Synchronous rectal adenocarcinoma and anal canal adenocarcinoma.

It is difficult to distinguish a rectal carcinoma with anal metastases from coexistent synchronous anorectal carcinomas. The therapeutic strategy for rectal and anal carcinoma is so different that it should be clearly identified. Here, we report on the case of a 63-year-old man who presented with an upper-third rectal adenocarcinoma. Five months after resection, he developed an adenocarcinoma in the anal canal. The histological slides of both tumors were reviewed and immunohistochemical studies for cytokeratins (CKs) 7 and 20 were performed. The index tumor demonstrated CK 7-/CK 20+ and the second showed CK7+/CK20+. For this reason, we believe the present case had synchronous adenocarcinomas arising from anal canal and the rectum separately. It is very important to differentiate the anorectal lesions pathologically because of the impact on the therapeutic options available, especially for the lesion arising in the anal canal.