Atypical vascular neoplasm with TFE3 immunohistochemical expression, suggestive of epithelioid hemangioendothelioma

Abstract

Epithelioid hemangioendothelioma (EHE) is a rare tumor of the head and neck region which was first described by Weiss and Enziger in 1982. It was considered an intermediate malignant potential tumor but currently, the WHO classifies it as a malignant neoplasm. The common molecular driver of the neoplasm is a gene fusion of WWTR1::CAMTA1. However, a much less common subset of cases display YAP1::TFE3 gene fusion. Clinically, the lesion presents as a slow-growing mass with a tendency for regional lymph node metastasis. Histopathology for EHE can share features with other vascular lesions both benign and malignant lesions ranging from epithelioid hemangioma to epithelioid angiosarcoma. Immunohistochemical markers are not always helpful when determining vascular lesions from each other. Vascular lesions stain positive with CD31, and ERG which is helpful in distinguishing this tumor from other epithelioid morphology neoplasms. This case presents a 42-year-old male with a 4-month history of right buccal mucosa swelling. The lesion was thought to be excised at original biopsy but in approximately 2 weeks recurred with rapid growth. The biopsy showed a vascular lesion with an epithelioid morphology, cellular pleomorphism, increased mitoses, endothelial hyperplasia, and an infiltrate of eosinophils. A confounding morphology with a concerning rapid growth rate. IHC testing was positive for CD31, ERG, and TFE3 suggesting an epithelioid hemangioendothelioma but molecular tests are still pending as of the writing of this abstract.