Histologic grading in breast cancer - Reproducibility between seven pathologic departments

Histologic grade, including tubular formations, nuclear grade, and mitotic activity, is a well-documented prognostic factor in breast cancer. In compa rison with other prognostic parameters, the evaluation of histologic grade is cheap and can be performed, in principle, in all cases of breast cancer. One possible disadvantage is that the evaluation may vary between differen t pathological departments. The aim of the present work was therefore to st udy the reproducibility of the histologic grading system by distributing ha ematoxylin-erythrosin-stained slides from 93 invasive breast cancers to the seven pathology departments within the southern healthcare region of Swede n. The evaluation was performed blindly and without any knowledge of other clinical parameters. In 31% of the cases the same histologic grade was obta ined for all departments. The overall mean kappa was 0.54, indicating a mod erate reproducibility. Of the three factors included in histologic grade, t he agreement was best for tubular formations and poorest for nuclear grade and mitotic activity. The overall moderate reproducibility should be consid ered when the clinical usefulness of histologic grading is compared with ot her prognostic instruments.