Metachronous multicentric giant-cell tumor of the bone in the lower limb. Case report and Ki-67 immunohistochemistry study.

Multicentric giant-cell tumors of the bone (GCTs) are rare. Little is known about the mechanisms by which these tumors spread and how 1% of GCT turn out to be multicentric. We report the case of a 19-year-old woman with metachronous multiple and recurrent GCTs that were unusual in their pattern of progression along the right lower limb over a 23-year period. Histology showed no evidence of malignant transformation. The treatment was repeated curettage and packing with cement. This did not permit a wide surgical margin, but avoided amputation and preserved full limb function. We tested the proliferation index marker Ki-67 in the tumor specimens. Ki-67 expression was limited to the mononuclear cell component of the tumors. The proliferation index was similar in each new tumor and higher in recurrences for each location. In this case, proliferation was initially low in the new tumor location, despite the time difference and independent from the initial clone evolution. Proliferation index increased in recurrent GCTs after marginal margin resection.