TPM4::ALK Rearranged Cutaneous Epithelioid Vascular Tumor: A Case Report.

Epithelioid vascular tumors range from benign to malignant, including epithelioid hemangioma, cutaneous epithelioid angiomatous nodule, epithelioid hemangioendothelioma, and epithelioid angiosarcoma. Vascular tumors with epithelioid morphology and TPM3/4::ALK fusions have recently been added to this list, in a cohort of five cases. Herein, we report the sixth case (second case with TPM4::ALK specifically). Consistent with the previous report, the current case occurred in a young boy (lateral upper back, 11 years old) and demonstrated a circumscribed tumor with an epidermal collarette, peripheral ectatic thin vessels, and variably solid to vasoformative epithelioid cells with small, somewhat crescent-shaped vascular channels. CD34, ERG, and ALK immunohistochemical stains were positive and further highlighted vascular structures. RNA sequencing revealed an in-frame fusion between TPM4 Exon 8 and ALK Exon 20. Conservative excision was performed and recurrence has not been observed at one-year follow-up.