical observation that there was a noticeable decrease (almost three-fold) of plasma and urinary metanephrines after pituitary transsphenoidal surgery (that was greater than the one noted following bilateral adrenalectomy for the patient’s PHEOs), we assumed that normalization of GH levels after TSS contributed significantly to such biochemical changes. This was the first and only study so far reporting the expression of GHR in PHEOs whereas there are reports of the differential expression of ghrelin and GH-releasing hormone (GHRH) receptors in various adrenal tumors, including PHEOs [36] [37] [38]. The role of GHR in SDHx-mutant tumors needs to be investigated further.

One interesting histological phenotype reported by Dénes et al. [22], in pituitary gland tissues from patients with SDHx mutations was the presence of intracytoplasmic vacuoles in their PAs. Although electron microscopy was not used to identify the exact nature of the vacuoles [39], there is a possibility that they represented autophagic bodies. The relationship between hypoxia-related pathways and autophagy activation is well established [40] [41] and autophagy has been shown to contribute to chemo- and radio-therapy resistance [42] [43]. We have described a similar morphological finding in the PA tissue of the original case with the SDHD mutation ([Fig. 1a]) [15].

Zoom Image
Fig. 1 a: H & E staining of the pituitary adenoma of the SDHD patient reported by Xekouki et al., 2012 [15] [17] showing cytoplasmic vacuoles (arrow) (× 40) b: Enlarged mitochondria with marked swelling and abnormal and/or missing internal cristae in pituitary cells of Sdhb +/− mice (electron microscopy 200 nm).

Loss of SDHB immunochemistry has been shown to be an excellent indicator of germline or somatic mutations in the SDHx genes [1] [44] [45]. In most of the SDHx-related PAs reported so far, completely absent or weak diffuse staining of SDHB was found (in those cases that this was performed) ([Table 1], [3]). Therefore, as in PHEOs/PGLs, SDHB staining may be used as an additional diagnostic tool to screen for SDHx mutations. Furthermore, as shown by Richter et al. [46], profiling of Krebs cycle metabolites, such as ratios of succinate:fumarate with the use of mass spectrometry, is another useful method to identify patients for testing of SDHx mutations and to assess functionality associated with SDHx variants of uncertain significance in PGLs. Although this method has not been used in any of the 3PAs cases it would be interesting to see whether it could predict the presence of SDHx mutations or distinguish damaging mutations from nonfunctional polymorphisms in pituitary adenomas in the context of 3PAs as in PGLs.

Traditionally LOH has been used in oncology to confirm the causative association between a tumor and the loss of a tumor suppressor gene [47]. As shown in [Table 1], in some cases no LOH studies were performed; in few cases no LOH of the SDHx mutated locus was identified. Does this mean that the absence of consistent LOH in PAs indicates lack of association with the identified SDHx mutations? Although this is difficult to answer with certainty at this time, bilateral adrenal medullary hyperplasia associated with a germline SDHB mutation showed retention of heterozygosity [48], and PHEOs without loss of the normal SDHD allele have been shown in patients with pathogenic SDHD mutations [49]. Additionally, cases of “paradoxical” loss of the mutant SDHx allele have been shown [24] [50], pointing to the suggestion that the SDHx defects may not always lead to tumorigenesis in the classical tumor suppressor gene way. Finally, epigenetic alterations such as somatic SDHC promoter methylation and postzygotic somatic mosaicism could provide another explanation for those cases negative for germline mutations [51] [52].


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Molecular mechanisms of SDHx mutations in the development of a PA

To further understand the causal relationship between PA and SDHx mutations, we analyzed the pituitaries of adult Sdhb + /− mice. Although no gross pituitary tumors were detected, the pituitary of 12-month old Sdhb +/– mice was hypercellular, mainly due to the increased number of prolactin (PRL)-secreting cells and to a lesser extend GH-secreting cells. There were also blood-filled lakes, abnormal mitochondria ([Fig. 1b]), nuclear inclusions of unknown nature, and abnormal and poorly defined heterochromatin forming a ring-shaped pattern rather than being centrally located as in pituitaries of the normal control animals [26]. Pituitary hyperplasia likely preceding the formation of adenomas, was found in 3- and 12-month-old Aip-deficient male mice [53] as well as in those lacking p19 (arf) or p27(kip–1), and those overexpressing the beta-catenin or the pituitary tumor-transforming gene (CTNNB1 and PTTG, respectively) [54] [55] [56] [57]. In humans, pituitary hyperplasia has been reported in patients with germline mutations in the PRKAR1A or AIP tumor suppressor genes, and in those with gigantism and chromosome Xq26 duplications [58] [59] [60].

Like in other SDHx-deficient PHEOs/PGLs [61], there is evidence that hypoxic signalling is activated in SDHx-mutated pituitary tumors [15]. This finding was supported by the HIF-1α strong cytoplasmic (and occasionally nuclear) expression in the pituitaries of Sdhb +/– mice [26]. Other evidence of hypoxia-activated pathway in these mice was the enlarged mitochondria with destructed cristae found in the Sdhb +/– animals [26] [62]. Similar mitochondrial findings have been reported in tumor samples from patients with Carney triad, as well as in paragangliomas from patients with SDHC and SDHD mutations [56]. Fragmented and defective mitochondria have been found in many different cancers and alterations in mitochondrial dynamics are associated with tumor progression or resistance to therapy [63]. The altered chromatin pattern that we also observed in Sdhb +/– mice, like the one observed in mice overexpressing PTTG and in hypoxic cells [55] [64] is another indication that chronic activation of pseudohypoxia in SDHx-deficient pituitary cells can drive genetic instability and eventually lead to tumor formation.

Although electron microscopy failed to identify the actual nature of the nuclear inclusions seen in Sdhb +/– pituitary cells with light microscopy, it has revealed that these appeared to be fused to the nucleus rather than being intranuclear. These inclusions resembled the vacuoles described by Denes et al., in SDHx-deficient pituitary tumors and may represent late autophagic vacuoles previously filled with digested abnormal mitochondria. Thus, we may speculate that PA formation from SDHx mutations may follow a long process, whereby hyperplasia is the initial response to a prolonged stimulation due to activation of pseudo-hypoxia signals ([Fig. 2]).

Zoom Image
Fig. 2 Proposed mechanism of tumor development in SDHx-deficient pituitary adenomas; SDHx mutations may initially lead to hyperplasia, as it was shown in Sdhb +/− mice, which eventually either at the presence of another mutation or epigenetic events it will lead to pituitary tumor development (H & E staining of the original case reported in 2012).

#

Recommendations for genetic screening and follow-up of patients with 3PAs

Although cases of 3PAs have been reported since 1952, it was only in 2012 when we showed that SDHx mutations may be involved in pituitary tumorigenesis [15]. So far there are 28 cases of confirmed SDHx mutation-related pituitary adenomas (with the variants of unknown significance excluded). Currently, we recommend that a detailed baseline medical and family history is taken from all these patients along with careful physical examination to detect signs of other tumors associated with SDHx defects (for examplle, GISTs) ([Fig. 3]). Hormonal testing should be obtained, once familial PHEOs and/or PGLs are recognized in the index case and their family members. Attention should be paid to any symptoms that would indicate GH or PRL hypersecretion and visual disturbance, as most of the pituitary adenomas in the context of 3PAs are PRL- or GH- secreting macro-adenomas or NFPAs. If there are no suspicious symptoms or findings and biochemistry is normal then annual biochemical surveillance should include testing for PHEOs/PGLs, as per the most recent recommendations [65] [66]. If at any time, clinical findings or biochemistry indicate hormonal hypersecretion, a pituitary MRI should be performed.

Zoom Image
Fig. 3 Recommended clinical investigation and follow-up in patients with 3PAs.

Treatment of PAs due to SDHx mutations should not differ from the recommended treatment for sporadic tumors [67] [68] [69] [70] [71]. However, it is possible that more than one treatment modalities will be required, as these tumors are often more aggressive and tend to recur more frequently than their sporadic counterparts (although this impression may change as more cases are now identified by screening and are followed prospectively).

Special attention should be given to patients that may have MEN1, MEN2, or MEN4, as now we know that all three syndromes may be associated with both PAs and PHEOs/PGLs. Thus, plasma or urine metanephrine measurements may be needed prior to surgeries in patients with suggestive signs and symptoms of a PHEO or a PGL. Finally, in case of a family history of a PHEO/PGL due to MAX mutation, careful medical history and physical examination should be performed in all mutation carriers for the presence of other tumors related to MAX mutations such as PA and renal cancer as recently described [33] [72].

Genetic testing for SDHx mutations should be performed in any patient who presents with 3PAs particularly if there is family history of PHEOs/PGLs in other family members (the latter may not only include first-degree relatives). In the absence of a family history of PHEOs/or PGLs, screening for SDHx mutations in patients with apparently sporadic 3PAS may also be performed, as these genetic defects are known to have low penetrance in affected families. Alternatively, and/or if genetic screening is not readily available, SDHB staining and succinate:fumarate ratio maybe another way to look for SDHx defects. The presence of intracytoplasmic vacuoles is another pathology finding strongly suggestive of SDHx gene defect. If screening for SDHx mutations is negative or pathology and biochemistry are not suggestive of SDHx defects, then screening for menin or RET mutations should be based on the presence of clinical features and/or tumors that would indicate the presence of the MEN1 or MEN2 syndromes. Screening for MEN4 is not considered routine at this point, as is the case for other genes known to predispose to PA development [73]. Finally, screening for MAX mutations should be considered if SDHx and menin are screened negative.


#

Final remarks

In the era of next generation, sequencing and new molecular techniques hundreds of new genes responsible for tumors have been discovered [74]. The opposite is also true: many new associations are found for mutations of the same gene(s). Indeed, today is the era of physician-researchers working like crime scene investigation (CSI) agents, gathering data carefully, connecting seemingly unrelated facts, and discovering new phenotypes for known gene defects [75]. The SDHx genes are very well suited for the investigation of new associations, as they are expressed in all cells, have an essential role in mitochondrial function, and their defects have low, overall, penetrance.


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Conflict of Interest

The authors declare no relevant conflicts of interest. This work was supported by the NICHD intramural research program.

Supplementary Material


Correspondence

Constantine A. Stratakis
CRC – Rm 1-3330
East Laboratories
Building 10-CRC
10 Center Drive
SEGEN, NICHD, NIH
Bethesda
MD 20892
USA   


Zoom Image
Fig. 1 a: H & E staining of the pituitary adenoma of the SDHD patient reported by Xekouki et al., 2012 [15] [17] showing cytoplasmic vacuoles (arrow) (× 40) b: Enlarged mitochondria with marked swelling and abnormal and/or missing internal cristae in pituitary cells of Sdhb +/− mice (electron microscopy 200 nm).
Zoom Image
Fig. 2 Proposed mechanism of tumor development in SDHx-deficient pituitary adenomas; SDHx mutations may initially lead to hyperplasia, as it was shown in Sdhb +/− mice, which eventually either at the presence of another mutation or epigenetic events it will lead to pituitary tumor development (H & E staining of the original case reported in 2012).
Zoom Image
Fig. 3 Recommended clinical investigation and follow-up in patients with 3PAs.