A prospective study of 232 patients with primary invasive breast cancer (UICC Stages I, II and III) and histologically confirmed axillary node status was carried out to assess the prognostic significance of several readily available clinical and pathological characteristics. In addition to the recognised utility of tumour size and axillary lymph node status, the presence or absence of cohesive clumps of malignant cells in peritumoral vascular spaces (both lymphatic and blood vessels) was found to be prognostically important.