HER2 as a prognostic factor in breast cancer

HER2 amplification/overexpression is a marker of poor prognosis in breast c ancer. The prognostic impact of HER2 positivity is lower in node-negative c ompared with node-positive women. The only significant, independent prognos tic factors in breast cancer are node status, HER2 status and menopausal st atus. HER2-positive tumors also contain p53 abnormalities, tend to be hormo ne receptor and bcl-2 negative, have lymphoid infiltration (LI) and a high mitotic index. Patients with LI who are HER2 positive have a better prognos is than those who are HER2 negative, whereas HER2-positive patients, withou t LI have a significantly worse prognosis than HER2-negative patients. Morp hological and biological alterations appear to identify two categories of b reast tumor. Two hypotheses may explain the progression to two tumor types: (1) atypical ductal hyperplasia (ADH) is a precursor of ductal carcinoma i n situ (DCIS), which is a precursor of invasive ductal carcinoma (IDC); or (2) ADH is a precursor of HER2-negative IDC whereas DCIS is a precursor of HER2-positive IDC. The second theory fits well with two breast cancer subse ts and the characteristics of ADH and DCIS. The first type of IDC occurs in older patients, progresses slowly due to estrogen dependency but is aggres sive long term. The other type progresses rapidly, is HER2 positive and is more likely to occur in young patients. Copyright (C) 2001 S. Karger AG, Ba sel.