Résumé
Cutaneous leiomyosarcoma (cLMS) is a superficial smooth-muscle type of sarcoma. It is an uncommon skin neoplasm for whose data are missing, especially concerning the outcomes of patients and the molecular profile of cLMS. Objectives: to describe clinicopathological features, therapeutic strategies, long-term outcomes of primary cLMS and to explore their molecular profile.Methods: a retrospective multicentric study of patients with cLMS referred to four French Dermatology Departments, from January 2000 to June 2019 was conducted. Demographics data, clinical-histopathological features and outcomes of patients were collected. Kaplan-Meier method was used to evaluate the survival rates. Comprehensive molecular profiling using CGH/SNP-array, targeted NGS and RNA sequencing was performed. Results: seventy-nine cases of primary cLMS were included; 57 (72%) were male; median age at diagnosis was 70.0 years (interquartile range [IQR], 57-79). Median duration of follow-up was 39 months (IQR, 4.9-73.9). cLMS mostly occurred in the lower limbs (36.7%), as a painless nodule (62%). More than two-thirds (62%) of cLMS were low-grade sarcomas (grade I according to the FNCLCC classification). Patients who no experienced local recurrence neither distant metastasis had a mean margin larger than those who experienced a recurrence or metastasis (1.80 vs 1.06 cm, p= 0.03). The estimated 24-month OS and PFS rates were 92% and 77% respectively. Seven cases of cLMS metastasized, the estimated 24-month RFS rate was 93%, it decreased to 90% at 5 years. Fourteen cases were molecularly investigated. Using CGH/SNP-array, we observed three different types of quantitative genomic profiles: four cases showed no quantitative anomaly; three cases, few quantitative genomic anomalies and four cases a complex genomic profile with more than 10 quantitative anomalies. Targeted NGS detected two cases with missense mutations of TP53. Most commonly altered genes are RB1 (5 cases), TP53 (5 cases) and MYOCD (2 cases).Conclusions: most of the time prognosis of cLMS is good with an excellent outcome after a 1 cm resection margins. Nevertheless, some cLMS, especially those treated with limited margins and those with histological pejorative factors may metastasize, suggesting that a wider local excision and long-term follow-up are needed. We identified a molecular aggressive subgroup of cLMS. Whether this subgroup evolve differently, need to be explored in a larger, prospective cohort.