[A case of small-cell carcinoma of the rectum].

A case of oat-cell carcinoma of the rectum prompted the authors to undertake a review of the literature. The main histological aspects allowing an accurate diagnosis are stressed. This is a rare form of highly malignant neoplasm of uncertain origin (probably similar to that of carcinoids) with a very marked tendency to metastasize, even to distant organs; it is characterized by substantial cellular polymorphism with small-sized elements, very little cytoplasm, a large hyperchromic nucleus, barely visible nucleoli and histochemical reactions typical of neuroendocrine cells.