Keywords
mucocele - appendix - epithelial tumors
The mucocele of the appendix can be described as an obstructive dilatation of the
appendix by an intraluminal accumulation of mucus.[1]
[2]
[3] It can be caused by these four etiologies: retention cysts, mucosal hyperplasia,
cystadenomas, and cystadenocarcinomas. Clinically, it has a nonspecific presentation.
It is most commonly found incidentally during appendicectomy. The principles of surgery
for appendiceal mucocele include resection of the appendix, wide resection of mesoappendix
including all appendiceal lymph nodes, collection and cytologic examination of the
mucus, and inspection of the base of the appendix.[1]
[2]
[3] In case of positive margin at the base or positive periappendiceal lymph nodes,
right hemicolectomy or ileocecectomy is warranted.[3] Pseudomyxoma peritonei (PMP) is a dreaded complication of rupture of mucocele appendix
intraperitoneally. It is characterized by peritoneal tumor deposits, mucinous ascites,
omental caking, and ovarian involvement in females. The risk for developing PMP after
appendicectomy having epithelial tumor is around 9%.[1]
Case Presentation
A 60-year-old diabetic male patient presented with chief complains of pain in right
lower abdomen for the past 2 months which was dull in nature, not associated with
fever, vomiting, diarrhea, constipation, or any urinary complains. There was no associated
history of loss of appetite or weight loss and no history of hematemesis or melena.
The patient was taking treatment on and off but was not relieved. Per abdomen, examination
revealed a lump in the right iliac fossa region. All routine laboratory investigations
were unremarkable. Upper gastrointestinal (GI) endoscopy was unremarkable. Colonoscopy
showed edematous appendiceal lumen indenting into the cecum. No other abnormality
was detected. Ultrasonography of the abdomen revealed a dilated (15 mm), fluid-filled,
blind-ending, partially compressible, nonperistaltic bowel loop in the right iliac
fossa. The features were suggestive of appendiceal mucocele. Contrast-enhanced computed
tomography (CECT) of the abdomen revealed appendiceal lumen distended, filled with
fluid collection (iodine-related Hounsfield unit [IHU] value 9), measuring 2.8 cm
in diameter at its base with the appendiceal wall thickness of 3.5 mm ([Fig. 1]). There is abrupt narrowing seen at its junction with cecum. No obvious enhancing
nodular lesion/appendicolith was noted. No significant periappendiceal fat stranding
or fluid collection or adjacent enlarged lymph nodes were seen. Features were suggestive
of appendicular mucocele. The patient was taken up for exploratory laparotomy and
a distended turgid appendix, around 4 cm in diameter with dilated cecum was found.
Ileocecal resection was done followed by ileo-ascending colon side-to-side anastomosis
using staplers ([Figs. 2] and [3]). The postoperative stay was uneventful. Mucocele fluid cytology report showed abundant
macrophages along with inflammatory cells comprising lymphomononuclear cells and polymorphonuclear
cells in the background showing thick mucoid proteinaceous material. No atypical cells
were seen. Histopathological examination report revealed grossly enlarged and dilated
appendix. The base of the appendix showed narrow but patent lumen with mucosa bulging
into the cecal lumen. Focally lumen of the appendix showed thick gelatinous mucinous
substance. Section from appendix showed mucosa lined by flattened columnar mucinous
epithelium without significant dysplasia, thinned out wall with loss of lymphoid tissue
and submucosa. Underlying stroma showed mild to moderate chronic inflammatory infiltrate.
Sections taken from the appendix near the opening at ileocecal junction showed dissection
of acellular mucin in the wall up to muscularis propria. Features were suggestive
of low-grade appendiceal mucinous neoplasm (LAMN).
Fig. 1 Contrast-enhanced computed tomography of the abdomen showing dilated appendix.
Fig. 2 Resected specimen showing appendiceal opening with cecal and ileal opening.
Fig. 3 Resected specimen showing cut open appendix with mucous fluid content.
The histopathological examination report revealed an R0 resection. The patient was
followed up for 3 years postoperatively with CECT of the abdomen and a colonoscopy
yearly. There was no evidence of any recurrence in the follow-up. No specific GI symptoms
were seen.
Discussion
Appendiceal neoplasms are found in around 1% of appendicectomy specimens. Most of
them are found incidentally. Tumors of the appendix can be classified as carcinoid
or epithelial. Epithelial tumors of the appendix account for around 75% of the cases.
Carr et al classified the epithelial tumors broadly as mucinous or nonmucinous (intestinal
type). Their classification included adenomas (tubular, tubulovillous, villous), serrated
polyp, nonmucinous adenocarcinoma, mucinous neoplasm (LAMN, high-grade appendiceal
mucinous neoplasm, and mucinous adenocarcinoma), adenocarcinoma with signet ring cells
and signet ring carcinoma. Based on the degree of cytologic atypia and architectural
features, it was classified as infiltrative or pushing invasion.[1]
[2]
Goblet cell carcinoid, a rare tumor of the appendix, has now been recently reclassified
as a goblet cell tumor. It can be of mucinous or nonmucinous type. Goblet cell tumor
has both gland forming and neuroendocrine features.[1]
[4] Carcinoid tumors arise in argentaffin tissue (kulchitsky cells of the crypts of
lieberkuhn). They are most commonly seen in the appendix. It can occur in any part
of the appendix, but most commonly found in the distal one-third. Grossly on the cut
surface, it is seen as a yellow mass between the intact mucosa and peritoneum. Carcinoid
tumors of the appendix rarely metastasize.[1]
[4]
Treatment of mucocele appendix is appendicectomy primarily. Frozen section of the
base of appendix intraoperatively can help in distinguishing the mucocele from other
mucinous neoplasms. In case of simple mucocele and less than 2 cm in diameter, an
appendicectomy with removal of all fat and lymph nodes in mesoappendix is warranted.
However, in the case of positive margin at the base, dilated appendicular base more
than 2 cm or positive periappendiceal lymph nodes, right hemicolectomy, or ileocecectomy
is warranted.[3]
[5] There are various reports of association of mucocele of an appendix with colorectal
tumors and ovarian mucinous tumors. So, colonoscopy needs to be done in all patients
preoperatively as well as postoperatively in follow-up.[4]
[6]
[7]
Patients having low-grade epithelial neoplasms without any evidence of mucin or epithelial
cells beyond the appendix have a very low risk of PMP development. A colonoscopy should
be done to exclude any associated colonic epithelial lesions and patients kept in
surveillance postoperatively for at least 5 years. Surveillance may include clinical
review, annual abdominopelvic CT scan, and appendix-related tumor markers (CEA, CA
199, CA 125).[1]
Patients having a high-grade tumor, invasive adenocarcinoma or goblet cell tumor,
and/or those with an epithelial cell containing mucin outside the appendix have a
higher risk of nodal involvement and subsequent development of PMP. These patients
should be treated as patients with established PMP and considered for right hemicolectomy
with prophylactic regional (right parietal) peritonectomy, omentectomy, and intraperitoneal
chemotherapy. They should also be considered for bilateral salpingoophorectomy where
feasible.[1]
Treatment of PMP is cytoreductive therapy combined with hyperthermic intraperitoneal
chemotherapy. Cytoreductive therapy is achieved by multiple peritonectomy procedures
along with multiple visceral resections.[1]
[8]
[9]
[10]
Conclusion
Mucoceles of the appendix are most commonly found incidentally during an appendicectomy.
Frozen section of the base of appendix intraoperatively provides vital clues to distinguish
it from other mucinous neoplasms. Ileocecectomy can be done as a single-stage procedure
when anticipating the appendiceal base involvement during exploration or in case of
high suspicion in CECT of the abdomen for mucocele appendix. Laparoscopic appendicectomy
can also be performed for mucocele of the appendix, but the risk of rupture and further
complications of a PMP must be kept in mind.
