Association between tumour characteristics and HER-2/neu by immunohistochemistry in 1362 women with primary operable breast cancer

Aims: To investigate the association between tumour characteristics and HER-2/ neu by immunohistochemistry in primary operable breast cancer. Methods: The association between HER-2/ neu and other clinicopathological factors was evaluated in 1362 consecutive patients with primary breast cancer treated between 2000 and July 2003 in one centre. Microscopic tumour size, tumour grade, lymph node status, patient's age, oestrogen receptor ( ER), progesterone receptor ( PR), and joint ER/PR status were evaluated, using the chi(2) test for univariate analysis and logistic regression for multivariate analysis. The hormone receptors and HER-2/ neu were studied immunohistochemically. Using the HER-2/ neu DAKO scoring system, scores of 0, 1+, or 2+ were defined as negative and 3+ as positive. Data for DAKO scores 2+/3+ versus 0/1+ are also presented. Results: Hormone receptor negative breast cancers were more often HER-2/ neu positive than hormone receptor positive cancers, both for ER (28.7% v 6.8%) and PR (19.9% v 5.9%). In multivariate analysis, both ER, PR, and tumour grade were independently associated with HER-2/ neu. In ER+ tumours, HER-2/ neu overexpression was significantly lower in PR+ than in PR- cases (11.5% v 5.4%). HER-2/ neu overexpression (2.7%) was lowest in the large subgroup of ER+ PR+ tumours with low tumour grade ( grade 1 - 2), comprising 46.1% of all patients. Conclusions: ER, PR, and tumour grade are independent predictors for HER-2/ neu overexpression in women with primary operable breast cancer. ER and PR are negatively associated with HER-2/ neu, whereas tumour grade is positively associated with HER-2/ neu. In women with ER+ tumours, PR status also affects the likelihood of HER-2/ neu expression.