Anal canal adenocarcinoma with MUC5AC expression suggestive of anal gland origin

Anal canal adenocarcinomas arising in the anal ducts or glands are very rare neoplasms, and few useful immunohistochemical markers of these carcinomas are known to date. A 57-year-old man presented with anal bleeding, difficulty of defecation, and anal pain. Macroscopic findings of the surgically resected material showed circular stenosis of the anal canal. The mucosal surface was generally intact, but focal ulceration was seen. Microscopically, the proliferation of adenocarcinoma cells with mucin production was observed in the submucosal and muscular layers. The special stains of periodic acid–Schiff (PAS) and Alcian blue confirmed the presence of neutral and acid mucin. Immunohistochemically, normal rectal-type mucosa and normal anal ducts/glands showed the patterns of cytokeratin 7 (CK7)(−)/CK19(+, focal)/MUC5AC(−) and CK7(+, diffuse)/CK19(+, diffuse)/MUC5AC(+, focal), respectively, and neoplastic cells showed the pattern of CK7(+, diffuse)/CK19(+, diffuse)/MUC5AC(+, focal). Finally, our preliminary report suggests that the immunohistochemical combination of CK7, CK19, and MUC5AC may be an available marker for adenocarcinoma of anal ducts/glands origin.