Interobserver agreement of the Nottingham histologic grading scheme for infiltrating duct carcinoma breast.

Interobserver agreement of the histologic grading scheme for infiltrating duct carcinoma (IDC) of breast was assessed. Three pathologists independently evaluated histologic grade using the modified Bloom and Richardson histological grading system on 40 cases of IDC breast. Pairwise K value for agreement ranged from 0.68-0.83 (median 0.68) for histological grade suggesting substantial agreement. Generalized K values were 0.54, 0.34 and 0.36 for tubule formation, nuclear pleomorphism and mitotic count respectively indicating moderate and fair agreement. Similar levels of agreement were obtained specially in the final histologic grade between pathologists routinely reporting histopathology material and one pathologist who was not. This was achieved by use of precise guidelines. The ease with which this grading system could be applied by pathologists on histopathology material will greatly help its acceptability in routine histopathology.