A case of perianal mucinous adenocarcinoma arising in a fistula-in-ano. A clue to the early pathologic diagnosis.

The author presents a case of perianal mucinous adenocarcinoma supervening on a long-standing fistula-in-ano. Features of this unusual neoplasm are reviewed. This case is of particular interest because a review of surgical material from a fistulotomy performed two years before the diagnosis of adenocarcinoma provides a clue to the early diagnosis. The clue is the presence of globules of mucin present in the granulation tissue and free on the slide. Fifty routine fistulotomy or fistulectomy specimens did not contain mucin globules. Recognition of the appearance of these mucin globules in fistulectomy or fistulotomy specimens can alert the pathologist to the possibility of perianal mucinous adenocarcinoma, resulting in earlier diagnosis and treatment.