Flow cytometry analysis of ploidy and proliferation activity in classical and spermatocytic seminoma

In a series of 49 cases of seminomas, namely 19 classical seminomas, 21 seminomas with syncytiotrophoblastic cells and 9 spermatocytic seminomas, DNA ploidy and S-phase cell fraction of the cell cycle were estimated in paraffin-embedded histopathological material. DNA aneuploidy was detected in 16/19 classical seminomas (84%), in all seminomas with syncytiotrophoblastic cells (100%) and in 6/9 spermatocytic seminomas (67%). In three cases two distinct aneuploid stemlines were detected, in four cases regional variations in ploidy level were observed, clearly proving cellular heterogeneity within the studied specimens. No significant differences in distribution of ploidy levels of aneuploid tumors were detected either between distinct groups of seminomas or in relation to the age of the patients. On the other hand, mean values of S-phase cell fractions in our material offer statistically highly significant differences between defined groups of tumors. Spermatocytic seminomas had the highest level of proliferation activity, which is in contrast with the clinicopathological observations (relatively slow growth, rare occurrence of metastases, local malignancy). The results of proliferation activity analysis and the relatively highest incidence of diploid tumors support the theory of different origin of spermatocytic seminomas in comparison with other germ cell tumors.