Bilateral breast carcinoma in the female is considered to be an infrequent occurrence. However, one must be careful to exclude those cases in which the involvement of the second breast is actually extension or metastasis from an original primary in the first breast. These are not truly bilateral breast carcinoma cases.
The independent bilateral primary breast carcinoma case must base its classification on pathological microscopic diagnosis and on clinical findings. If each breast carcinoma is of a different cell type there can be no question of the independent origin of these two tumors. The clinical ground on which the above classification rests is the absence of evidence of recurrence, local or regional, of the original breast carcinoma, and the absence of evidence of distant metastases.
There are two categories of bilateral breast carcinoma. One is the simultaneously occurring situation, the other is the successively occurring one. The former situation is
HOFFMAN E. Simultaneous Independent Bilateral Carcinoma of the Breast. Arch Surg. 1960;81(4):671-673. doi:10.1001/archsurg.1960.01300040155030