Spontaneous regression as a 'burned-out' non-seminomatous testicular germ cell tumor: a case report and literature review.

Testicular germ cell tumors (TGCTs) are the most frequent type of cancer in young adults. An exceptional event is the spontaneous regression (SR) of the primary tumor. Herein, we describe a burned-out non-seminomatous TGCT case and relevant literature review. A 34-year-old male presenting with low back pain was found to have a retroperitoneal mass upon urotomography. During workup, a heterogeneous testicular mass was evident, and its biopsy showed findings that support the diagnosis of spontaneous tumoral regression. The patient underwent unilateral orchiectomy and a chemotherapy protocol was later initiated, with 85% regression of the retroperitoneal metastatic mass. No progression of the primary tumor has been found. The etiology of SR across different cancer types appears to be associated with the host's immune response and an angiogenic disturbance of the tumor microenvironment. The burned-out phenomenon is a rare event that needs further research into its molecular sequencing.