Another study has shown that synovial tissue in PVNS abnormally secretes colony-stimulating factor 1, which recruits macrophages through binding to colony-stimulating factor 1 receptor to abnormally accumulate and locally form tumor-like masses, which constitute most of the tumor cell population and present as a tumor landscape effect in PVNS synovium [12]. The gene discussed is CSF1R; the disease is neoplasm.