[Cellular biological study of giant cell tumor of bone: a 10-year summary]

This article is a summary of the main research accomplishments on giant cell tumor of bone (GCT) carried out in this laboratory in the past ten years. The stromal cells (STC) in GCT have long been regarded as a single neoplastic element. By means of immunological method they are segregated into EA rosette-forming cells (RFC) and non-rosette-forming cells (NRFC). It is herein demonstrated that RFC are macrophages of the defensive mechanism, while NRFC bear the hallmarks of neoplastic cells. The views concerning the nature of the multinucleated giant cells (MGC) so far remains controversial. One of the authors, on the basis of the survival time in thin vitro culture, classifies them into short survival MGC (S-MGC) and long survival MGC (L-MGC). Immunological and cytochemical evidences indicate that S-MGC are similar to osteoblasts and foreign-body giant cells and express macrophage antigen. Moreover, macrophages in GCT can actually form MGC. L-MGC, however, present characteristics of neoplastic cells which are known to be able to form tumor giant cells. Thus the concept of GCT has been renovated. Evaluation of the aggressiveness of GCT is important and challenging, as the Jaffe grading system is no longer widely considered valid. In our laboratory this problem has been approached by cytomorphometry, nuclear DNA-cytometry and multifactor analysis techniques. Parameters which are conducive to predicting the prognosis of GCT are found, which would render help to clinical diagnosis and research of this semimalignant tumor.