Quick detection of nonmelanoma skin cancer by histopathology: feasibility and diagnostic accuracy of immediate cutaneous diagnosis

Abstract

Background: Dermoscopy, diagnostic cytology, confocal microscopy are used to improve diagnostic accuracy. Frozen section techniques have been used to control margins but not for diagnosis. Objectives: We used a new frozen section technique called immediate cutaneous diagnosis for nonmelanoma skin cancer, assessing its feasibility and accuracy in obtaining a result within 15 minutes and recording limitations. Methods and Materials: An observational, prospective clinical study was designed. Biological samples were divided into two: one half was included in paraffin, following the standard procedure, and immediate cutaneous diagnosis was applied in the other. Fresh tissue was examined by frozen sections with perpendicular slides and staining with toluidine blue. Two hundred and sixty patients were enrolled. Results: Immediate cutaneous diagnosis-toluidine blue had a sensitivity of 98.7% (95%CI: 93.0-100%) and a specificity of 92.6% (95%CI: 87.4-96.1%) in detecting nonmelanoma skin cancer. Inter-rater agreement between two dermatopathologists using Cohen's kappa was 0.796 (P<0.0001) in a subsample of 101 cases. Immediate cutaneous diagnosis-toluidine blue had a sensitivity for squamous epithelial lesions of 78.3% (95%CI: 63.689.1%) and a specificity of 98.4% (95%CI: 95.5-99.7%).