Histopathological Diagnosis of Lesions Clinically Diagnosed as Melanocytic Nevus

Abstract

We reviewed and analysed histopathological diagnoses of 13,594 specimens, that had been clinically diagnosed as melanocytic nevus and histopathologically diagnosed in the Sapporo Institute for Dermatopathology. They included 3,497 specimens (5.7%) from male patients and 10,097 specimens (74.3%) from female patients. The lesions were most frequently located on the face (53.8%). Histopathologically, 11,840 specimens (87.1%) were diagnosed as melanocytic nevus. The cases not diagnosed as melanocytic nevus included 8.6% benign epithelial neoplasms, 2.4% benign non-epithelial neoplasms, and 1.3% malignant neoplasms. Among the malignant neoplasms, the most frequent (0.9%) diagnosis was basal cell carcinoma; 16 specimens (0.1%) were malignant melanoma in situ, and 13 cases (0.1%) were malignant melanoma. The concordance rate between clinical and histopathological diagnoses was high for the lesions on the lower limbs (92.3%) and the face (89.2%), although low for those on the neck (78.2%) and the trunk (79.1%). Malignant neoplasms were frequently located on the face and scalp. The median age at resection of the cases with melanocytic nevus (36.5±15.9 years) was significantly lower than those with another diagnosis (53.3±18.1 years). These data indicate that diagnoses should be confirmed histopathologically in lesions clinically diagnosed as benign melanocytic ones.