Primary cutaneous melanoma features predict development of in-transit metastases/satellite lesions: Mayo Clinic experience, 2010 to 2014

To the Editor: In-transit metastases (ITM) and satellite lesions (S) are not captured in national registries. We performed a high-powered case-control study of the clinicopathologic characteristics of primary cutaneous melanoma (PCM) to identify microscopic features associated with subsequent development of ITM/S. After reviewing medical records of patients with ITM/S diagnosed from January 1, 2010, through December 31, 2014, at Mayo Clinic, Rochester, we then studied all patients (n = 27) who were at least 18 years old at the time of PCM diagnosis and later developed ITM/S without synchronous stage IV disease. Patients were followed through June 2017. A control cohort of patients with PCM without ITM/S, matched 3:1 for age and the median follow-up period, was identified. PCM histopathology from all patients was re-reviewed by a dermatopathologist. Univariate models were used to explore the association between age, anatomic location of the PCM, melanoma subtype, Breslow depth (BD), ulceration, angiolymphatic invasion, number of mitosis, and development of ITM/S. For multivariate analysis, BD was retained.