Relationship between binuclear and multinuclear cells in giant cell tumor of bone

Giant cell tumor of bone (GCT) consists of stromal and multinuclear type tu mor cells. Although most people believe that the stromal cells are mononucl ear, we recently found the existence of many binuclear cells among stromal cells using DNA cytofluorometric examination. This study, using 18 tumors o f GCT was conducted to elucidate the cell biological significance of the bi nuclear cell, especially its relationship to multinuclear cell formation or tumor cell proliferation. The investigation was carried out by means of DN A-RNA cytofluorometry with acridine orange (AO) and histological method. Us ing fluorescence microscopic observation, we counted the numbers of both mo nonuclear and binuclear cells and calculated the index of % BNC, which expr esses the frequency (percentage) of binuclear cells in a population of mono nuclear and binuclear cells. The index of % S-G2 obtained by DNA-RNA cytofl uorometry showed the frequency (percentage) of mononuclear cells in the S a nd G2 phases of the cell cycle. In the histological study, we counted the n umbers of multinuclear giant cells with more than 3 nuclei in the cytoplasm and stromal cells including mononuclear and binuclear cells and calculated MNS/SC, which showed the percentage of multinuclear cells in the stromal c ells in the microscopic field. Eight tumors showed a value of % BNC greater than 10% and 2 had a value of 40%. The index of % BNC significantly correl ated with the average value of MNC/SC in all tumors. There was no significa nt correlation between % BNC and the average value of % S-G2 in 18 tumors a lthough 4 tumors having a % BNC value greater than 20% showed a % S-G2 valu e greater than 12% in 18 rumors. These results revealed the presence of man y binuclear cells among stromal cells of GCT and suggested that these binuc lear cells might be formed in association with the active proliferation of mononuclear cells and closely relate to the formation of multinuclear giant cells.