Abstract: | Cytological characterist;cs of three main cellularelements iii benign and malignant giant cell tumorof bone were investigated by cytochemistry, tissueccilture. electron microscopy and microspectropho.toinetry. The macrophage (MO), as identified byEA rosette assay, and the multinucleated giant celf(MGC) had similar enzyme activities, which differedfrom those of the non rosette-forming cell (NRFC).MO and MGC of malignant giant cell tumor ofbone (MCCT) did not proliferate in vitro while ;tsNRFC could maintain seri81 growtfi with concomitant formation of some multinuclear cells which areclifferent from MCC inthe light and eleccronof atypical MCCs werecertain aspects. Under bothmicroscope a small numberfound in MGCT. The;r niiclei varied in size and shape. The NRFC in MGCTshowed more prominent ritypical ultrastructuralfeatures. Part of the NRFCs had aneuploid DNAcontent above 4C (-4C), which is generally considered as the evidence of rnalignancy. Some nucleii" the MGCs of MGCT contained }40 DNA content, but not those in MGCs of benign giant celltumor of bone. Usually, no aneupaoidy was detectedin MO of all the samples with the exception of oneMGCT sample. in which l O% M¢ contains :4C DNAcontent. Iri the in virro labelling, :II-TdR labelledNRFC were in varying percentage, but labelled MOand MGC were infrequently found. The circumstantial evidences suggest a close relationship exists be.tween M¢ and MGC: but NRFC presents neoplasticfeaturea. The atypical giant cells in MGCT mightbe of tumor origin. |