ISOCHROMOSOME 12P-POSITIVE PINEAL GERM-CELL TUMOR

We report the chromosomal characteristics of a recurrent pineal nonsem inomatous germ cell tumor in a 16 year-old male patient. This nonsemin omatous tumor had the following components: embryonal carcinoma, terat oma, yolk sac tumor, and trophoblastic giant cells. Chromosome analysi s showed a near-triploid karyotype (64 chromosomes), including two cop ies of an isochromosome 12p. This latter finding could be confirmed us ing 12p-specific competitive in situ hybridization techniques applied to cultured cells (T2219-P6 cell line) derived from the tumor. The pre sent findings are in keeping with the hypothesis that isochromosome 12 p formation is associated with the development of malignant extragonad al germ cell tumors.