Breast carcinoma is the most common malignant tumour and the main cause of carcinoma death in women. There has been a sharp increase in the detection of breast carcinoma, although mortality is still unvaried. In the last ten years the incidence of breast cancer measuring less than 1 cm, corresponding to pT1a, pT1b in TNM stadiation, has greatly increased. The present study describes the biologic characterisation of small breast carcinomas. The Nottingham/Tenovus Primary Breast Cancer Study stated that tumour size is a significant, independent factor for breast cancer prognosis. Cases were selected among formalin-fixed, paraffin-embedded tissues from 360 ductal breast cancers. In one-half of cases, the tumour was less than 1 cm in diameter, pT1a- pT1b; in the other half the tumour size was greater than 1 cm, but less than 2 cm, pT1c. Histological grading was assessed with the Scarff-Bloom-Richardson method, without Nottingham grade. Immunohistochemical determinations for ER, PgR, Ki-67, Her-2/Neu, CD34, p53, EGFR were done with an automated method. From the above analyses, it was demonstrated that the tumour size is indeed an important prognostic factor, particularly in cases without lymph node metastasis (N0). In particular, we observed significant differences between pT1a-b and pT1c cases, confirming that tumour size is an important criterion for prognostic valuation in ductal breast cancer without lymph node metastasis.