INTRAOSSEOUS EPITHELIOID HAEMANGIOENDOTHELIOMA OF THE MANDIBLE

Case A fit and well 25-year-old man presented with worsening pain and bony swelling on the lingual aspect of the right premolar region. Radiology showed a multiloculated radiolucent lesion of the anterior mandible with bone expansion and displacement of roots. Initial biopsy revealed fragments of nested epithelioid tumor within the marrow space with extravasated red blood cells and hemosiderin suggestive of vascular origin. Further biopsy showed histologic features of epithelioid haemangioendothelioma (eHAE). Samples were sent to the National Orthopaedic Hospital for molecular testing but this was inconclusive, likely owing to formic acid decalcification. MDT decision for surgical resection was carried out with primary reconstruction. Histology from the resection revealed complete excision of eHAE with focal erosion through the buccal cortex. The patient has recovered well, and to date there is no evidence of recurrence. Discussion eHAE is a very rare vascular tumor of low-grade malignancy, which presents within the lung, liver, or bone including of the head and neck region with 4 cases reported within the mandible. Despite characteristic morphology, diagnosis can be challenging because of small sample size and the rarity of diagnosis. eHAEs are characterized by a WWTR1-CAMTA1 fusion with a minority also showing a YAP1-TFE3 fusion, however decalcification in formic acid can prevent adequate molecular analysis. Conclusions eHAE is a rare tumor with characteristic histologic features and potential for recurrence and metastasis. Molecular testing can assist diagnosis, and development of local tissue pathways for intraosseous tumors that facilitate molecular testing is essential for prompt diagnosis.