COMPARISON OF THE PROGNOSTIC VALUE OF SCARFF-BLOOM-RICHARDSON AND NOTTINGHAM HISTOLOGICAL GRADES IN A SERIES OF 825 CASES OF BREAST-CANCER - MAJOR IMPORTANCE OF THE MITOTIC COUNT AS A COMPONENT OF BOTH GRADINGSYSTEMS

The most commonly used system in Europe for breast carcinoma was devel oped by Scarff, Bloom and Richardson (SBR). it was recently modified b y Elston and Ellis and significant improvement in reproducibility has been shown by using precise grading guidelines. This study investigate d whether the use of this new grade (defined as the Nottingham grade, NG) would improve the prognostic stratification of patients. The respe ctive prognostic value of the two grading schemes was compared in a re trospective series of 825 patients uniformely treated for a small inva sive breast carcinoma and followed for a median of 6 years. Univariate and multivariate analysis showed that both histological grades were s trongly correlated to overall and metastasis free survival We have sep arately analysed the prognostic value of each of the three components used to assess the two grading systems and found that the mitotic inde x was the only significant prognostic factor for 5 year survival Univa riate analysis showed the count to be mon discriminant in the NG schem e (p=0.0006) than in the SBR scheme (p=0.04). However, in univariate a nd multivariate analysis, the prognostic value of the global NG was no t significantly better than SBR grade. This may be related in part, to an uneven distribution of cases reflected by a much lower number of c ases with a high mitotic index in the NG system (2%) than in the SBR s ystem (10%). Our study emphasizes the importance of the mitotic count in assessing the prognosis of breast cancers and indicates that the fa ctors which condition this count (tissue processing, microscopic obser vation, threshold) must be well standardized and controlled.