Fig. 3

Histology and CSF1 immunohistochemistry of giant cell tumor of bone, aneurysmal bone cyst, and giant cell reparative granuloma

a. Giant cell tumor of bone consisted of solid proliferation of histiocyte-like mononuclear cells with many osteoclast-like giant cells

b. The mononuclear tumor cells were negative for CSF1.

c. Aneurysmal bone cyst exhibited a blood-filled cystic space separated by fibrous septa. The fibrous septa consisted of mononuclear and fibroblastic spindle cells with osteoclast-like giant cells

d. The mononuclear cells were negative for CSF1.

e. Giant cell reparative granuloma was composed of diffuse proliferation of mononuclear to spindle cells without atypia accompanying osteoclast-like giant cells

f. The mononuclear cells were negative for CSF1.