Keywords [
18 F] fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography scan
- maximum standardized uptake value ratio - tonsillar carcinoma
Introduction
The incidence of squamous cell tonsillar carcinoma is rising globally.[1 ] Positron emission tomography/computed tomography (PET/CT) using 2-[18 F] fluoro-2-deoxy-D-glucose
(18 F-FDG) is becoming increasingly important in the management of head and neck carcinomas,
which typically appear hypermetabolic.[2 ] However, inflammatory or infectious responses may look similar and thus can be mistaken
for malignancy. Various degrees of increased FDG uptake are observed in the palatine
tonsils due to its constant exposure to antigens, making an interpreting physician
prone to making a false-negative reading.[3 ] It is rare for a tonsillar lesion to be established as a primary carcinoma, especially
in a person already with two carcinomas.
Case Report
A 68-year-old male was referred to us for an 18 F-FDG PET/CT scan. He was diagnosed with colon and prostate carcinomas 1 year ago
based on tissue biopsies. He subsequently underwent hemicolectomy and prostatectomy.
No chemotherapy or radiotherapy was performed.
Two months prior, he noted pain and swelling in the right lateral neck, only partially
relieved by antibiotics. Ultrasound revealed either an abscess or a confluence of
infected lymph nodes. However, fine-needle aspiration biopsy of the right cervical
lymphadenopathy revealed atypical cells suspicious for malignancy. Serum carcinoembryonic
antigen and prostate-specific antigen levels were normal, but serum amylase was elevated
at 178.05 U/L (reference range: 30–110 U/L). A PET/CT scan was thus requested by his
attending oncologist for further evaluation.
Low-dose whole-body CT with slice thickness of 4 mm × 4 mm was performed for attenuation
correction. Emission images were then acquired with a Philips Gemini TF 64 PET/CT
scanner at 21 bed positions (90 s per bed position from head to mid-thighs and 20
s per bed position from mid-thighs to feet), 63 min after administration of a diagnostic
dose of 18 F-FDG. Fasting blood sugar was 75 mg/dL. Maximum weight-based standard uptake values
(SUVmax ) of the noted lesions were taken.
Multiple hypodense and/or necrotic lymph nodes were seen in the right cervical area
(Level II and III). The largest was at Level III, measuring 2.0 cm × 2.0 cm × 3.0
cm (AP × T × CC). Adjacent fat plains were not hazy. On PET, some of these nodes had
increased FDG uptake, with the largest node exhibiting uptake mostly in the periphery
[SUVmax 3.9; [Figure 1 ]. Incidentally, there was increased activity in the tonsils, the right appearing
more intense than the left [SUVmax 5.7 and 3.8, respectively; [Figure 2 ]. No significant findings were noted elsewhere. Tissue correlation was suggested
for the hypermetabolic right cervical lymph nodes. Tonsillar findings were said to
appear inflammatory or physiologic.{Figure 1}{Figure 2}
Figure 1 Axial (a) and coronal (b) positron emission tomography/computed tomography images
showing a fluoro-2-deoxy-D-glucose avid Level III lymph node in the right cervical
area (standard uptake value 3.9). Note increased uptake in the periphery of the node
relative to the center, consistent with possible central necrosis
Figure 2 Axial (a) and coronal (b) positron emission tomography/computed tomography images
of the tonsils showing increased fluoro-2-deoxy-D-glucose uptake, the right more than
the left (standard uptake value of 5.7 on the right tonsil and 3.8 on the left)
One month after the PET/CT scan, excision biopsy of the enlarged right cervical lymph
node revealed metastatic poorly differentiated carcinoma; no primary carcinoma was
favored, and immunohistochemistry was not done.
Contrast-enhanced magnetic resonance imaging (MRI) of the neck was done soon after
biopsy, with the right cervical area still showing some enlarged necrotic lymph nodes
at Level IIB. Slight asymmetry in the thickness of the palatine tonsils was noted
at the level of the uvula. The right palatine tonsil appeared slightly more prominent
without definite inhomogeneity and exhibited greater contrast enhancement than the
contralateral side [Figure 3 ]. This was interpreted as probably nonspecific; however, because of the enlarged
necrotic lymph nodes, an early neoplasm was not entirely ruled out. Tissue correlation
for the right tonsil was suggested.
Figure 3 Gadolinium contrast-enhanced magnetic resonance imaging of the neck (axial image)
showing the right tonsil with increased enhancement compared to the contralateral
side (arrow). This was determined to be a primary carcinoma on histopathology
Endoscopic biopsy of the right palatine tonsil was performed, with histopathology
consistent with squamous cell carcinoma. He later underwent tonsillectomy with neck
dissection. A follow-up neck CT post-surgery showed regression in the sizes of the
residual lymph nodes in the right cervical area.
Discussion
This report focuses on an elderly male patient with recently diagnosed carcinomas
of the colon and prostate, who was eventually assessed with tonsillar squamous cell
carcinoma. With such previous diagnoses and atypical cells on fine-needle biopsy,
the hypermetabolic enlarged right cervical lymph nodes could have been interpreted
as metastases from the known primaries. However, only about 1% of all head and neck
malignancies are due to metastases from a remote primary site, such as the gastrointestinal
and genitourinary tracts.[4 ] Thus, probability of a distant lymph node metastasis is low in this case.
Hypermetabolic tonsils, in the absence of known head and neck pathologies, are typically
interpreted as physiologic in nature. However, caution should be exercised for patients
with FDG-avid disease in the area, as exhibited by this case. On PET/CT, the right
palatine tonsil appeared more hypermetabolic than the left; on MRI, it was more prominent
and more enhancing. This may still correspond to a benign pathology such as tonsillitis,
which should respond to antimicrobial therapy. However, the clinical persistence of
the neck symptoms despite short-course antibiotics, along with enlarged necrotic FDG-avid
cervical lymph nodes, may have been enough grounds to suspect malignancy. An elevated
amylase level may have also supported such pathology, as this is normally noted in
organs such as the salivary glands, thyroid glands, and tonsils.[5 ]
A 2010 study highlighted the utility of SUVmax ratio in differentiating squamous cell tonsillar carcinoma from normal asymmetric
FDG uptake. SUVmax ratio is defined as higher tonsillar SUV divided by the lower SUV. Values of 1.48
or higher were consistent with malignancy.[3 ] In this patient, the SUVmax ratio was 1.5, coinciding with the said study finding. In retrospect, this may have
expedited the workup toward the eventual diagnosis. Furthermore, a PET/MRI would have
been more advantageous in this case due to the increased anatomic detail that MRI
can provide in head and neck malignancies.[6 ] However, PET/MRI is currently not yet available in the Philippines.
This case report shows how normal-looking tonsillar FDG uptake on PET/CT was eventually
determined to be a primary malignancy. On a background of enlarged cervical lymph
nodes and known carcinomas, uptake in the tonsils should never be quickly dismissed
as normal or inflammatory, especially with asymmetry in FDG uptake. Calculating the
SUVmax ratio is advised in similar future cases to rule out a probable tonsillar primary
malignancy.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form the patient(s) has/have given his/her/their consent for his/her/their
images and other clinical information to be reported in the journal. The patients
understand that their names and initials will not be published and due efforts will
be made to conceal their identity, but anonymity cannot be guaranteed.
