Squamous carcinoma of the colorectum and its genesis.

A case of pure aquamous carcinoma of the rectum is presented, and the literature reviewed. Squamous carcinomas of the colorectum are rare tumours which have clinicopathological features in common with adenocarcinomas. Evidence is presented to support the proposal that most tumours of the large intestine that consist partly or completely of squamous elements arise from areas of squamous differentiation in pre-existing adenomas. The pathogenesis of squamous carcinoma and adenosquamous carcinoma appears to be similar to that of adenocarcinoma.