Introduction. There is a pathogenetic parallel between the aging process and carcinogenesis. About half of cancer cases are formed in recipients older than sixty-five, including prostate cancer. This is facilitated, in particular, by the departure from the immune control of the cells surrounding the tumor, which can express a number of signal proteins that suppress the protective response. This includes the programmed cell death protein (PD-1) and its ligand PD-L1. Purpose of the study. To develop and evaluate the possible application of original immunohistochemical models in people of older age groups with prostate cancer with the aim of developing further paths for diagnosis and treatment. Materials and methods. For immunohistochemical analysis, data from the control group of 5 men, as well as 24 patients with prostate cancer of middle and old age were used. For this, the PD-L1 ligand was chosen. The significance of differences in mean and relative quantitative values was determined by Student's t-test. Calculations were performed using Microsoft Excel software using the Statistica 6.0 package. Results. It was shown that immunohistochemical parameters of PD-L1 expression are directly dependent both on the stage of the process, progressing from II to III, and on age, when, on the contrary, regression is detected (p