Definition

A type of tumor that begins in germ cells (cells that form sperm or eggs). Nongerminomas can occur in the ovaries or testicles or other parts of the body, but they occur most often in the central nervous system (brain and spinal cord). This happens when a germ cell travels to the brain during fetal development and later becomes a germ cell tumor. There are several types of nongerminoma tumors, including embryonal carcinoma, yolk sac tumor, choriocarcinoma, teratoma, and mixed germ cell tumor. Most nongerminomas make hormones, such as alpha-fetoprotein (AFP) and beta-human chorionic gonadotropin (beta-hCG). Nongerminomas are usually malignant (cancer) and tend to grow and spread quickly. They usually occur in children.