**Question:** Mucocele is commonly seen in sinus:

A. Maxillary sinus
B. Ethmoid sinus
C. Sphenoid sinus
D. Frontal sinus

**Correct Answer:** D. Frontal sinus

**Core Concept:** Mucocele is a benign cystic lesion that develops when mucus-producing cells of the paranasal sinuses become obstructed, leading to an accumulation of mucus within the sinus structure.

**Why the Correct Answer is Right:** Mucocele commonly occurs in the frontal sinus due to its unique anatomy. The frontal sinus is the most anterior of the paranasal sinuses, situated above the eyebrows. Its narrow ostium (opening) to the nasal cavity makes it prone to obstruction, which leads to mucus accumulation and mucocele formation.

**Why Each Wrong Option is Incorrect:**

A. Maxillary sinus (Mucocele) is less common in the maxillary sinus as compared to frontal sinus due to its larger ostium size and better drainage.
B. Ethmoid sinus (Mucocele) is less common because it has a complex network of ostia, which reduces the risk of obstruction and mucocele formation.
C. Sphenoid sinus (Mucocele) is less common as it has a wide ostium, ensuring good drainage and reducing the likelihood of obstruction and mucocele formation.

**Clinical Pearl:** Understanding the anatomy of the paranasal sinuses and their ostia (opening to the nasal cavity) is crucial for recognizing mucocele lesions. This knowledge aids in accurate diagnosis and proper management of these lesions, preventing misdiagnosis and unnecessary interventions.