Interobserver reproducibility of the Lagios nuclear grading system for ductal carcinoma in situ

Several studies have shown an association between high nuclear grade or nec rosis of ductal carcinoma in situ (DCIS) lesions and the risk of local dise ase recurrence in patients with DCIS treated surgically with less than mast ectomy. Although criteria for separating low from high nuclear grade lesion s have been published, no information exists regarding interobserver reprod ucibility (IR). To assess IR in the classification of DCIS, six surgical pa thologists from four institutions used the Lagios grading system to grade 1 25 DCIS lesions. Before meeting to evaluate the cases, a training set of 12 glass slides, including cases chosen to present conflicting cues for class ification, was mailed to the participants with a written criteria summary. This was followed by a working session in which criteria were reviewed and agreed on. The pathologists then graded the lesions independently. The area of interest was marked on each slide before grading. After initial grading , the pathologists met again to resolve discrepant lesion classifications. A complete agreement among raters was achieved in 43 (35%) cases, with five of six raters agreeing in another 45 (36%) cases. In no case did two rater s differ by more than one grade. The pairwise kappa agreement values ranged from fair:to substantial (0.30 to 0.61). Generalized kappa value indicated moderate agreement (0.46, standard error = 0.02). kappa statistics for the distinction between grades 1 and 2 and 2 and 3 were 0.29 and 0.48, respect ively, (standard error = 0.02). Only one of the six raters differed signifi cantly in scoring. With adherence to specific criteria, IR in the classific ation of DCIS cases can be obtained in most cases. Although these pathologi sts made a few grading system modifications, further refinements are needed , especially if grading will influence future therapy. HUM PATHOL 30:257-26 2. Copyright (C) 1999 by W.B. Saunders Company.