Expression of metalloproteinases and tissue inhibitors of metalloproteinases in giant cell tumor of bone: an immunohistochemical study with clinical correlation.

The clinical behavior of giant cell tumors (GCTs) is unpredictable. To gain insight into this tumor's biological behavior, matrix metalloproteinases (MMPs) and tissue inhibitors of metalloproteinases (TIMPs) were studied. These substances play essential roles in wound healing and neoplastic invasion and metastasis. Paraffin-embedded tissue was collected from 18 cases of histologically benign GCT, with 17 treated by curettage and 1 by resection. Eight cases showed no recurrence after a minimum of 2.5 years, and 10 had local recurrence. One showed metastasis. Antibodies to MMP-9, MMP-2, TIMP-1, and TIMP-2 were applied by immunohistochemical methods. In all cases, MMP-9 was strongly expressed in giant cells predominantly in a diffuse pattern and was strong but focal in stromal cells. MMP-2 decorated stromal cells and giant cells heterogeneously. TIMP-1 was variably expressed in giant cells of the nonrecurrent cases and was strongly present in a diffuse or patchy distribution in the stromal cells in 6 of 8 cases. However, in 9 of 10 recurrent cases, TIMP-1 was expressed weakly by both giant and stromal cells. TIMP-2 was variably expressed in the giant cells of the nonrecurrent cases, but 6 of 8 nonrecurrent cases showed strong stromal cell positivity for TIMP-2. Weak staining for TIMP-2 was observed in 7 of 10 recurrent cases in the stromal cells and 9 of 10 recurrent cases in the giant cells. These results indicate that expression of MMPs and TIMPs differs in giant cells and stromal cells in the same tumor. More significantly, in contrast to the nonrecurrent giant cell tumors, there is an imbalance in the MMPs and TIMPs in the recurrent tumors with a net excess of MMPs. This unopposed expression of MMPs in GCTs may play a role in breakdown of extracellular matrix and tissue invasion. Finally, these markers may prove useful in predicting behavior in these tumors.