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.
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