Benign fibrous histiocytoma presenting as anal canal polyp: first case report.

Nonepithelial and nonmelanocytic anal neoplasms are uncommon. The majority are mesenchymal tumors, most of which are malignant sarcomas, particularly leiomyosarcomas and gastrointestinal stromal tumors. Benign mesenchymal anal neoplasms are even rarer. The most common reported cases were anal leiomyomas, granular cell tumors, fibroadenomas, and xanthogranulomas. Benign fibrous histiocytomas (BFHs) or dermatofibromas are common mesenchymal cutaneous tumors that occur in different sites and at any age. Review of the literature did not show previous reports of BFH arising in the anal canal region. We report the first case of a solitary BFH, an unexpected occurrence of a common tumor type presenting as a polyp in an unusual site such as the anus. This rare occurrence can present diagnostic challenges for the surgeons and pathologists. Clinically, it can be confused with the usual anal tags, fibroepithelial polyps, or hemorrhoids. Benign fibrous histiocytoma is a neoplasm with a potential of local recurrence and, therefore, carries certain clinical implications for the patients' management and follow-up when compared with the common nonneoplastic causes of anal polyps such as the anal tags of anal fissures, hemorrhoids, or fibroepithelial papilla. Histologically, it should be differentiated from other histiocytic lesions. This can be resolved by the application of certain histologic features with the appropriate immunohistochemical markers taken within the correct clinical context.