The Assessment of Histological Differentiation in Breast Cancer*

Morphological tumour differentiation has been shown in numerous studies to give a good prediction of prognosis in breast cancer. In the Nottingham/Tenovus study, tumour differentiation (histological grade) is assessed as part of a routine analysis of potential prognostic factors. Three features are analysed, the degree of tubule formation, variation in the size and shape of nuclei and mitotic rate. Each feature is given a score of 1-3 and grade is assigned as follows: Grade I, well differentiated, 3-5 points; Grade II, moderately differentiated, 6-7 points; Grade III, poorly differentiated, 8-9 points. Histological grade has been assessed in 625 patients with primary breast carcinoma and there is a strong correlation with prognosis; patients with well differentiated tumours have a significantly better survival than those with poorly differentiated tumours (P less than 0.0005). Grade forms an important part of the Nottingham/Tenovus prognostic index together with tumour size and lymph node stage. It is suggested that factors such as these should be used to stratify patients for appropriate therapy.