Diagnostic concordance among dermatopathologists in basal cell carcinoma subtyping: Results of a study in a skin referral hospital in Tehran, Iran

Background: Basal cell carcinomas (BCC) are the most prevalent among non-melanoma skin cancers (NMSC), which correspond to the most common skin cancers. BCC histopathological subtyping is a problem in therapeutic management. Therefore, we have decided to perform a histopathologic study for better classification of BCCs based on interobserver diagnostic judgment. Methods: We conducted this cross-sectional study on 100 randomly selected pathologically confirmed BCC cases of various subtypes at Razi Hospital, Tehran, Iran during 2013 and 2014. A total of four dermatopathologists independently reviewed each pathology slide to evaluate the interobserver concordance rate. Results: The overall Fleiss’ kappa statistic (kappa) for the BCC subtypes was 0.18 (P<0.001), which indicated slight agreement. We observed moderate agreement on superficial and nodular BCC (kappa: 0.0-0.4); fair agreement on infiltrative and keratotic BCC (kappa: 0.2-0.4); and slight agreement on pigmented, micronodular, and metatypical BCC (kappa: 0.0-0.2). There was moderate agreement diagnosis for the low and high risk growth pattern categories. Conclusion: Overall, we found that the dermatopathologists had inconsistent nomenclature for the BCC subtypes, however they had better agreement for the diagnosis of superficial, nodular, and infiltrative subtypes and the high risk growth pattern.