Unusual immunocytochemical and ultrastructural features of synovial fluid cells in multicentric reticulohistiocytosis. A case report.

We present the first report in which cells in synovial fluid from a patient with multicentric reticulohistiocytosis (MRH) were studied by immunocytochemistry for correlation with routine light and electron microscopy. MRH cells stained predominantly for lymphocyte-related surface antigens and not for the monocyte marker LEU M3 (CD14). These findings suggest a lymphocytic origin of MRH cells and not a histiocytic origin, as previously suggested. In addition, large numbers of membrane-bound, electron-dense, secretory-type granules were found ultrastructurally in the cytoplasm of these cells.