Skin metastasis from the spindle cell component in rectal carcinosarcoma

Carcinosarcomas are rare tumors, which are usually composed of carcinomatou s areas close to or intermixed with sarcomatous components. Only 6 cases of carcinosarcoma of the colon have been reported in the English literature p reviously. We describe the 7th case, an 82-year-old man with a skin metasta sis from the spindle cell component of a rectal carcinosarcoma. On rectal e xploration, a large, firm tumor was palpated 2cm from the anal verge. Endos copic examination revealed a tumor projecting into the lumen, and hemorrhag e from the tumor surface. We performed a low anterior resection. The resect ed specimen contained an ulcerative lesion with a round wall in continuity with a papillary tumor. Carcinoma and sarcoma components existed concomitan tly along with transitional features. Immunohistochemistry disclosed immuno reactivity for vimentin in most of the spindle cell areas. Carcinoembryonic antigen was positive in the adenocarcinomatous component. One month after surgery, the patient developed a skin metastasis on the back. The skin biop sy specimen contained proliferating spindle cells almost identical to those of the primary lesion. The patient died of carcinosarcoma 6 months after s urgery. In this paper, we review 7 cases of colorectal carcinosarcoma, incl uding our patient, who is only the 7th such reported case.