Cutaneous Hemangioma With Epithelioid Features Harboring a TPM4::ALK Fusion

Vascular neoplasms comprise a heterogeneous group of tumors ranging from benign to malignant, increasingly defined by recurrent gene fusions. In this report we describe a cutaneous hemangioma with epithelioid features harboring a TPM4::ALK gene fusion in a 43-year-old female. On histology, this dermal-based lesion was composed of epithelioid endothelial cells with no overt cytologic atypia and abundant cytoplasm. Immunohistochemistry showed the epithelioid cells were positive for ERG and showed diffuse intracytoplasmic ALK-1 expression. The fusion was detected via RNA sequencing, highlighting ALK as a potential oncogenic driver in this tumor. The morphology resembled epithelioid hemangioma, a benign vascular tumor known to harbor FOS gene rearrangements. This case represents the second known instance of a cutaneous hemangioma with epithelioid features and a TPM4::ALK fusion. Additional studies are needed to clarify the biological behavior and classification of these tumors within the spectrum of fusion-driven vascular neoplasms.