**Core Concept**
Antrochoanal polyp is a type of nasal polyp that originates from the maxillary sinus and extends into the nasopharynx. It is characterized by its benign nature and potential to cause nasal obstruction, sinusitis, and other respiratory symptoms.

**Why the Correct Answer is Right**
Antrochoanal polyps are typically solitary, unilateral growths that arise from the mucous membranes of the maxillary sinus. They are composed of a stalk-like structure, often containing a central core of inflammatory cells, and a terminal portion that invades the nasopharynx. The growth of antrochoanal polyps is thought to be related to chronic inflammation and mucous production within the maxillary sinus.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because antrochoanal polyps are typically benign and do not have a significant potential for malignant transformation.
**Option B:** This option is incorrect because antrochoanal polyps often present with unilateral nasal obstruction, not bilateral.
**Option C:** This option is incorrect because antrochoanal polyps are not typically associated with a significant increase in eosinophils.

**Clinical Pearl / High-Yield Fact**
Antrochoanal polyps are often associated with chronic maxillary sinusitis and may be treated with endoscopic sinus surgery to remove the polyp and address underlying sinus disease.

**Correct Answer: A.**