Abstract: | A 46-year-old man with a suspected malignant submucosal tumor received a transabdominoperineal rectal amputation. The histologic diagnosis was xanthogranuloma. The differentiation of xanthogranuloma from malignant fibrous histiocytoma and other histiocytic tumors is difficult in the preoperative stage. Malignant fibrous histiocytoma can be diagnosed histologically by the presence of pleomorphism, mitotic activity, hyperchromatism, and a storiform pattern of cell arrangement. Moreover, some xanthogranulomas are also thought to have malignant potentiality and surgical resection is regarded as the preferred treatment. As for prognosis, the patient has lived for three years after the operation but further follow-up is thought to be necessary. |