A 50-year-old lady presented with a 3-month history of pain in the lower third of the right thigh. There was no local swelling; tenderness was present under deep pressure. Plain X-rays showed an ill-defined intramedullary lesion with blotchy calcification at the lower end of the right femoral diaphysis, possibly enchondroma or chondrosarcoma. Sections showed a cartilaginous tumor. Which of the following histological features (if seen) would be most helpful to differentiate the two tumors?

**Core Concept**
The question tests the ability to differentiate between enchondroma and chondrosarcoma, two types of cartilaginous tumors that can occur in the bone. Enchondroma is a benign tumor, while chondrosarcoma is a malignant tumor. The key to differentiation lies in the histological features of these tumors.

**Why the Correct Answer is Right**
The correct answer is based on the understanding of the histological features of enchondroma and chondrosarcoma. Enchondromas typically show a lobular pattern of cartilage with a mix of benign cells and a characteristic "chicken wire" calcification. Chondrosarcomas, on the other hand, show a more disorganized and pleomorphic pattern of cartilage with a higher cellularity and a more aggressive growth pattern. The presence of **myxoid matrix** in chondrosarcoma is a key feature that differentiates it from enchondroma.

**Why Each Wrong Option is Incorrect**
* **Option A:** The presence of binucleated cells is a feature of chondroblastoma, not enchondroma or chondrosarcoma.
* **Option B:** The presence of giant cells is a feature of osteochondroma, not enchondroma or chondrosarcoma.
* **Option D:** The presence of hemosiderin-laden macrophages is a feature of giant cell tumor, not enchondroma or chondrosarcoma.

**Clinical Pearl / High-Yield Fact**
The histological features of enchondroma and chondrosarcoma can be remembered using the mnemonic "LOBULAR" for enchondroma (Lobular pattern, Benign cells, Chicken wire calcification, Unilocular) and "PLEOMORPHIC" for chondrosarcoma (Pleomorphic pattern, Higher cellularity, Low-grade matrix, Osteoid formation).

**Correct Answer:** C.

✓ Correct Answer: B. Tumor permeation between bone trabeclae at periphery