Studies on nuclear DNA content in testicular germ cell tumors using flow cytometry

Flow cytometric DNA analysis was done in 76 patients of testicular germ cell tumors (GCTs) experienced in our clinic for evaluating the clinical relevance of DNA index (DI), clarifying those biological features and shedding some insights in the pathogenesis of testicular GCTs. Histological type and its incidences were seminomas in 35 adults, nonseminomatous germ cell tumors (NSGCTs) in 24 adults and prepubertal germ cell tumors (P-GCT) in 17 boys (9 in yolk sac tumors and 8 in teratomas). Totally 190 samples of paraffin embedded materials (with a mean of 2.5 samples per case) were histologically reconfirmed and employed the flow cytometry analysis with some modification of the Hedley's technique for analyzing the DNA ploidy and DIs. Coefficient of variation (CV) were acceptably ranged from 3 to 10%. In 58 evaluable cases with adult GCTs, 57 (98%) were revealed as DNA aneuploid, while DNA diploid tumor were observed in only one case with NSGCT. On the other hand, all specimens showed DNA euploid in P-GCT; DNA diploid in all teratomas and 6 yolk sac tumors, DNA tetraploid in other 3 yolk sac tumors. DNA aneuploid pattern was not apparently detected in children. Even in one adult case with pure yolk sac tumor and two adults with mature teratomas, all specimens were classified as DNA aneuploid. These results support the present hypothesis that the pathogenesis of P-GCTs is different from that of adult GCTs. DIs in adult NSGCTs (median DI = 1.56) are significantly lower than those in adult pure seminomas (median DI = 1.85) (p < 0.01). Although there was no significant correlation among the DIs in NSGCTs and the clinical staging of Japanese Urological Association, the distribution of DIs in NSGCT patients of the advanced extent were lower than that of the other extents of NSGCTs on the basis of Indiana University staging system (p < 0.05). In general, it has been postulated that the higher DI is paralleled to the more malignant nature of neoplasms. Nevertheless, this study conversely suggested that the lower DI in adult testicular GCTs is apt to related with high malignant potential determined by histological type and clinical stage. DNA heterogeneity was observed only in 4 of 23 cases with adult NSGCTs (17%), but 3 of these 4 cases (75%) with DNA heterogeneity were assigned as the advanced extent. These data suggest that the lower DI and the presence of DNA heterogeneity may have prognostic relevance for adult NSGCTs.