Pseudoadenoid cystic carcinoma of the breast.

An example of a cribriform intraductal carcinoma that closely resembled adenoid cystic carcinoma is described. The true nature of the tumor was revealed by electron microscopy and the case is used to demonstrate that the diagnosis of this tumor cannot be safely made by routine histologic techniques alone. Review of conflicting views othe value of mucin histochemistry expressed in the literature suggest that ultrastructural examination is a useful alternative tool in the differentiation of adenoid cystic carcinoma of the breast from cribriform intraductal carcinoma.