Intraductal signet ring carcinoma. A hitherto undescribed form of intraductal carcinoma of the breast.

Attention is directed to a unique but apparently heretofore undescribed and overlooked form of intraductal carcinoma of female breast characterized by varying numbers of intraductal neoplastic cells with eccentric nuclei and either ground-glass or optically clear, mucin-containing cytoplasm. Eight examples have been observed in breast tissue submitted consultatively for the distinction of hyperplasia and intraductal carcinoma. This lesion, designated as intraductal signet ring carcinoma, may be found in some of the ducts of otherwise benign fibrocystic disease and radial scars, as well as breasts with other forms of intraductal carcinoma or invasive carcinoma. Four hundred consecutive examples of the latter examined prospectively revealed this intraductal lesion in 12 or 3%. Only 3 of the 12 examples were associated with either pure or combination forms of lobular invasive carcinoma.