DISCORDANCE IN THE HISTOPATHOLOGIC DIAGNOSIS OF MELANOMA AND MELANOCYTIC NEVI BETWEEN EXPERT PATHOLOGISTS

The reliability of a diagnostic test depends on the reproducibility of the result. Many clinical diagnostic tests can be quantified with est ablished ranges and standard deviations. Other tests are more subjecti ve, such as those that depend on analysis of a visual image with an in creased possibility of variance in the result To study this variance, the authors analyzed the performance of expert pathologists in the int erpretation of cutaneous melanocytic tumors. A panel of expert patholo gists was convened to review anatomic pathology specimens from melanoc ytic tumors. Each pathologist submitted five specimens, from which 37 were selected for review. Only one slide was used for each case. All s pecimens were interpreted by each pathologist without consultation wit h each other. fn addition to standard diagnostic term, each specimen w as designated as benign, malignant, or indeterminate. Statistical anal ysis was used to determine the degree of concordance. The combined Ic statistic for the eight observers and three possible outcomes (benign, malignant, or indeterminate) was 0.50. A kappa statistic of this magn itude is defined as being moderate. In 62% of the specimens, there was unanimous agreement or only one discordant designation. Thirty-eight percent had two or more discordant interpretations. No single patholog ist had a disproportionate number of discordant designations. This stu dy mimics the consultation practice of anatomic pathology and shows th e variability and discordance in diagnostic language and designation o f biological behavior The results suggest the criteria for the diagnos is of melanomas and melanocytic nevi need to be refined and more consi stently applied. Copyright (C) 1996 by W.B. Saunders Company