Correlation between original biopsy pathology and mohs intraoperative pathology

BACKGROUND The pathology observed on initial biopsy specimens for nonmelanoma skin cancer (NMSC), specifically the tumor subtype, weighs heavily into the selection of the treatment modality. Recognizing aggressive features on intraoperative Mohs micrographic surgery (MMS) frozen sections that were not indicated on initial biopsy reports is not uncommon. To date, there is limited data describing this discrepancy. OBJECTIVE To investigate the frequency and nature of incongruity between the pathology seen in initial biopsies and intraoperative Mohs sections, providing information that will potentially impact skin cancer treatment and biopsy recommendations. METHODS Retrospective chart review of cases of NMSC referred for MMS at the authors' institution over a 1- year period, recording changes between tumor subtypes observed at biopsy and those observed during MMS. RESULTS Cases (50.5%) (n = 163) changed aggressiveness. Of these, 33% (n = 108) were more aggressive, whereas 17% (n = 55) were less aggressive. CONCLUSION A substantial discrepancy was observed between preoperative biopsy and intraoperative pathology, including a significant portion tumors that became more aggressive. These results suggest that treatment modalities without margin control may not provide adequate treatment for a considerable number of NMSC based on preoperative tumor type alone.