Malignant tumors in the rectum simulating solitary rectal ulcer syndrome in endoscopic biopsy specimens.

Patients with solitary rectal ulcer syndrome (SRUS) frequently present with a mass that can be misinterpreted as cancer. In contrast, the occurrence and characteristics of SRUS-like histopathology produced by underlying malignancy have not been reported in detail. We report seven patients whose rectal mass that was induced by infiltrating carcinoma showed only histopathologic changes of SRUS on initial mucosal biopsy specimens. Carcinoma was evident in subsequent specimens after one to five repeat biopsies with delay in diagnosis from 1 week to 18 months in six patients. In one patient, infiltrating carcinoma was suggested on the first biopsy specimen by immunohistochemistry for cytokeratin. Three of the patients had primary rectal adenocarcinoma, two had metastatic carcinoma from stomach or ovary, and two had direct invasion of anal squamous cell carcinoma or prostatic adenocarcinoma. We conclude that the histopathology of SRUS may occasionally represent a characteristic but nonspecific mucosal reactive change to a deeper seated malignancy. The terminology "solitary rectal ulcer syndrome/mucosal prolapse changes" with a cautionary note may be useful for reporting biopsy results to emphasize the possibility of underlying primary or metastatic malignancy in the differential diagnosis.