Primitive neuroectodermal tumor arising from an untreated congenital undescended testicle.

A 26-year-old male with a personal history of schizophrenia initially presented with a 13 cm pelvic mass corresponding to a cryptorchidic testis. The patient was treated with primary and second-line chemotherapy for metastatic germ-cell tumor followed by surgical consolidation. Final pathology revealed a primitive neuroectodermal tumor (PNET) mixed with mature teratoma. Despite multidisciplinary management, significant patient non-compliance led to inadequate follow up and treatment delays ultimately resulting in death. To our knowledge, this is the only reported case of teratoma with malignant transformation arising from an untreated congenital undescended testicle.