There are contrary opinions about the nature of pigmented papillary-nodular synovitis (PPNS) in the scientific literature. Despite the fact that some authors express the opinion that PPNS is an inflammatory process, most authors classify this disease as a neoplasia with aggressive destructive local behavior and a high recurrence rate of 50-70% [3, 8, 10]. It remains undisputed that PPNS is accompanied by a constant uncontrolled proliferation of synovial cells; at the same time, the mechanisms that cause this proliferation, as before, are still unknown [9].

The aim of the work is to study the effect of cytotoxic lymphocytes (natural killers) on the progression of pigmented papillary-nodular synovitis.