C-erbB-2 oncogene protein in in situ and invasive lobular breast neoplasia.

Lobular carcinoma in situ (LCIS) has uncertain malignant potential; biologic markers that will identify patients at risk for a poor clinical outcome have been sought actively. Amplification of the c-erbB-2 protooncogene has been correlated with poor prognosis in invasive mammary carcinoma, and immunohistochemical evaluation for expression of the oncogene protein has been correlated with gene amplification. The authors retrospectively evaluated 62 cases of lobular neoplasia for expression of the c-erbB-2 gene product on formalin-fixed, deparaffinized sections, using two monoclonal anti-erbB-2 (p185) antibodies (c-neu Ab3 and m-erb) and one polyclonal anti-erbB-2 antibody (pAb 1) by the avidin-biotin-peroxidase method. All 62 cases were negative with the pAb 1 antibody; one of 62 cases was weakly positive with the c-neu Ab3 in a membranous pattern. Expression of c-erbB-2 gene product was identified on adjacent invasive ductal carcinoma in one case and in adjacent ductal carcinoma in situ in another. None of 15 cases if infiltrating lobular carcinoma was positive with either of the two anti-c-erbB-2 antibodies. Strong positivity was found on benign epithelium in one case, demonstrating epitheliosis. In summary, evidence of expression of the c-erbB-2 gene product was found in one of 57 cases of LCIS and none of 15 cases of invasive lobular carcinoma. This suggests that, in contrast to reported data concerning intraductal and invasive ductal carcinoma, c-erbB-2 oncogene amplification and/or overexpression does not play a significant role in the progression of lobular breast neoplasia.