Epithelioid Haemangioma & Haemangioendothelioma of Bone

Multiple lytic bone lesions clustered in one limb with an epithelioid vascular tumour on biopsy point to the spectrum of epithelioid vascular tumours of bone, and the multifocality is characteristic. I would think of this as a spectrum of increasing aggressiveness: the benign, locally aggressive epithelioid haemangioma; the intermediate-grade epithelioid haemangioendothelioma, or EHE; and the high-grade malignant angiosarcoma. So my first task is to grade the lesion accurately, because that determines management and prognosis. I would confirm the endothelial origin with vascular immunomarkers such as CD31, ERG and FLI1, and look for the molecular signature of EHE, the WWTR1-CAMTA1 fusion, reflected in nuclear CAMTA1 staining, with a YAP1-TFE3 variant in a minority. I would also exclude metastatic carcinoma, which the epithelioid morphology can mimic, and crucially exclude angiosarcoma at the malignant end. The multifocal pattern can be mistaken for metastatic disease, so I would correlate with imaging including the extent and any visceral involvement, since EHE characteristically occurs in bone, soft tissue, liver and lung. Management is by grade and extent: a benign epithelioid haemangioma is treated by curettage or excision with low recurrence; EHE is treated by wide resection where resectable, with systemic therapy and multidisciplinary management and surveillance for multifocal or metastatic disease given its variable behaviour; and angiosarcoma needs aggressive multimodality treatment. All of this is best coordinated through a specialist sarcoma centre, with a properly planned biopsy before any definitive surgery.