[Carcinosarcoma of the sigmoid colon with micropapillary pattern: a case report]

Carcinosarcomas are very rare malignant tumors showing both mesenchymal and epithelial differentiation. They most commonly occur in the head and neck region. Few cases were described in the colon associated with very aggressive course. Micropapillary variant is also very rare in the colon and associated with poor prognosis. We report an unusual case of carcinosarcoma of the colon with micropapillary features and psammomatous calcification in an 83-year-old female patient. Tumor was located in the sygmoid colon and measured up to 3.8 cm in the largest diameter. Microscopically it was composed of glandular structures and micropapillary formations with psammomatous calcifications and solid areas built up of spindle cells with focal areas of cartilaginous differentiation. Glandular and micropapillary components immunohistochemically showed positive staining for cytokeratin and EMA while mesenchymal areas were positive for vimentin. The tumor was spreading through the whole thickness of the wall into adjacent fat tissue. Metastases in regional lymph nodes were composed entirely of glandular component. To the best of our knowledge, this is the first case of carcinosarcoma of the colon showing micropapillary features and psammomatous calcification.