Proliferating cell nuclear antigen labelling index in localised pigmented villo-nodular synovitis and its relationship to the size of nodules.

Proliferating cell nuclear antigen (PCNA) is one of the cell cycle-related proteins directly involved in DNA synthesis. It is a marker of cellular proliferation and has been shown to correlate with ploidy and proliferative activity of cells. Its expression has been used to estimate the growth fraction of human cancer and its prognostic value. Pigmented villo-nodular synovitis (PVNS) is characterised by a nodular lesion in the paratendinous synovial tissue or, less frequently, in a joint. Whether PVNS is a neoplastic or inflammatory lesion remains controversial. We have studied immunohistochemical PCNA expression with pc10 monoclonal antibody in 16 paraffin sections, in 16 cases of localised PVNS, or giant cell tumour of tendon sheath. We have found significant correlation between the size of the lesions and PCNA-LI (labelling index).