Adenocarcinomas associated with perianal fistulae in Crohn’s disease have a rectal, not an anal, immunophenotype

SummaryAimsPerianal fistulae are often observed in patients with Crohn’s disease (CD), although the development of associated adenocarcinomas is very rare. The origin of adenocar-cinomas in perianal fistulae associated with CD remains controversial and includes adjacent anal glands or rectal mucosa. Here, we attempted to determine the origin.MethodsWe performed immunohistochemical analysis on seven cases of adenocarcinomas in perianal fistulae associated with CD using antibodies against mucins (MUCs), cytokeratins (CKs) and the intestine-specific transcription factor CDX2.ResultsMUC2 and CK20 were expressed in all seven adenocarcinomas examined. MUC5AC/CLH2, MUC5AC/ HGM and CDX2 were positive in four (57%), five (71%), and five (71%) adenocarcinomas, respectively. These proteins were positive in rectal mucosa, and negative in the anal glands. Six of seven adenocarcinomas (86%) were negative for CK7. CK7 was expressed in the anal glands, but not in rectal mucosa.ConclusionsAdenocarcinomas in perianal fistulae associated with CD showed immunohistochemical phenotypes similar to those of rectal-type mucosa, rather than the anal glands. The adenocarcinomas might originate from cells migrating from the adjacent rectal mucosa to the CD- associated perianal fistulae.