Contribution of cell proliferative activity to malignancy potential in testicular seminoma.

Testicular anaplastic seminoma, which has a high mitotic activity, is regarded as more malignant than typical seminoma, although its prognosis is still unclear. To determine whether seminoma with relatively greater malignancy potential can be identified based on the cell proliferative activity, the mitotic rate (MR; mitotic count per high-power field), mitotic index (MI; mitotic count per 1000 cells), Ki-67 labeling index (Ki-67 LI; the percentage of positive cells) and proliferating cell nuclear antigen LI (PCNA LI; the percentage of positive cells) were histologically examined in 44 patients. The MI, Ki-67 LI and PCNA LI in patients with metastatic disease were significantly higher than those in patients without metastatic disease, and the MI in patients with fatal disease was significantly higher than those in patients cured of the disease. However, these distributions of the MI, Ki-67 LI and PCNA LI values overlapped for both pairs of groups. There were no significant differences in the MR. These results suggest that the cell proliferative activity makes a small contribution to the malignancy potential in testicular seminoma, with the activity being not necessarily indicative of metastasis and prognosis.