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Case Reports

Abstract

Vascular neoplasms comprise a heterogenous group of tumors ranging from benign to malignant and have been increasingly linked to gene fusions. This report presents a rare cutaneous epithelioid vascular tumor in a 42-year-old female, characterized by a novel TPM3/4::ALK gene fusion. Histologically, the lesion was a well-circumscribed, dome-shaped dermal tumor composed of epithelioid endothelial cells with mild cytologic atypic, abundant eosinophilic cytoplasm, and a sparse inflammatory infiltrate. Positive ERG immunohistochemistry staining confirmed vascular differentiation. ALK-1 was diffusely positive. TPM3/4::ALK gene fusion was detected via molecular analysis, highlighting ALK as the likely oncogenic driver in this tumor. The morphology resembled epithelioid hemangioma, a benign vascular tumor known to harbor FOS gene rearrangements, although the ALK fusion suggests a distinct pathogenesis. This case represents the second known instance of a cutaneous epithelioid vascular tumor with a TPM3::ALK fusion, expanding the molecular spectrum of ALK-rearranged vascular tumors, and suggesting a possible novel diagnostic entity. Given ALK’s role as a therapeutic target, recognition of such fusions is clinically significant. Further studies are needed to clarify the clinical behavior and classification of these tumors within the spectrum of fusion-driven vascular neoplasms.