IMMUNOHISTOCHEMICAL DETECTION OF HER2/NEU IN PATIENTS WITH AXILLARY LYMPH-NODE NEGATIVE BREAST-CARCINOMA - A STUDY OF EPIDEMIOLOGIC RISK FACTORS, HISTOLOGIC FEATURES, AND PROGNOSIS

Background. Numerous studies have examined the prognostic significance of HER2/neu (HER) expression in patients with axillary lymph node negative breast carcinoma. Although some investigations suggest that the presence of the altered expression of HER is prognostically unfavorable, the subject remains controversial. This study explores the interaction of HER with three aspects of axillary lymph node negative breast carcinoma: epidemiologic risk factors, tumor histopathology, and prognosis. Methods. Immunohistochemical staining for HER was performed on 10% formalin fixed paraffin embedded primary carcinomas from 440 patients with negative axillary lymph nodes with a median follow-up of 119 months. Results. The immunohistochemical expression, or lack thereof, of HER did not prove to be prognostically significant in this group of patients with axillary lymph node negative breast carcinoma. There was also no consistent association with epidemiologic risk factors. The most striking results concerned the relationship of HER to histopathologic features of the carcinomas. Medullary carcinoma differed from other tumor types because it was HER(+) substantially less often (10%) than were other ductal (49%) or lobular (43%) carcinomas. Conclusion. The results obtained in this study suggest that the immunohistochemical demonstration of HER is not a reliable prognostic indicator for patients with axillary lymph node negative breast carcinoma. This marker was not associated with major epidemiologic risk factors; however, there was a significant correlation between HER and the phenotypic features of breast carcinoma because medullary carcinoma is rarely HER(+). Although the associations may not be a strong enough basis for refining the classification of breast carcinoma, they could be useful for diagnosing individual patients. The changes in HER that are detectable by the immunohistochemical methods used in this study probably do not occur in the earliest stages of mammary carcinogenesis.