An extragonadal non-seminomatous malignant germ cell tumor that arises from the mediastinum and is associated with a hematologic malignancy. The hematologic malignancies are clonally related to the malignant germ cell tumor and include acute leukemias, myelodysplastic syndromes, myeloproliferative neoplasms, and mastocytosis. [from
NCI]