**Core Concept**
Antrochoanal polyp is a type of benign nasal polyp that originates from the maxillary sinus and grows into the nasal cavity, extending towards the nasopharynx. These polyps are characterized by their single stalk-like growth pattern and are often associated with chronic sinusitis.

**Why the Correct Answer is Right**
Antrochoanal polyps are typically unilateral, meaning they occur on one side of the nasal cavity. They usually arise from the mucous membranes of the maxillary sinus and grow towards the nasopharynx, often causing nasal obstruction, breathing difficulties, and loss of smell. The polyp's growth pattern is due to the accumulation of mucous and inflammatory cells, which can lead to the formation of a single stalk-like structure.

**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because antrochoanal polyps are not typically bilateral, nor do they usually occur in multiple sinuses simultaneously.
* **Option B:** This option is incorrect because antrochoanal polyps are not known to be associated with malignancy or cancerous changes.
* **Option C:** This option is incorrect because antrochoanal polyps do not usually present with multiple polyps or a diffuse polypoid mass.

**Clinical Pearl / High-Yield Fact**
Antrochoanal polyps are often treated with endoscopic sinus surgery, which involves the removal of the polyp and any underlying mucosal abnormalities. Early treatment can help prevent complications such as chronic sinusitis and nasal obstruction.

**Correct Answer:** B.