Growing teratoma syndrome in an adolescent with a testicular germ cell tumor: a case report

Growing teratoma syndrome (GTS) is a condition characterized by a paradoxical increase in tumor size during or after chemotherapy and/or surgical treatment for germ cell tumors. Due to its relative rarity, GTS may be misinterpreted as disease progression. However, a decrease in tumor markers (alpha-fetoprotein (AFP) and human chorionic gonadotropin (hCG)) in the blood, a paradoxical increase in tumor size during chemotherapy, and a verified histological diagnosis of mature teratoma after the tumor removal confirm GTS. Here we report a clinical case of a patient in whom we observed a decrease in tumor markers (AFP and hCG) in the blood during treatment, a paradoxical increase in the tumor size and normal AFP and hCG levels 5 months after the end of chemotherapy and a histologically verified diagnosis. These clinical features are consistent with the diagnostic criteria of GTS. The patient's parents gave consent to the use of their child's data, including photographs, for research purposes and in publications.