Atypical tumors of the rectum with pathologic correlation.

Although the majority of rectal masses are histologically characterized as adenocarcinoma, there is a wide spectrum of rare, but specific, neoplastic processes that can involve the rectum and present with rectal bleeding. Knowledge of their existence and protean imaging features is crucial for accurate diagnosis and appropriate management. This review article describes the clinical, imaging, and histopathologic characteristics of several pathologically proven rectal lesions, including rectal carcinoid, rectal gastrointestinal stromal tumor, rectal cavernous hemangioma, primary anorectal melanoma, primary rectal lymphoma, and rectal metastases.