Mammographically occult breast cancer. A pathologic and radiologic study.

Fifteen mammographically occult breast cancers, 3 of which were preinvasive and 12 invasive, and 52 breast cancers, which presented only microcalcifications mammographically without an associated tumor shadow (33 preinvasive and 19 invasive), were reviewed pathologically and radiologically. This study suggests that most of the preinvasive cancers, without mammographically significant calcifications, are, and some of the invasive cancers situated in dense breasts may be, mammographically occult. The mean diameter of the five mammographically occult invasive ductal carcinomas and the five invasive lobular carcinomas was 20 mm and 50 mm, respectively. Histologic characteristics, which may explain why invasive lobular carcinomas could be occult mammographically, even in an advanced stage, include a diffuse invasive pattern and, frequently, a poor desmoplastic reaction in contrast to the invasive ductal carcinomas. The implications of mammographically occult cancers on management of symptomatic and asymptomatic patients are discussed.