Okay, let's tackle this question about fibrous dysplasia. The question is asking which statement is NOT true about fibrous dysplasia. First, I need to recall what fibrous dysplasia is. It's a benign bone disorder where normal bone is replaced by fibrous tissue and immature bone. It's part of the fibrous dysplasia-osteofibrous dysplasia spectrum.

The options aren't provided, but the correct answer is supposed to be the exception. Common facts about fibrous dysplasia: it can be monostotic or polyostotic, often causes pain and deformity, and is associated with McCune-Albright syndrome when polyostotic. It's not malignant, so malignancy transformation is rare. Also, the lesion is non-encapsulated and composed of fibrous stroma with woven bone.

Possible incorrect options might include something like "it's malignant," which is false. Another could be that it's associated with a specific gene mutation like FGFR3, but actually, it's related to GNAS mutations. Or maybe it's said to have a capsule, which it doesn't. Also, maybe a wrong statement about treatment, like it requires surgery always, but treatment is often conservative unless there's significant deformity or complications.

So the core concept here is the pathophysiology and characteristics of fibrous dysplasia. The correct answer would be the statement that contradicts these facts. For example, if an option says "fibrous dysplasia is a malignant tumor," that's the exception. Or if it mentions it's associated with a different syndrome than McCune-Albright, that's incorrect.

Each wrong option needs to be addressed. For instance, if an option claims it's a malignant condition, that's wrong because it's benign. If another says it's encapsulated, that's incorrect as it's non-encapsulated. Also, if a treatment option is suggested that's not standard, like chemotherapy, that's wrong.

Clinical pearls would be that fibrous dysplasia is non-encapsulated, part of the monostotic/polyostotic spectrum, and linked to GNAS mutations. Remembering that it's not a cancer and can lead to deformities is key. The exception would be any statement implying malignancy or incorrect mutation association.

**Core Concept**
Fibrous dysplasia is a developmental bone disorder characterized by replacement of normal bone with fibrous stroma and immature woven bone. It is non-neoplastic, lacks a true capsule, and may present as monostotic or polyostotic lesions. Pathognomonic histological features include "ground-glass" appearance on imaging.

**Why the Correct Answer is Right**
The incorrect statement is likely one claiming fibrous dysplasia is *malignant* or has a *true capsule*. Fibrous dysplasia is **benign** and **non-encapsulated**, with no risk of metastasis. Its pathogenesis involves activating mutations in the GNAS gene, leading to dysregulated osteoblast differentiation. Histologically, it shows haphazard trabeculae of woven bone in a fibrous matrix, distinct from neoplastic tumors.

**Why Each Wrong Option is Incorrect**
**Option A:** "Fibrous dysplasia is associated with malignant transformation" — Fibrous dysplasia rarely undergoes malignant transformation (e.g

✓ Correct Answer: D. Extramedullary