Deoxyribonucleic acid ploidy in seminomas with and without syncytiotrophoblastic cells

Seminomas with human chorionic gonadotropin-producing syncytiotrophoblastic cells have been discussed as a distinctive subgroup with a worse prognosis. In a series of 50 seminomas (30 with immunohistochemically detectable syncytiotrophoblastic cells and 20 without syncytiotrophoblastic cells) deoxyribonucleic acid (DNA) ploidy was determined by flow cytometry in paraffin-embedded histopathological material. Comparatively, in 28 cases the DNA content was assessed by image cytometry on Feulgen-stained slides. DNA aneuploidy was detected in 49 seminomas (98%). No differences in the distribution of DNA index were observed between cases positive and negative for syncytiotrophoblastic cells (average DNA index 1.68 +/- 0.44 for positive cases and 1.71 +/- 0.52 for negative cases). Flow cytometry and image cytometry DNA index values showed a statistically significant correlation (p < 0.01). Intra-tumoral heterogeneity of DNA content was found in 2 seminomas negative for syncytiotrophoblastic cells. Multiploidy and hypertetraploidy were noted more often in negative cases also. DNA ploidy or distinct aneuploid stemlines did not correlate with histopathological tumor stage or clinical course. The results favor the notion that the occurrence of syncytiotrophoblastic cells in seminomas represents only an example of intra-tumoral variability of tumor cell differentiation and does not justify the definition as a separate subgroup with distinct biological behavior.