Isochromosome 12p-positive pineal germ cell tumor.

We report the chromosomal characteristics of a recurrent pineal non-seminomatous germ cell tumor in a 16-year-old male patient. This non-seminomatous tumor had the following components: embryonal carcinoma, teratoma, yolk sac tumor, and trophoblastic giant cells. Chromosome analysis showed a near-triploid karyotype (64 chromosomes), including two copies of an isochromosome 12p. This latter finding could be confirmed using 12p-specific competitive in situ hybridization techniques applied to cultured cells (T2219-P6 cell line) derived from the tumor. The present findings are in keeping with the hypothesis that isochromosome 12p formation is associated with the development of malignant extragonadal germ cell tumors.