Question:medium
A 30-year-old male presents with swelling around the knee joint. Histopathological examination of the swelling shows many giant cells interspersed with mononuclear cells. What is the probable diagnosis?
A 30-year-old male presents with swelling around the knee joint. Histopathological examination of the swelling shows many giant cells interspersed with mononuclear cells. What is the probable diagnosis?
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Young adult, lesion at the knee epiphysis, sheets of mononuclear cells with many osteoclast-like giant cells.
Updated On: Jun 23, 2026
- Osteosarcoma
- Ewing's sarcoma
- Giant cell tumour
- Chondrosarcoma
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The Correct Option is C
Solution and Explanation
Pattern recognition wins here: many giant cells plus mononuclear cells, sited at the knee, in a young adult, points straight to a giant cell tumour of bone, option 3.
GCT favours the epiphysis of long bones near the knee, the distal femur and proximal tibia, in patients aged 20 to 40. On gross exam it is a red-brown, often cystic mass. Microscopically you see uniform oval mononuclear (the true neoplastic) cells studded with osteoclast-like giant cells that can pack in well over a hundred nuclei, along with frequent mitoses, areas of hemorrhage and reactive bone.
The distractors have different signatures: osteosarcoma makes malignant osteoid, Ewing's sarcoma is a small round blue cell tumour, and chondrosarcoma forms malignant cartilage. None of them is defined by sheets of osteoclast giant cells, so GCT is the diagnosis.
Ref: Robbins Basic Pathology, 9th edn.
GCT favours the epiphysis of long bones near the knee, the distal femur and proximal tibia, in patients aged 20 to 40. On gross exam it is a red-brown, often cystic mass. Microscopically you see uniform oval mononuclear (the true neoplastic) cells studded with osteoclast-like giant cells that can pack in well over a hundred nuclei, along with frequent mitoses, areas of hemorrhage and reactive bone.
The distractors have different signatures: osteosarcoma makes malignant osteoid, Ewing's sarcoma is a small round blue cell tumour, and chondrosarcoma forms malignant cartilage. None of them is defined by sheets of osteoclast giant cells, so GCT is the diagnosis.
Ref: Robbins Basic Pathology, 9th edn.
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