RESUMEN
Testicular mixed germ cell tumors (TMGCTs) are aggressive neoplasms that often have metastases at the time of diagnosis, primarily in the lungs, bones, and brain. Gastrointestinal metastases are rare, occurring in less than 5% of cases, while duodenal involvement is extremely rare, with only few reported cases. Furthermore, gastrointestinal bleeding is an atypical initial presentation of metastatic TMGCTs. Herein, we present a very rare case of upper gastrointestinal bleeding caused by a duodenal metastasis of a TMGCT in a 24-year-old man. The patient was admitted to our hospital due to abdominal pain and melena with a hemoglobin level of 52 g/L. He had no history of testicular swelling, or any other symptoms or signs of a testicular tumor. Upper gastrointestinal endoscopy revealed a duodenal tumor mass with irregular bleeding, and abdominal ultrasound and computed tomography showed a duodenal mass that infiltrate retroperitoneum. Emergency surgery was performed, and the histopathological findings of the resected specimen were consistent with TMGCT metastasis. Subsequently, a testicular tumor was confirmed and surgically removed; however, multiple metastatic deposits were observed in the lungs. Due to the patient's poor general condition, chemotherapy was not performed. The patient died 3 months after the initial diagnosis. This case suggests that, although duodenal metastatic TMGCTs are rare, they should be considered in the differential diagnosis of gastrointestinal bleeding in young male patients.