Signet-ring cell adenocarcinoma of rectum: a histological, histochemical and electron microscopic study.

A signet-ring cell adenocarcinoma of rectum removed from a 71-year-old woman was examined by light and electron microscopy. Most of the mucin in the signet-ring cells was of the neutral type, although acidic, mostly non-sulphated, mucin was also present. Three other types of neoplastic cells. The similarities between this tumour and tumours described in the stomach, appendix and breast care discussed.