Abstract
To clarify skin tumor incidence and to estimate the proper diagnosis rate, we analyzed the results of skin lesions excised at Showa University Fujigaoka Hospital. A total of 2,504 lesions were obtained from 2,449 patients （1,171 men and 1,278 women; age 11 months to 99 years; mean 56.5 years old） from January 2008 to December 2017; 2,504 and 1,837 （73.4％） were benign tumors, 590 （23.6％） were malignant tumors, and 77 （3.1％） were non-neoplastic lesions. Among the 1,837 benign lesions, epidermal cysts （455 and 24.8％） were the most common, followed by nevus cell nevi （379, 20.6％） and seborrheic keratoses （225, 11.9％）. Among the 590 malignant tumors, basal cell carcinoma （163, 27.6％） was the most frequent, followed by actinic keratosis （132, 22.4％） and Bowen disease （91, 15.4％）. In determining the incidence of malignant tumors by age group, the incidence rate was below 10％ in those less than 50 years old, compared with the 13.9％, 22.5％, 43.0％, and 66.1％ in for those in their 50s, 60s, 70s, and over 80 years old, respectively. The concordance rate between clinical and histopathological diagnosis was 93.3％ （1,762/1,889） for benign tumors and 87.1％ （527/605） for malignant tumors. Of those clinically diagnosed as benign tumors or non-neoplastic lesions, 62 were diagnosed as malignant tumors histopathologically. These included 10 cases of squamous cell carcinoma, 10 malignant melanomas, and 9 basal cell carcinomas. Our data suggest that such discrepancies occur by the following lesions: early-stage tumors, nodes with hemorrhage, pigmented patches on fingers and toes, and tumors arising from uncommon sites, in which clinical diagnosis requires particular close attention to improve the diagnostic accuracy.
