SMALL-CELL NEUROENDOCRINE CARCINOMA OF THE RECTUM

Poorly differentiated small cell neuroendocrine (NE) carcinoma of the colon and rectum is a rare primary epithelial malignancy at this location, A case of a highly aggressive NE tumor of small cell type, combined with non-invasive well-differentiated papillary adenocarcinoma in villous adenoma is reported, The patient died rapidly with massive and progressive liver metastasis, The tumor cells were argyrophilic and diffusely immunoreactive for neuron-specific enolase and synaptophysin. Ultrastructural analysis disclosed NE-type cored granules in most of the small tumor cells. NE tumors of the colon and rectum are briefly reviewed.