Antrochoanal Polyp and Other Antral Nodules: Causes, Imaging, and Management

Nodules in the Maxillary Sinus Antrum: Differential Diagnosis

The maxillary antrum (largest paranasal sinus) can harbor various nodular lesions. Accurate diagnosis requires correlating imaging, endoscopy, and histopathology.

Common Etiologies

Lesion	Key Features	Imaging (CT/MRI)	Management
Antrochoanal Polyp (ACP)	Benign, unilateral, teardrop-shaped; arises from medial maxillary wall → extends through accessory ostium → choana → nasopharynx	Soft-tissue mass filling maxillary sinus, passing through ostium, in nasal cavity; no bone destruction	Endoscopic sinus surgery (ESS) with complete removal of stalk; low recurrence
Inflammatory Polyp	Chronic rhinosinusitis (CRS) with polyps; often bilateral, multiple	Diffuse sinus opacification, polypoid thickening	Medical (intranasal steroids, saline irrigation, biologics for CRS w/ NP) ± ESS
Mucous Retention Cyst (Mucocoele)	Benign, mucus-filled, lined by epithelium; usually asymptomatic, incidental	Thin-walled, non-enhancing, dome-shaped; may displace sinus walls	Observe if asymptomatic; marsupialization if symptomatic/large
Fungal Ball (Mycetoma)	Aspergillus spp.; dense fungal debris + mucus; unilateral	Hyperdense on CT (calcium salts); “double density” sign; no invasion	ESS with complete removal; antifungals not needed
Odontogenic Lesions	Radicular cyst, dentigerous cyst, ameloblastoma from maxillary teeth	Well-defined, corticated, associated with tooth apex; may erode sinus floor	Enucleation + dental treatment
Neoplasms (Benign)	Inverted papilloma (locally aggressive, 10% malignant transformation), osteoma, fibroma	Inverted papilloma: enhancing, heterogeneous, bone remodeling	Complete endoscopic resection; close surveillance for IP
Malignant Tumors	Squamous cell carcinoma (most common), adenocarcinoma, melanoma, lymphoma, sarcoma	Bone destruction, soft tissue invasion, perineural spread, lymphadenopathy	Multidisciplinary: surgery ± radiation ± chemo; palliative if advanced

Diagnostic Workup

1. Nasal endoscopy (office).
2. CT sinuses (bone algorithm) — primary for anatomy, bone changes.
3. MRI if soft tissue extension, perineural spread, or intracranial involvement suspected.
4. Biopsy (endoscopic or image-guided) for definitive histology if neoplasm suspected.

Red Flags for Malignancy

• Unilateral persistent obstruction, epistaxis, facial pain/numbness, dental loosening, proptosis, palatal ulceration, cervical lymphadenopathy.

Referral to rhinology/ENT specialist for any antral mass on imaging.