PRIMARY MEDIASTINAL SEMINOMA FOUND ON EVALUATION FOR WEIGHT LOSS

Abstract

SESSION TITLE: Medical Student/Resident Disorders of the Mediastinum Posters SESSION TYPE: Med Student/Res Case Rep Postr PRESENTED ON: October 18-21, 2020 INTRODUCTION: Extragonadal germ cell tumors (GCTs) typically arise in midline locations such as mediastinum and retroperitoneum. They are formed either due to failure of primordial germ cells to migrate to the gonadal ridges [1] or reverse migration of the transformed germ cells in the testes [2]. Mediastinal seminomas are rare tumors constituting about 1/3rd of malignant mediastinal GCTs and 2-4 percent of mediastinal masses [3]. CASE PRESENTATION: A 55-year-old man with a history of active smoking (½ pack cigarettes per day), hepatitis C, bipolar disorder, prior alcohol/intravenous drug use (heroin and cocaine) presented with shortness of breath and 50-pound weight loss. Chest computed tomography (CT) revealed a 3.0 x 1.1 cm para-aortic lymph node. Positron emission tomography (PET/CT) scan showed hypermetabolic activity (maximum standardized uptake value of 10). Bronchoscopy with EBUS (endoscopic ultrasound) and mediastinoscopy were considered as methods to obtain tissue but discarded due to the location of the mass. He underwent a left Video-assisted thoracoscopic surgery (VATS) which showed seminoma. H&E (hematoxylin and eosin) slides revealed pale tumor cells with distinct nuclei and prominent central nucleoli in a background of lymphocytic infiltrate. The tumor cells stained positive for germ cell markers CD117, Oct 3/4 and Sall 4; but were negative for melanoma markers (Mart1a, S100), as well as CK20, CK7, Pancytokeratin, CD30, CD15, TTF1 and CDX2. DISCUSSION: Mediastinal seminomas occur mainly in men aged 20 to 40 years. They are typically slow growing and can be very bulky by the time they cause symptoms. Serum beta subunit of human chorionic gonadotropin (beta-hCG) is elevated in approximately one-third of patients. They do not produce alpha-fetoprotein (AFP). Ultrasound is advised in all cases to evaluate for any testicular primary. Seminomas are exquisitely sensitive to both cisplatin-based chemotherapy and radiotherapy (RT) but local control with surgery and RT only have modest success due to their typically later presentation. The commonly used chemotherapy regimens are 3 cycles of bleomycin/etoposide/cisplatin (BEP) or 4 cycles of etoposide/cisplatin (EP) (in patients who have previously received RT, who have underlying lung disease or age more than 50 years to avoid bleomycin lung toxicity). Long-term disease-free survival is achieved in roughly 90 percent of patients treated with chemotherapy. CONCLUSIONS: Primary mediastinal seminoma is a malignant extragonadal GCT most commonly found in the anterior mediastinum. Usually, young men in their 20-40s present with large 4-11cm anterior mediastinal masses which cause symptoms by compressing local structures. Or, as in our case, they are found incidentally. Surgery/RT can be considered but many patients present late so local control is not possible. However, these tumors respond well to chemotherapy with complete response rates of 90% Reference #1: Intracranial germ cell tumors: a comprehensive review of proposed embryologic derivation; Glenn OA, Barkovich AJ; Pediatr Neurosurg. 1996;24(5):242; PMID 8933567 Reference #2: Genetics and biology of adult human male germ cell tumors; Chaganti RS, Houldsworth J; Cancer Res. 2000;60(6):1475; PMID 10749107 Reference #3: Primary germ cell tumors of the mediastinum: II. Mediastinal seminomas--a clinicopathologic and immunohistochemical study of 120 cases; Moran CA, Suster S, Przygodzki RM, Koss MN; Cancer. 1997;80(4):691; PMID 9264352 DISCLOSURES: No relevant relationships by William Han, source=Web Response No relevant relationships by Sahib Singh, source=Web Response