Immunohistochemistry of primary breast tumors from four different patients. A-E: ER- and PR-positive lobular breast tumor, grade 2. F-J: ER- and PR-positive ductal breast tumor, grade 1. K-O: ductal breast cancer, also ER- and PR-positive, grade 1. P-T: ductal tumor, ER- and PR-positive, grade 2. As in Fig. 5, all tumors are stained for both L7-2 (A, F, K.P) and L7-3 (C, H, M, R) epitopes in the absence of KLH preincubation, or in its presence (B, D, G, I, L, N, Q, S). Negative controls for both epitopes are also shown (E, T: preimmune serum for L7-2.R2; J, O: preimmune serum for L7-3.R3). Other controls were similar (not shown). Note that the weak, but specific immunostaining of the epithelial tumor cells (e.g. in M and R; arrowheads and elsewhere) was not suppressed by preincubation of the primary antisera with KLH. Scale bar = 50 μm.