Clinicopathologic and molecular features of vascular tumors in a series of 118 cases

Vascular tumors are composed of benign, intermediate, and malignant lesions. The diagnosis is challenging because some entities demonstrate overlapping morphologies and harbor the same genetic alterations. We describe herein a cohort of vascular tumors with clinicopathologic, immunohistochemical, and molecular features.

118 vascular tumors including 56 angiosarcomas, 18 epithelioid haemangioendotheliomas (EHE), 25 epithelioid haemangiomas (EH), 8 pseudomyogenic haemangioendotheliomas (PHE), 1 papillary intralymphatic angioendothelioma (PILA), 2 kaposiform haemangioendotheliomas (KHE), 3 Kaposi sarcomas, 2 retiform haemangioendotheliomas (RHE), and 3 anastomosing haemangiomas were assessed. FOSB, c-Fos, CAMTA1, and TFE3 expression and gene rearrangements were analyzed by immunohistochemical staining and FISH, respectively. Our results showed that FOSB expression was diffusely positive in all 8 PHEs, focally or sparsely in 12 EHs, and in 2 angiosarcomas. C-FOS expression was sparsely to diffusely positive in 15 EHs, focally or sparsely in 17 angiosarcomas, 1 EHE, 1 Kaposi sarcoma, and 1 PHE. CAMTA1 expression was positive in only 12 EHEs. TFE3 expression was focally or sparsely positive in all 8 PHEs, 22 angiosarcomas, 6 EHEs, 3 EHs, 2 Kaposi sarcomas, and 2 AHs. FOSB rearrangement was found in 5 PHEs, FOS rearrangement only in 1 EH, CAMTA1 rearrangement in 4 EHEs.

FOSB and CAMTA1 are useful diagnostic markers for PHE and EHE, respectively. FOSB and FOS fusion represent a subset of epithelioid haemangioma. TFE3 is not a diagnostically meaningful marker in a majority of vascular tumors. The combined utility of these markers will facilitate the differential diagnosis in vascular tumors with morphologic overlap.