From pure testicular Teratoma to primitive neuroectodermal tumor: Successful management of Teratoma malignant transformation with widespread metastases in a young adult.

Midline retroperitoneal masses in young males often present a diagnostic challenge, with metastases from testicular origins being a primary consideration. Beyond the initial pathology of testicular cancer, these masses can undergo transformation, including the development of teratomas. This report describes an unusual case of a calcified retroperitoneal mass originating from a testicular pure teratoma that underwent a rare transformation into a Primitive Neuroectodermal Tumor (PNET), comprising approximately 85 % of the tumor volume. The patient's successful treatment involved a comprehensive approach combining surgical resection and chemotherapy.