Significance of aneuploid stemlines in testicular nonseminomatous germ cell tumors

Background. Hyperpentaploidy in testicular nonse‐minomatous germ cell tumors (TNSGCT) has been associated with progression of disease of patients who initially had TNSGCT in Stage I. Methods. The authors used flow cytometry to investigate the relationship between ploidy and the clinical behavior in TNSGCT, focusing on hypertetraploid values (DNA index, > 2.00). Results. Patients with TNSGCT containing an aneuploid stemline with a hypertetraploid value more often had higher clinical stage of disease and a higher chance of relapse in advanced stages. The presence of multiple aneuploid stemlines in the tumors was found more frequently in patients who had higher clinical stage disease. Conclusions. The results suggest that the presence of highly aneuploid or multiple aneuploid stemlines in TNSGCT are associated with a clinically more malignant behavior.