Mucin histochemistry of mucous carcinomas of breast and colon and non-neoplastic breast epithelium.

Although epithelial mucin has been demonstrated in ordinary mammary duct carcinomas, it is formed profusely in the uncommon mucous carcinomas. A histochemical study of mucous carcinomas of the breast and colon showed that both types produce similar mucins, viz, acid and neutral, although the mammary carcinomas produce more neutral mucin and small amounts of sulphated mucins are produced by colonic tumours. Similar studies on sections of normal breast and cystic mammary dysplasia have shown that intracellular neutral mucin was present in the ducts and lobules, and that intracellular acid mucin was present within cells of the terminal ducts and lobules. It was demonstrated enzymatically that the acid mucins produced by the normal and neoplastic tissues is sialic acid. Hence it can be shown that the mucin produced by mucous carcinomas is of epithelial rather than connective tissue type. It is contended that mucous carcinoma of breast arises by metaplasia of duct cells that have already undergone malignant change and not from the lobules of the breast.