Superficial (Cutaneous) Tumors Exhibiting Morphological and Phenotypic Differentiation Toward Smooth Muscle and Pericytic Lineages

Diagnosing low-grade spindle cell lesions of the skin can be challenging. In particular, distinguishing among fibroblastic, myofibroblastic, and smooth muscle or pericytic proliferations may be difficult during a routine histologic examination. This article provides an update on recent developments in superficial mesenchymal tumors exhibiting smooth muscle and pericytic differentiation. We focus on the characterization of clinicopathological features, differential diagnosis, and recurrent molecular alterations. Additionally, we address superficial leiomyosarcomas, which are now classified as atypical intradermal smooth muscle neoplasms due to their low risk of aggressive behavior. The article also discusses Epstein-Barr virus-associated smooth muscle tumors.