Detection of chromosome aberrations in paraffin sections of seven gonadal yolk sac tumors of childhood.

Yolk sac tumors are the most frequent kind of malignant pediatric germ cell tumor and may have a fundamentally different pathogenesis than adult germ cell tumors. Since few cytogenetic studies have been performed so far, in situ hybridization was applied to interphase cell nuclei of seven gonadal yolk sac tumors of childhood in routine paraffin-embedded tissue sections. The panel of chromosome-specific DNA probes was selected on the basis of their relevance in adult germ cell tumors and consisted of five DNA probes specific for the (peri)centromeric regions of chromosomes 1, 8, 12, 17 and/or X and/or one DNA probe specific for the subtelomeric region of chromosome 1 (p36.3). As in adult germ cell tumors, all pediatric gonadal yolk sac tumors had an increased incidence of numerical chromosome aberrations. All tumors showed an overrepresentation of at least three chromosomes. Gains of chromosome 12, which is highly specific in adult germ cell tumors, were diagnosed in six pediatric gonadal yolk sac tumors. The DNA indices determined in the paraffin-embedded tumor material correlated well with the in situ hybridization findings. A chromosome was either over- or underrepresented, compared with the corresponding DNA indices, in only a few cases. The short arm of chromosome 1 in adult germ cell tumors is often involved in structural aberrations. In pediatric germ cell tumors, the short arm of chromosome 1 is also a nonrandom site of structural aberrations. Moreover, the presence of a deletion at 1p36.3 in four out of five tumors suggests that the loss of gene(s) in this region is an important event in the pathogenesis of gonadal yolk sac tumors of childhood.