Mediastinal Teratoma with Angiosarcomatous Overgrowth in a Background of Vasculogenic Mesenchymal Tumor

Abstract Introduction/Objective Vasculogenic mesenchymal tumor refers to neoplastic reiteration of embryonic vasculogenesis. It is most commonly associated with nonseminomatous germ cell tumors of the mediastinum, in particular yolk sac tumor. In rare instances these lesions progress to angiosarcoma. Herein, we describe a case of angiosarcoma in a background of vasculogenic mesenchymal tumor in the setting of a mediastinal teratoma. Methods/Case Report A 33-year-old male, with a past medical history of anxiety, and right orchiectomy for testicular torsion, presented with shortness of breath, chest pain, and left arm swelling. Imaging studies demonstrated a mediastinal mass. Biopsy of the mass showed a germ cell tumor most compatible with a teratoma in the limited specimen. The patient received two rounds of chemotherapy and additional treatments were discontinued due to poor tolerance. Subsequent imaging showed continued increase in the size along with mass effect causing moderate to severe compression of the superior vena cava. Subsequently, the patient underwent resection of the mass. Grossly the mass was predominantly encapsulated with areas of capsular disruption. Sectioning revealed heterogeneous cut surfaces with fleshy, cystic, and necrotic areas. Morphologically the tumor was composed predominantly of teratomatous elements with areas of anastomosing atypical vascular channels within a hypocellular stroma suggestive of vascular genic mesenchymal as well as areas reminiscent of Masson lesion. Focally within these areas were malignant spindle cell proliferations compatible with angiosarcoma. The patient had an elevated AFP; however, no yolk sac tumor component was identified after thorough sampling. Final diagnosis of teratoma with angiosarcoma in a background of vasculogenic mesenchymal tumor was rendered after expert consultation. Results (if a Case Study enter NA) NA Conclusion Somatic-type malignancy and sarcomatous overgrowth are known to occur in mediastinal germ cell tumors; however, classification of the sarcomatous overgrowth can be challenging. Vasculogenic mesenchymal tumor is an exceedingly rare sarcomatous overgrowth that can rarely progress to angiosarcoma.