18473 Pseudomyogenic hemangioendothelioma: An aggressive case of a rare vascular tumor

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A 19-year-old otherwise healthy man presented with new painful necrotic lesions on the left fifth toe and heel for four months. Symptoms began months after stepping on a foreign object and progressed rapidly despite multiple antibiotic courses. Imaging showed indeterminate findings of osteomyelitis. Noninvasive vascular studies revealed mild peroneal artery insufficiency. The patient started Aspirin and daily wound care without relief. He was then referred to Dermatology and biopsies were obtained. Histologic sections from both lesions showed a dense dermal proliferation of epitheliod to spindled cells with admixed neutrophils and eosinophils. Several immunohistochemical stains were performed: AE1/AE3(+), ERG(+), HHV8(−), Melan A(−), SOX-10(−), INI-1 (retained). Laboratory work-up was unremarkable including CBC, CMP, ESR, CRP, PT, PTT, ANA, ANCA, urinalysis, and blood cultures. The diagnosis of pseudomyogenic hemangioendothelioma was made and staging was initiated. Imaging revealed multiple tumor foci in the left metatarsal, tibia, groin, and lungs. Treatment consisted of toe amputation, wide local excision of the heel, and systemic everolimus. Pseudomyogenic hemangioendotheliomas are rare vascular tumors of intermediate malignant potential which classically present as multifocal painful nodules on the lower extremities of young males. While concurrent bone involvement can be seen in 20% of cases, distant metastases are exceedingly rare. Treatment is predominately surgical though recent detection of SERPINE1-FOSB gene fusions has prompted the use of mTOR inhibitors in unresectable tumors given their shared signaling pathways. This case represents an aggressive presentation of pseudomyogenic hemangioendothelioma with novel use of mTOR inhibitors as treatment.