Histologic subtypes of invasive lobular carcinoma in correlation with tumor status and hormone receptors.

Invasive lobular carcinoma is a distinct biological entity with several histologic variants the prognostic value of which is not fully elucidated. The aim of this study was to determine the immunohistochemical expression of estrogen receptors (ER) and progedterone receptors (PR) in subtypes of lobular breast carcinoma (classic and variant types) and to correlate them with clinical and tumor parameters. Fifty lobular carcinomas, i.e. 33 classic and 17 variant, were analyzed. The classic type was more common (66%) and found in older women (61 years of age), smaller in size (1.5 cm), with N0 status and modestly positive ER and PR. The variant types were more frequent in younger women (55 years of age), larger in size (2.5 cm), with N1 status and maximal positive ER and PR. ER was expressed in 82% and PR in 78% of all tumors, mostly with maximal expression. Only one tumor of the classic type was HER/2neu 3+, ER and PR-. ER expression was significantly associated with a decreased incidence of other proliferative lesions (P=0.043). The total sample and the classic type were characterized by a significant positive correlation between ER and PR (P=0.004) and between tumor size and N status (P=0.005), and by negative correlation between HER/2neu and N status (P=0.042). In variant types, larger tumors were related to higher N (P=0.021), while higher ER expression was associated with smaller tumors (P=0.044). The study indicated distinct biological features oflobular carcinoma subtypes and the need for a more selective therapeutic approach.