Aims: To determine the prognostic usefulness of the Nottingham histological grade (NHG) and its components in a series of 270 patients with stage pT1N0M0 breast cancer with a median follow up of 12.5 years.
Methods: Microscopic slides were re-examined and the degree of tubule formation, nuclear pleomorphism, and mitotic counts were assessed and scored according to the suggested guidelines. The association with cancer specific survival (CSS) was evaluated by univariate and multivariate analyses.
Results: Whereas tumour size, patient age, menopausal status, type of surgery, or adjuvant treatment were not related to prognosis, histological type (p < 0.01) and NHG (p < 0.005) were associated with CSS. When evaluating the components of NHG separately, survival was not related to the score for pleomorphism, but was significantly better in tumours with score 1 or 2 for tubule formation (p < 0.007) and in those with score 1 for mitotic counts (p < 0.006). The two components retained independent significance in multivariate analysis. When the proposed cut off points for mitotic counts were replaced by lower ones based on tertile values, the mitotic index became the strongest prognostic factor (p = 0.0001) and histological type was the only additional factor of independent prognostic significance.
Conclusions: These findings confirm the prognostic value of NHG in pT1N0M0 breast carcinoma, show that the evaluation of tubule formation and mitotic rate provides independent prognostic information, and suggest that the proposed cut off points for mitotic counts may be too high for this particular group of tumours.