Primary appendiceal tumours are rare. They represent 0.2–0.5% of all intestinal malignancies;1 2
only 4–6% of primary appendiceal neoplasms are adenocarcinomas and the vast majority are neuro-endocrine tumours.1–5
There are two main histological classifications of appendiceal adenocarcinoma: mucinous and colonic. The presenting signs and symptoms of appendiceal mucinous adenocarcinoma are usually those of acute appendicitis or a palpable abdominal mass6
; however, unusual presentations include peritoneal carcinomatosis, haematuria due to bladder infiltration, direct invasion of the ascending colon noted on colonoscopy, hydronephrosis, retroperitoneal abscess, vaginal bleeding and cutaneous infiltration.7–15
These unusual presentations result from the propensity of appendiceal mucinous adenocarcinoma to perforate and to form fistulae to adjacent structures.
Adenocarcinoma of the appendix is the most frequently perforating tumour of the gastrointestinal tract.16
This is thought to be due to anatomical peculiarities of the appendix, which has an extremely thin subserosal and peritoneal coat and the thinnest muscle layers of the whole gastrointestinal tract. Perforation of an appendiceal mucinous adenocarcinoma can result in widespread seeding of tumour cells and mucin deposits throughout the peritoneum with the development of peritoneal carcinomatosis in some, but not all, cases.1 15
This slowly progressive tumour with associated mucinous ascites significantly worsens the prognosis of mucinous adenocarcinoma,15 17–19
although this is disputed by one large case series.6
Recent evidence suggests that even small localised peri-appendiceal tumour deposits impact negatively on long-term survival in the absence of peritoneal carcinomatosis.20
There was no evidence of perforation or of disseminated peritoneal mucin deposits or mucinous ascites in our patient either on CT or at laparoscopy. However, localised mucin deposition near to the appendiceal stump was seen at the second laparoscopy.
In addition to the risk of perforation, mucinous adenocarcinoma is thought to have a particular tendency for fistula formation.21
Many of the unusual presentations reported for primary appendiceal mucinous tumours are the result of fistula formation into adjacent viscera such as the urinary bladder, bowel and vagina as well as extra-peritoneally into the retro-peritoneal tissues or directly to the skin surface. The patient reported here developed an enterocutaneous fistula following incision and drainage of an extra-peritoneal abscess. We are aware of only five other case reports in the literature describing cutaneous fistulae arising from appendiceal mucinous cystadenocarcinoma.11 12 22–24
Fistulae in these cases arose spontaneously in locally advanced tumours, all of which had also spread into the ascending colon. In our case it is likely that the initial presentation with an abscess represented an infected mucocele, which may have discharged spontaneously through the skin surface if treated conservatively. Previous authors have suggested that such extra-peritoneal rupture of an appendiceal mucocele offers a favourable prognosis by preventing the development of peritoneal carcinomatosis.11 12
Our patient initially underwent a laparoscopic appendicectomy. Following the histological diagnosis she was taken back to theatre for a right hemicolectomy and lymph node clearance. Nitecki et al6
reported one of the largest case series of appendiceal adenocarcinomas and advocate right hemicolectomy for all patients with mucinous adenocarcinoma. Their data show a survival advantage of hemicolectomy over appendicectomy alone (5-year survival, 73% vs 44%, p<0.01). Hemicolectomy performed as a second procedure following appendicectomy (as in our patient) resulted in an up-staging of 38% of tumours. Nitecki et al
also reported synchronous second primary malignancies in a large proportion (35%) of patients and suggest close surveillance for synchronous or metachronous tumours, particularly in the gastrointestinal tract. A later meta-analysis of 284 patients with appendiceal mucinous adenocarcinoma also showed a significant survival advantage of right hemicolectomy over appendicectomy.25
Sugarbaker has demonstrated increased survival in patients undergoing hemicolectomy as a single operation compared to those undergoing a staged procedure for appendiceal mucinous adenocarcinoma.26
Current American College of Surgeons' guidelines recommend right hemicolectomy for all non-carcinoid appendiceal tumours with appendicectomy alone reserved for carcinoid tumours less than 1 cm in diameter.27
- Appendiceal tumours can present with unusual signs and symptoms related to the propensity of mucinous tumours to form fistulae.
- Right hemicolectomy is required to treat and stage appendiceal adenocarcinoma.
- Mucinous adenocarcinoma carries a risk of developing peritoneal carcinomatosis.
- The presence of mucin in association with appendicitis should lead the operating surgeon to suspect adenocarcinoma. In such cases it is important to avoid contamination of the peritoneal cavity with mucin. We also suggest obtaining a cytological analysis of the mucin as the presence of carcinoma cells confirms appendiceal adenocarcinoma rather than pseudomyxoma peritonei.
- Extra-peritoneal rupture of mucinous tumours may offer a more favourable prognosis by preventing the development of peritoneal carcinomatosis.