Mucinous adenocarcinoma of perianal region: an uncommon disease treated with neo-adjuvant chemo-radiation

Abstract

Mucinous adenocarcinoma of the perianal region is an oncologic rarity posing a diagnostic and therapeutic dilemma for treating oncologists due to very few reported cases without definite therapeutic guidelines. It accounts for 2% to 3% of all gastrointestinal malignancies and are historically known to arise from chronic anal fistulas and ischiorectal or perianal abscesses. We hereby report a sporadic and interesting case of perianal mucinous adenocarcinoma in a 56-year-old male initially treated with alternative medicines and local surgery for recurrent fistula in ano of 2 years duration. He presented with complaints of discharging growth in perianal region, painful defecation associated with occasional blood mixed stools of 6 months duration. Incisional biopsy from the ulcer revealed mucinous adenocarcinoma.Contrast enhanced computed tomography (CT) scan and whole body positron emission tomography (PET) scan showed a localized perianal growth which was further confirmed with colonoscopy. With no pre-set treatment protocol for this rare entity, he was managed with neo-adjuvant concurrent chemoradiation (CCRT) followed by abdominoperineal resection (APR) and adjuvant chemotherapy. Presently he is on 3 monthly follow-up since last 1 year post APR and adjuvant chemotherapy without any evidence of recurrence or distant metastasis. To the best of knowledge, our report may be one of the rarest cases of this disease entity where the duration of anal fistula was merely 2 years in contrast to the established criteria that the fistula precedes carcinoma by at least 10 years.

Mucinous adenocarcinoma within an anal fistula in a patient with Crohn’s disease

“…Anal cancer represents a minority of 2-3% among neoplasms of the gastrointestinal tract. 2,5 Three types of anal canal cancer have been described: intestinal adenocarcinoma, squamous cell carcinoma, and mucinous adenocarcinoma. Only 5-11% of anal cancers correspond to anal mucinous adenocarcinoma.…”

“…Only 5-11% of anal cancers correspond to anal mucinous adenocarcinoma. 2,5 There is no consensus about its origin, pathogenesis or biological behavior. Nevertheless, there is an increase in its incidence when there are chronic concomitant inflammatory conditions such as chronic anal fistula in a patient with Crohn's disease.…”

“…In 1934, Rosser et al, was a pioneer in the description of perianal carcinoma arising from chronic fistula. 3,5 Some authors, like Traube et al, have postulated that this association is due to the need for constant regeneration of the mucosa.…”

“…It is estimated that mucinous adenocarcinoma of the anal canal has an incidence of 0.7% in patients with Crohn's disease. 2,5,6 If it is associated with chronic anal fistula, the average age at which it occurs is between 43 and 53 years old. The mean duration of the fistula in a patient with Crohn's disease before the diagnosis of cancer is 10-20 years.…”

“…The mean duration of the fistula in a patient with Crohn's disease before the diagnosis of cancer is 10-20 years. 5 The risk factors for malignization of the fistula are the degree of associated inflammation, the location, and of least importance the time of evolution. 1 Cancer often goes unnoticed owing to the inflammatory disease itself so a high diagnostic suspicion is necessary, with biopsy being the gold standard for diagnosis.…”