Histopathological systems of breast cancer classification: reproducibility and clinical significance.

The inter- and intraobserver reproducibilities of the histopathological systems of breast cancer classification suggested by the World Health Organisation (WHO), the Armed Forces Institute of Pathology (AFIP) and Ackerman have been analysed. The reproducibilities of the three classification systems were only "fair" to "moderate" and no correlation with the five-year recurrence rate was found. Our results indicate that these classification systems are without biological significance and are useless for prognosis in the individual patient. When the tumours were classified according to degree of differentiation (high, moderate, low) or graded according to WHO (which includes both differentiation and nuclear atypia), however, there was a significant correlation with the five-year recurrence rate. Yet even such "reduced" subdivisions are of no value in judging prognosis for the individual patient at the time of diagnosis; rather, they are useful only in the follow-up analysis of groups of patients.