**Question:** A 30 year old male presents to the clinic with swelling on the left side of his lower jaw. He gives no history of any previous surgical treatment. On extraoral examination, an asymmetrical face is seen. On palpation, bony hard swelling is appreciated. Under polarized light source, apple-green colour birefringence of amyloid deposited in fibrous connective tissue stroma is seen. The most probable diagnosis for this patient is:

A. Amyloidosis
B. Lymphoma
C. Ameloblastoma
D. Odontogenic keratocyst

**Correct Answer:** D. Odontogenic keratocyst

**Core Concept:**
Amyloidosis and odontogenic keratocyst both involve bony swelling in the oral cavity, but the key distinction lies in their pathological features. Amyloidosis is characterized by extracellular amyloid deposition, while odontogenic keratocyst is a benign epithelial cyst.

**Why the Correct Answer is Right:**
Odontogenic keratocyst (D) is a benign epithelial cyst that arises from the remnants of the dental lamina. It typically presents with a bony swelling in the oral cavity, and its apple-green birefringence under polarized light is due to the keratinized lining of the cyst.

**Why Each Wrong Option is Incorrect:**
A. Amyloidosis (Amyloidosis is characterized by extracellular amyloid deposition, not apple-green birefringence under polarized light.)
B. Lymphoma (Lymphoma is a malignant lymphoproliferative disorder, not a cyst presenting with bony swelling.)
C. Ameloblastoma (Ameloblastoma is a benign odontogenic tumor, not a cyst presenting with bony swelling.)

**Clinical Pearl:**
Odontogenic keratocyst, also known as Keratocystic odontogenic tumor, is a unique entity with distinct clinical and pathological features. While amyloidosis and lymphoma are different pathological entities, odontogenic keratocysts should be considered in the differential diagnosis of a bony swelling in the oral cavity along with ameloblastoma.