This video provides a focused review of the clinical, radiographic, and pathological features of Giant Cell Tumor of Bone (GCTB). Radiographically, GCTB typically presents as a large, lytic, and expansive lesion located in the epiphysis (end) of a long bone, just beneath the joint space, sometimes exhibiting a "soap bubble" appearance. The presentation notes GCTB is a key differential diagnosis for lytic epiphyseal lesions in adults, alongside Aneurysmal Bone Cysts (ABC), Clear Cell Chondrosarcoma, and Chondroblastoma in younger patients. Pathologically, GCTB is characterized by abundant, exceptionally large, multinucleated giant cells embedded within a diffuse sheet of uniform, oval-to-round stromal cells. The critical diagnostic hallmark is the morphological similarity between the nuclei of the stromal cells and the nuclei within the giant cells. The tumor frequently shows secondary changes, including internal hemorrhage, hemosiderin deposition, and secondary aneurysmal bone cyst formation, which can lead to areas of fibrosis and spindling where giant cells may be sparse.
Giant Cell Tumor of Bone: Radiography and Pathology
0:03 Location and Radiography: Giant Cell Tumor of Bone (GCTB) characteristically arises in the epiphysis (end) of long bones, directly underneath the joint space.
0:20 Lytic Lesions: GCTB creates large, lytic lesions that expand outward. They are lytic because the normal mineralized bone is replaced by a cellular neoplasm, causing the area to appear darker on radiographs compared to surrounding white, mineralized bone. They are sometimes described as having a "soap bubble" appearance.
In younger patients, the differential includes Aneurysmal Bone Cysts (ABC), Clear Cell Chondrosarcoma (rare), and Chondroblastoma.
1:50 Pathology - Giant Cells: The tumor is defined by very large, abundant, multinucleated giant cells (osteoclast-like), often containing a large number of nuclei (sometimes over 100).
2:23 Pathology - Stromal Cells: The giant cells are organized within a diffuse sheet of uniform, oval to round (sometimes spindled) stromal cells.
3:30 Hallmark Feature: A key diagnostic feature is the morphological similarity in size, shape, and appearance between the nuclei of the stromal cells and the nuclei within the multinucleated giant cells.
3:55 Secondary Changes: GCTB frequently develops secondary aneurysmal bone cyst (ABC) formation, leading to areas of hemorrhage, hemosiderin (blood residue), and subsequent fibrosis/spindling in those regions (4:16).
4:43 New Bone Formation: GCTB can sometimes form new woven bone islands, but this feature is typically not abundant.