Filiform polyposis: a case report describing clinical, morphological, and immunohistochemical findings.

Filiform polyposis (FP) is a rare condition of uncertain pathogenesis, 28 cases of which have been published since it was first described in 1965. It is usually found in association with chronic inflammatory bowel disease, especially Crohn's disease and ulcerative colitis. The condition is characterized by the presence of numerous, densely packed, filiform polyps in the colon, which may resemble villous adenomas on endoscopy. We describe a case of FP occurring in a 33-year-old man with a 5-year history of Crohn's disease, in whom subtotal colectomy was performed because of perforation of the sigmoid colon. Microscopy revealed inflammatory pseudopolyps covered by largely normal and non-dysplastic colonic epithelium. The neuroendocrine system of the intestine in FP was investigated for the first time in this case: marked hyperplasia of endocrine cells immunoreactive for serotonin, somatostatin and enteroglucagon and of neural structures immunoreactive for substance P and vasoactive intestinal peptide was noted in the polyps and the adjacent intestinal mucosa. The patient has experienced no further complications in the 12 months since the operation. Medication administered in FP depends mainly on the nature of the underlying disease, and the amount of information published about this condition is as yet insufficient to allow any one specific type of treatment to be recommended. FP alone is not an indication for bowel resection but complications, such as massive haemorrhage or intestinal obstruction, may necessitate surgical intervention.