The aim of our study was to assess the relationship between the serum lactate dehydrogenase isoenzyme 1 (S-LDH-1) activity in patients with testicular germ cell tumors and the number of copies of the short arm of chromosome 12 (12p) present in tumor. Twenty-seven adult patients with measurable tumor lesions were studied. Twenty-five had three or more copies of chromosome 12 per cell in the tumors. Nineteen had one or more copies of a specific chromosomal abnormality, an isochromosome of the short arm of chromosome 12, i(12p). Fourteen had increased S-LDH-1 levels. S-LDH-1 activity correlated significantly with the product of total tumor volume and the total number of copies of the short arm of chromosome 12 present per cell (total tumor 12p). We conclude that the total number of copies of the short arm of chromosome 12 in the tumors is most probably a factor contributing to the LDH-1 activity released from the 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.