Antrochoanal polyp

Findings

Complete soft tissue opacification of the right maxillary sinus. The right osteomeatal unit is widened and there is polypoid extension of the soft tissue density through the nasal choana into the nasopharynx. The right middle turbinate is not clearly visualized, so the changes to the right osteomeatal unit may be postsurgical or due to bony remodeling secondary to the soft tissue mass. There is minimal septal bowing to the left. No intracranial or orbital invasion.

Differential Diagnosis:
- Antrochoanal polyp (or antral choanal polyp)
- Inverted papilloma
- Squamous cell carcinoma
- Adenocarcinoma
- Mycetoma
- Mucocele


Diagnosis: Antrochoanal polyp


Key points

Benign sinonasal inflammatory polyp

Clinical presentation
- Complete unilateral nasal obstruction
- Headaches
- Most common in teenagers
- Male > female

Imaging findings
- Well-defined, low -density mass
- Arises from maxillary antrum
- Extends through widened maxillary ostium into ipsilateral nasal cavity and then nasopharyngeal airway

CT
- May have increased density centrally, depending upon
Chronicity
Fungal colonization
Contrasted exam
- Peripheral enhancement of surrounding mucosa with no central enhancement
- Nodular enhancement rules out

MR
- Low T1—varies with chronicity
- High T2—near water-intensity
T1+contrast—similar to contrasted CT, peripheral not central enhancement

Pathophysiology
- Inflammatory polyp without allergic pathophysiology
Intramural retention cyst
Edematous hypertrophy of respiratory epithelium
No glandular distention
3-6% of all sinonasal polyps

Treatment
- Complete surgical removal of nasal and antral components
If antral base not removed, expect recurrence

Less common variants
- Nasochoanal polyp
- Sphenochoanal polyp
- Ethmochoanal polyp