Chromosomal abnormalities of a mediastinal embryonal cell carcinoma in a patient with 47,XXY Klinefelter syndrome: evidence for the premeiotic origin of a germ cell tumor.

Trypsin-Giemsa banding studies were performed on 30 tumor cells from an embryonal cell carcinoma originating in the mediastinum of an 18-year-old male with the Klinefelter syndrome (47,XXY). All tumor cells revealed an XXY chromosomal pattern with the addition of extra chromosomes. Electrophoretic patterns of the patient's red blood cells and tumor cells were identical. These data suggest that this germ cell tumor originated from a primordial germ cell in which oncogenesis had occurred prior to meiotic division.