Giant cell reparative granuloma of the distal skeletal bones. A report of five cases with immunohistochemical findings.

Giant cell reparative granuloma (GCRG) is a reactive bone lesion that most often involves the jaws. However, occasional cases of GCRG in the distal extremities have been reported, to which we add five cases. All the patients were young to middle-aged adults and had sharply bordered, lytic lesions. Histologically, all the lesions had areas of osteoclast-like giant cells and osteoblast mantled osteoid. Two of the cases had foci of osteoclast-like giant cells lining vascular spaces. In extragnathic locations, GCRG may simulate other osteolytic giant cells lesions such as giant cell tumour of bone and aneurysmal bone cyst (AnBC). Immunohistochemically, all cases showed positive staining of the stromal spindle cells for vimentin and actin, and of the osteoclast-like giant cells for CD68, vimentin and leucocyte common antigen. GCRG is a benign lesion and conservative therapy is curative. As GCRG may have histological features which resemble AnBC it may be considered to be the solid variant of AnBC.