DefinitionMalignant teratoma is a type of cancer made of cysts that contain one or more of the three main types of cells found in a developing baby (embryo). These cells are callled ectoderms, mesoderms, and endoderms.Alternative NamesDermoid cyst - malignant; Nonseminomatous germ cell tumor - teratoma; Immature teratomaCauses, incidence, and risk factorsMalignant teratoma occurs most often in young men in their 20s - 30s. It is often located in the chest area. Most malignant teratomas can spread throughout the body, and have spread by the time of diagnosis.A number of other cancers are often associated with these tumors, including:Acute myelogenous leukemia (AML)Embryonal rhabdomyosarcomaMalignant histiocytosisMyelodysplasia (MDS)Small cell undifferentiated carcinomaSymptomsSymptoms inclu