**Core Concept**
Mucocele of the appendix is a rare condition characterized by the accumulation of mucus within the appendix, leading to its distension and potential rupture. This condition is often associated with an obstruction of the appendix, which can be caused by various factors such as a tumor, foreign body, or chronic inflammation.

**Why the Correct Answer is Right**
The accumulation of mucus in the appendix is a result of an abnormal communication between the appendix and the intestinal lumen, allowing mucus to enter the appendix and accumulate. This can lead to an increase in the pressure within the appendix, causing it to distend and potentially rupture. **Option C: Mucosal gland hyperplasia and accumulation of mucus** is the correct answer because it accurately describes the pathophysiological mechanism underlying mucocele of the appendix.

**Why Each Wrong Option is Incorrect**
**Option A:** is incorrect because it does not accurately describe the pathophysiology of mucocele of the appendix. **Option B:** is also incorrect because it is a vague term that does not specifically relate to the condition.

**Clinical Pearl / High-Yield Fact**
It is essential to consider mucocele of the appendix in the differential diagnosis of acute appendicitis, especially in cases where the appendix is not inflamed. A mucocele of the appendix can mimic the presentation of acute appendicitis, but it may not respond to standard treatments.

**Correct Answer: C. Mucosal gland hyperplasia and accumulation of mucus**