EXPRESSION OF THE PS2 PROTEIN AND CORRELATION WITH ESTROGEN-RECEPTOR STATUS IN FINE-NEEDLE ASPIRATES FROM BREAST CARCINOMAS

A series of 36 cases of breast carcinomas diagnosed by fine-needle asp iration were investigated for the presence of estrogen receptors (ER) and the estrogen-induced pS2 protein. Immunocytochemically ER could be demonstrated in 28 aspirates, whereas eight were negative. These eigh t were also negative for the pS2 protein. In addition three aspirates with a low score for ER and five with a high score for ER were found n egative for pS2. Thus, of the 36 cases, 20 were found to express the p S2 protein. The presence of the pS2 protein in the tumor cells is beli eved to be a marker of a functional estrogen regulatory system and its demonstration may therefore predict clinical responsiveness to hormon al therapy. (C) 1994 Wiley-Liss, Inc.