Cutaneous Leiomyosarcoma of the Skin: An Updated Review of Epidemiology, Pathogenesis, and Management

Primary cutaneous leiomyosarcoma (LMS) is a rare smooth muscle neoplasm encompassing a spectrum of dermal and subcutaneous tumors with distinct clinical behaviors. Dermal LMS typically presents as a small, firm nodule arising from arrector pili muscle and generally follows an indolent course, whereas subcutaneous LMS originates from vascular smooth muscle and demonstrates greater infiltrative potential, larger size at presentation, and a substantially higher risk of recurrence, metastasis, and disease-specific death. Histologically, LMS is characterized by intersecting fascicles of spindle cells with smooth muscle differentiation, with the diagnosis being confirmed by smooth muscle actin and desmin immunoreactivity. Recent molecular profiling has identified tumor suppressor pathway dysregulation-particularly TP53 and RB1 loss-and widespread copy-number instability as central drivers of cutaneous LMS. Clinically, outcomes are governed principally by depth, grade, and margin status: dermal, low-grade tumors rarely metastasize, whereas lesions with higher-grade or subcutaneous extension account for most adverse events. Complete surgical excision with negative margins remains the cornerstone of therapy, with Mohs micrographic surgery offering precise margin control for select superficial tumors. Ongoing debate regarding the atypical intradermal smooth muscle neoplasm (AISMN) designation for dermally-confined tumors reflects evolving understanding, although we argue that risk stratification is best guided by histologic features rather than nomenclature alone.