Accuracy of diagnosis of benign skin lesions in hospital practice: a comparison of clinical and histological findings

Abstract

Demand for surgical removal of presumed benign skin lesions is increasing. Our aim was to see whether the practice of sending every skin specimen for histological review is necessary in a hospital-based dermatology department. We first reviewed the histological findings of 1000 lesions removed between 1990 and 1992 where a firm clinical diagnosis of a benign melanocytic naevus (BM; n = 250), seborrhoeic keratosis (SK; n = 250), viral wart (VW; n = 250) or skin tag (n = 250) had been made. Next, we perused the original clinical diagnosis made for all histologically proven malignant melanomas (MM) between 1968 and 1993, to see whether they had been misdiagnosed as one of the above four common benign lesions. Histology confirmed the clinical diagnosis in 89% of presumed BM, 89% of presumed SK, 83% of presumed VW and 81% of presumed skin tags. Common causes of misdiagnosis were other benign lesions: 52% of incorrectly diagnosed BM were SK and 30% of incorrectly diagnosed SK were BM, while 38% of incorrectly diagnosed VW were SK. A total of seven malignant tumours (six basal cell carcinomas, one squamous cell carcinoma) were misdiagnosed clinically, one as BM, three as VW, and two as SK, but no malignant lesions were mistakenly diagnosed as skin tags. Review of 238 histologically proven malignant melanomas revealed a prior clinical diagnosis of BM in 9% and SK in 0.8%, but none were clinically misdiagnosed as skin tags or VW. Hence, in a hospital setting, a firm clinical diagnosis of a skin tag did not lead to missed malignancy, and routine histological confirmation of these lesions appears unnecessary. However, in the case of BM and SK, and where clinical doubt exists, histological review remains essential.