Emerging Pediatric Cutaneous Epithelioid Vascular Tumor with TPM4::ALK fusion

Summary: An 11-year-old boy presented with an enlarging, bleeding lesion over his back for several months. Clinically, a pyogenic granuloma was suspected. Histopathology showed a dermal based neoplasm composed of cells arranged in cords with poorly formed vascular slit like channels, an epidermal collarette and overlying ulceration. Lesional cells had abundant pale amphophilic cytoplasm, moderately enlarged nuclei with vesicular chromatin and small nucleoli. Mitotic activity was not conspicuous. Immunohistochemistry showed diffuse ALK D5F3 positivity in the epithelioid vascular cells. CD34 and ERG stains colocalized with the ALK positive cells, supporting an endothelial lineage. SOX10 and p63 were negative. Next generation sequencing revealed a TPM4::ALK fusion. The immunohistochemical and molecular studies supported a diagnosis of an ALK rearranged epithelioid vascular tumor. This is a newly described entity thought to be in the spectrum of benign epithelioid hemangiomas. This represents the second reported case in the literature. The patient underwent a conservative re-excision. Only limited clinical follow-up is available to date. Due to the emergence, and rarity of this entity, it may not enter the differential for a solitary epithelioid vascular neoplasm. We present this case to raise awareness of this entity to avoid misdiagnosis and to highlight its histopathologic features and immunophenotype.