A comparison of five immunohistochemical biomarkers and HER‐2/neu gene amplification by fluorescence in situ hybridization in white and Korean patients with early‐onset breast carcinoma

BACKGROUND The objective of this article was to compare five tumor markers between white women in the U.S. and native Korean women with early‐onset breast carcinoma. METHODS Sixty Korean women who were diagnosed with breast carcinoma at age 45 years or younger and 60 white women with breast carcinoma who were matched by age were selected for this study. The median age of both groups was 37 years. Paraffin embedded blocks of the primary tumor were processed for immunohistochemical staining of estrogen receptor (ER), progesterone receptor (PR), p53, cyclin D1, and HER‐2/neu. RESULTS The proportion of tumors that stained positive for ER, PR, p53, and cyclin D1 in the Korean women were 47.5%, 42.4%, 28.8%, and 40.9%, respectively; in the white women, the proportions were 43.9%, 52.6%, 21.1%, and 59.1%, respectively. The differences between the white patients and the Korean patients were not statistically significant with respect to any of those variables. A significant difference was found in the expression of HER‐2/neu. Specifically, positive HER‐2/neu status was observed in 47.5% of Korean women, compared with overexpression in only 15.8% of white women (P < 0.001). Fluorescence in situ hybridization analysis for HER‐2/neu gene amplification on all HER‐2/neu positive samples that scored 2 + and 3 + demonstrated a significant difference (P = 0.007) in gene amplification between the two populations. Differences in HER‐2/neu positivity were observed for the entire cohort as well as among the subsets of patients with negative and positive lymph node status. No association was found between immunoreactivity for the five markers and axillary lymph node metastasis. CONCLUSIONS The findings of high positivity of HER‐2/neu expression and gene amplification in Korean women with early‐onset breast carcinoma may have potential implications for local and systemic management of breast carcinoma, especially anti‐HER‐2/neu therapy for patients with hormone receptor negativity. Further research will be needed to identify biologic and genetic factors and their effects on the survival between different racial groups. Cancer 2003. © 2003 American Cancer Society. DOI 10.1002/cncr.11703 The authors compared five tumor markers between Korean women and white women in the U.S. with early‐onset breast carcinoma. There were high levels of positivity for HER‐2/neu in the Korean cohort, which may have potential implications for local and systemic management of breast carcinoma.