A Wolf in Sheep’s Clothing – A Rare Case of an Angiosarcoma Arising from a Schwannoma in the Posterior Mediastinum: A Case Report

Introduction: Schwannoma is one of the benign tumors occurring in the posterior mediastinum. However, angiosarcoma is a malignant tumor of vascular origin and presents as an infiltrating mass. Primary angiosarcoma of the mediastinum is very rare. Few cases have been reported in the atrium, pulmonary vein, and lung and present with chest pain. Angiosarcoma arising from a benign tumor like a schwannoma is very rare; only a handful of cases have been reported in the literature. This case is presented for its rarity and awareness that even a schwannoma presenting as well-circumscribed mediastinal mass can harbor a life-threatening malignancy. Case Report: A 51-year-old male presented with chest pain, and on investigation, there was an extrapulmonary and posterior mediastinal mass in the left paravertebral region with a benign appearance and his serum tumor markers were normal. However, a needle biopsy showed evidence of an angiosarcoma. Hence, with these contradicting results, a surgical exploration was done and since it was well delineated was excised completely. Grossly, it was a well-circumscribed mass measuring 12.5 cm × 9.5 cm × 6.5 cm with a variegated appearance with pale–yellow and hemorrhagic areas. A diagnosis of an epithelioid angiosarcoma arising from a schwannoma was made by light microscopic and immunohistochemical findings. Conclusion: Epithelioid angiosarcoma is a rare malignant transformation occurring in a schwannoma. It can also have a deceptively benign appearance as in our case, and in any symptomatic long-standing posterior mediastinal schwannoma, this differential should be kept in mind when planning surgery and further treatment.