Background

After chemotherapy, a small subset of mediastinal non-seminomatous germ cell tumors evolves into growing benign teratoma masses despite normalized tumor markers. This condition is termed the growing teratoma syndrome. We present a case of a massive mediastinal mature teratoma requiring cardiopulmonary bypass and complete vascular graft reconstruction of the superior vena cava and innominate vein confluence.

Case presentation

A 31-year-old man presented to the emergency department with acute right-sided chest pain, dyspnea, and weight loss. Imaging revealed a 16.7 cm anterior mediastinal mass compressing the superior vena cava, with elevated alpha-fetoprotein and beta-human chorionic gonadotropin levels. Biopsy results revealed mature teratoma. After three cycles of platinum-based chemotherapy, tumor markers normalized, but the mass enlarged to 22 cm. He then underwent clamshell thoracosternotomy with cardiopulmonary bypass, mediastinal mass complete en bloc resection, lung sparing, and venous graft reconstruction of the superior vena cava. Final pathology confirmed mature teratoma with negative margins. 

Conclusions

This case highlights the importance of recognizing growing teratoma syndrome in patients with an enlarging mediastinal mass despite normalized tumor markers following chemotherapy for presumed non-seminomatous germ cell tumor. Complete surgical resection remains the only curative treatment, though it is highly technically challenging. Early surgical referral and multidisciplinary planning are essential for optimal outcomes in such high-risk cases.