The burden of cutaneous adnexal carcinomas and the risk of associated squamous cell carcinoma: a population-based study

Background: Recent studies have shown an increasing incidence of cutaneous adnexal carcinomas (CACs). Objectives: The aim of our study was to evaluate incidence and survival for cases of CACs and investigate their association with other skin neoplasms. Methods: We conducted a population-based study. Data on incident cases of CACs were obtained from the Tuscany Cancer Registry between 1985 and 2010. In order to determine whether the occurrence of squamous cell carcinoma (SCC) among patients with CAC is higher or lower than expected in the general population, the standardized incidence ratio (SIR) was calculated. Results: A total of 242 patients with CAC were observed; the age-standardized incidence rate was 3·8 cases per million person-years. From 1997 to 2010 crude incidence rates increased by 159%. Age-specific incidence was higher in men over 80 years old than in women of the same age and younger individuals. Carcinomas of sweat gland origin prevailed; the most common histotype was porocarcinoma and the most frequently affected site was the head/neck. Overall, 88% of CACs were diagnosed at a localized stage. The 5-year overall survival and disease-specific survival rates were 59% [95% confidence interval (CI) 53–65] and 94% (95% CI 91–98), respectively. In the observation cohort, the number of SCCs was significantly higher than expected as the SIR was calculated to be 33·7 (P < 0·001). Conclusions: Increasing incidence warrants awareness and early diagnosis of CACs. Increased SCC incidence among patients with these tumours highlights the relevance of careful skin examination and follow-up.