Poorly differentiated small cell neuroendocrine (NE) carcinoma of the
colon and rectum is a rare primary epithelial malignancy at this locat
ion, A case of a highly aggressive NE tumor of small cell type, combin
ed with non-invasive well-differentiated papillary adenocarcinoma in v
illous adenoma is reported, The patient died rapidly with massive and
progressive liver metastasis, The tumor cells were argyrophilic and di
ffusely immunoreactive for neuron-specific enolase and synaptophysin.
Ultrastructural analysis disclosed NE-type cored granules in most of t
he small tumor cells. NE tumors of the colon and rectum are briefly re
viewed.