Patient aged 30 yr presented with swelling around knee Aspirate shows giant cells and mononuclear cells Most likely diagnosis is
**Core Concept**
Giant cell tumor of bone is a rare, benign, but locally aggressive neoplasm that typically affects the epiphyseal region of long bones, often presenting with pain and swelling. The presence of giant cells and mononuclear cells in the aspirate is suggestive of this diagnosis.
**Why the Correct Answer is Right**
The giant cells in the aspirate are likely osteoclast-like giant cells, which are characteristic of giant cell tumors. These cells are thought to be derived from the mononuclear stromal cells and are responsible for the bone destruction seen in this condition. The presence of giant cells along with mononuclear cells, which are likely the neoplastic cells, is diagnostic of giant cell tumor.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because giant cell tumor is a distinct entity from osteosarcoma, which typically presents with more aggressive features and a different histological appearance.
**Option B:** This option is incorrect because rheumatoid arthritis typically presents with a more systemic symptoms and a different joint involvement, and the aspirate would show more inflammatory cells.
**Option C:** This option is incorrect because osteonecrosis typically presents with a history of trauma or steroid use, and the aspirate would show more necrotic cells.
**Option D:** This option is incorrect because pigmented villonodular synovitis (PVNS) typically presents with a more chronic course and a different histological appearance, with a predominance of histiocytes and hemosiderin-laden macrophages.
**Clinical Pearl / High-Yield Fact**
Giant cell tumor of bone is a benign but locally aggressive tumor that requires prompt treatment to prevent local recurrence and potential malignant transformation.
**Correct Answer:** B. Pigmented villonodular synovitis (PVNS) is not correct as the correct answer is not provided in the question.