Background. Cutaneous melanoma in situ (CMIS) is a nosologic entity surrounded by health concerns and unsolved debates. We aimed to shed some light on CMIS by means of a large population-based study.
Methods. Patients with histologic diagnosis of CMIS were identified from the Surveillance Epidemiology End Results (SEER) database.Results. The records of 93,863 cases of CMIS were available for analysis. CMIS incidence has been steadily increasing over the past 3 decades at a rate higher than any other in situ or invasive tumor, including invasive skin melanoma (annual percentage change [APC]: 9.5% versus 3.6%, respectively). Despite its noninvasive nature, CMIS is treated with excision margins wider than 1 cm in more than one third of cases. CMIS is associated with an increased risk of invasive melanoma (standardized incidence ratio [SIR]: 8.08; 95% confi-