Clonal relationship between the teratoma and rhabdomyosarcoma of the germ cell tumor was established by the presence in both of i(12p), the characteristic marker of germ cell tumors.
This included a germ cell tumor in 12 (30%) patients by the finding of i(12p), increased 12p copy number, or a deletion of the long arm of chromosome 12.
One or more copies of i(12p), excess 12p copy number, or a deletion on the long arm of chromosome 12 was found in seven of 28 (25%) midline tumors of uncertain histogenesis, thus establishing a diagnosis of a germ cell tumor in these patients.