MEDULLARY CARCINOMA OF THE BREAST - PREVALENCE AND PROGNOSTIC IMPORTANCE OF CLASSICAL RISK-FACTORS IN BREAST-CANCER

In an earlier study of 235 breast cancers with medullary features, we concluded from a multivariate Cox regression analysis that only four h istopathological features contained significantly positive prognostic information. In the present study, continuing our work on the same pop ulation base, we used these histological characteristics (predominantl y syncytial growth pattern, no tubular component, diffuse stromal infi ltration with mononuclear cells and sparse necrosis (<25%), as diagnos tic criteria for medullary carcinoma of the breast (MC). We found a si gnificantly better prognosis for patients with MC than those with non- medullary carcinoma (NMC) or infiltrating ductal carcinoma (IDC). All tumours in the MC group were grade II or III (96% grade III). A signif icantly different distribution of general risk factors such as lymph n ode status, invasion, steroid receptor status, and menopausal status, was found between the group of MC and the control group of IDC grades II + III. Further, general risk factors, which are found to be of majo r prognostic importance in IDC, had little prognostic impact in MC. We found MC to be biologically unique, and patients with MC have a bette r than average prognosis compared to that of IDC. We propose a new his tological definition of MC, but stress that prospective studies have t o be performed.