Untying the Gordian knot of composite hemangioendothelioma: Discovery of novel fusions

Vascular tumors of intermediate malignancy: An update

The term "hemangioendothelioma" is used for endothelial neoplasms of intermediate malignancy and describes a group of rare neoplasms having biologic behavior falling in between that of the benign hemangiomas and fully malignant angiosarcomas. The hemangioendotheliomas fall into several specific, clinicopathologically and genetically distinct entities, specifically epithelioid hemangioendothelioma, kaposiform hemangioendothelioma, papillary intralymphatic angioendothelioma and retiform hemangioendothelioma (hobnailed hemangioendothelioma), pseudomyogenic hemangioendothelioma, composite hemangioendothelioma, and YAP1::TFE3-fused hemangioendothelioma. The clinical, morphologic, immunohistochemical, and genetic features, and the differential diagnosis of each of these rare entities are discussed in this review.

Dural composite hemangioendothelioma: The first intracranial case

Background

Composite hemangioendothelioma (CHE) is a rare, locally aggressive neoplasm of intermediate malignant potential. It is composed of a mixture of vascular tumors with a predilection for the dermis and subcutis of the extremities.

Case Description

In this report, we describe a 41-year-old man who presented with a 2-month history of headache, dizziness, and intermittent seizures. Magnetic resonance imaging showed a hemorrhagic, multilobulated, and dural-based mass with extension into the calvarium. The mass measured 10.3 × 4.8 × 4 cm along the interhemispheric fissure and encased the superior sagittal sinus. Excision was performed, and histopathologic examination revealed a heterogeneous mixture of vascular components consisting of epithelioid hemangioendothelioma, retiform hemangioendothelioma, and hemangioma. This is the first report of a primary intracranial CHE.

Conclusion

The spectrum of mesenchymal neoplasms within the cranium expands to encompass CHE.

A cutaneous epithelioid vascular tumor harboring a TPM3::ALK fusion

Substantial progress has been made in understanding the molecular pathways associated with vascular tumors over the last two decades. In addition to mutations and copy number aberrations, fusions have emerged as significant contributors to the pathogenesis of a notable subset of vascular tumors. In this report, we present a case of an unusual intradermal vascular tumor with epithelioid cytomorphology. Immunohistochemistry revealed diffuse positivity for CD31, ERG and Factor VIII, supporting its endothelial lineage. RNA sequencing (ArcherFusion Plex) revealed the presence of an in-frame fusion between the genes TPM3 Exon 8 and ALK Exon 20. Immunohistochemistry confirmed ALK expression by the endothelial cells. To our knowledge, this is the first documented case of a vascular tumor harboring an ALK fusion. It may fall within the spectrum of epithelioid hemangiomas; nevertheless, we cannot definitively exclude the possibility of it being a distinct and potentially unique benign entity on its own.