Sinonasal polyposis

Sinonasal polyposis refers to the bilateral development of benign inflammatory masses arising from the mucosa of the nose and paranasal sinuses.[1] It is classified as a subgroup of chronic rhinosinusitis (CRS) and is designated chronic rhinosinusitis with nasal polyps (CRSwNP).[1] The condition is driven predominantly by type 2 inflammation characterized by eosinophilia and elevated interleukin-4, interleukin-5, and interleukin-13 cytokines, although non-type-2 endotypes exist.[1][2] On imaging, sinonasal polyposis characteristically produces bilateral mucosal opacification of the paranasal sinuses with polypoid soft-tissue masses protruding into the nasal cavity.[3] The disease follows a chronic relapsing course, and management centers on intranasal corticosteroids, biologic agents, and endoscopic sinus surgery for refractory cases.[1][4]

The current accepted designation is chronic rhinosinusitis with nasal polyps (CRSwNP), as defined in international consensus documents and the American Academy of Otolaryngology–Head and Neck Surgery (AAO-HNS) clinical practice guidelines. "Sinonasal polyposis" and "nasal polyposis" remain widely used synonyms.[5] Older literature may use "ethmoidal polyposis" when disease is centered on the ethmoid sinuses. The condition should be distinguished from the solitary antrochoanal polyp, which is a separate entity arising unilaterally from the maxillary sinus.[6] When associated with aspirin/NSAID hypersensitivity and asthma, the triad has been termed Samter triad, Widal triad, or more recently aspirin-exacerbated respiratory disease (AERD) or NSAID-exacerbated respiratory disease (N-ERD).[5][7]

• Prevalence: Estimated at 0.2% to 4% worldwide; endoscopic studies in a Swedish population report a prevalence of approximately 2.7% of adults.[1][8]
• Sex: At least a 2:1 male-to-female predominance.[8]
• Age: Incidence increases with age, peaking in the fifth to sixth decade, and is very uncommon before the third decade. Nasal polyps in childhood should prompt investigation for cystic fibrosis.[1][8]
• Distribution: Polyps most commonly originate from the ostiomeatal complex and ethmoid sinuses, with frequent involvement of the maxillary, frontal, and sphenoid sinuses. Disease is characteristically bilateral; unilateral polyposis warrants investigation for alternative diagnoses.[3][5][8]

Symptoms

• Nasal obstruction is the cardinal symptom, present in the vast majority of surgical candidates.[1]
• Hyposmia or anosmia is common and often the most distressing complaint.[1]
• Nasal discharge (anterior or postnasal), facial pressure, and sleep disturbance are frequent accompanying symptoms.[1][2]
• Polyp size correlates with subjective nasal obstruction but does not predict the severity of other symptoms.[1]

Examination Findings

• On anterior rhinoscopy or nasal endoscopy, polyps appear as pale, glistening, pedunculated masses arising from the lateral nasal wall, typically from the middle meatus. Color may range from yellow to white or pink.[1]
• Bilateral polyps are the hallmark; a unilateral mass should raise suspicion for inverted papilloma, antrochoanal polyp, or malignancy.[5][9]

Tempo and Complications

• CRSwNP follows a chronic course often lasting over 20 years.[8]
• Complications include secondary sinusitis, mucocele formation, and, in aggressive long-standing disease, sinus expansion with orbital involvement.[3]

Red Flags

• Unilateral disease, epistaxis, cranial nerve deficits, or bony destruction on imaging should prompt urgent evaluation for neoplasia.[5][9]

Sinonasal polyposis is frequently encountered as an incidental finding on dental radiographs, particularly panoramic images and CBCT acquired for implant planning or other dental indications.[10][11] The radiographic section below is organized by feature.

Location and Distribution

• Polyps characteristically produce bilateral, multisinus opacification, most commonly involving the ethmoid and maxillary sinuses, with variable frontal and sphenoid involvement.[3][12]
• The ostiomeatal complex is a characteristic site of origin; obstruction of the infundibulum and middle meatus is common.[3][13]
• On panoramic radiographs, the maxillary sinus floor is the region most likely to reveal abnormality, although panoramic sensitivity for sinus pathology is poor.[14][15]

Periphery and Shape

• Individual polyps appear as dome-shaped or lobulated soft-tissue masses protruding from the sinus wall into the sinus lumen or nasal cavity.[3][16]
• A solitary dome-shaped opacity arising from the sinus floor or walls may be indistinguishable from a mucous retention cyst on two-dimensional or unenhanced cross-sectional imaging.[3][16]
• When multiple polyps coalesce, the sinus may show complete opacification with loss of individual polyp contours.[3]

Internal Architecture

• On CT and CBCT, polyps demonstrate homogeneous soft-tissue attenuation.[3]
• Entrapped secretions between polyps may produce areas of increased density, creating a mixed-attenuation pattern that can simulate dystrophic calcification; this pattern is characteristic of superimposed allergic fungal rhinosinusitis (AFRS).[3]
• On panoramic radiographs, polypoid opacification appears as a diffuse radiopacity within the maxillary sinus, though the modality cannot reliably distinguish mucosal thickening from polyps.[14][17]

Effects on Adjacent Structures

• In long-standing or aggressive polyposis, sinus expansion with thinning and remodeling of the bony walls may occur, particularly in the ethmoid and maxillary sinuses.[3]
• Focal bone erosion is occasionally seen and is more suggestive of AFRS or should raise concern for neoplasia.[3][5]
• Obstruction of sinus ostia can lead to secondary mucocele formation with further bony expansion.[3]
• Polyps do not typically cause resorption of the roots of maxillary teeth; however, extensive maxillary sinus disease may abut the alveolar process and complicate implant planning.[10][11]

Extent and Cortical Involvement

• The Lund-Mackay scoring system is the standard method for quantifying sinus opacification, grading each sinus from 0 (clear) to 2 (complete opacification) with a maximum score of 24. CRSwNP typically produces higher Lund-Mackay scores than CRS without polyps.[3][18]
• Smooth bony remodeling without cortical destruction favors a benign inflammatory process; irregular lytic destruction suggests malignancy.[5][13]

Variants

• Central compartment atopic disease produces polyps arising predominantly from the middle turbinates with centrally located sinus opacification, sparing the lateral sinuses.[1]
• AFRS shows characteristic foci of hyperattenuation within opacified sinuses on CT, with sinus expansion and occasional bone erosion.[3]
• A solitary antral polyp (mucous retention cyst vs. polyp) is a common incidental finding on CBCT, reported in approximately 12–13% of maxillary sinuses, and is usually clinically insignificant.[10][19]

CT (Medical, Contrast-Enhanced)

Non-contrast CT is the study of choice for confirming CRSwNP and for presurgical planning, providing excellent bony detail of anatomic variants critical for safe endoscopic surgery.[13] Contrast-enhanced CT is not necessary for inflammatory disease but can help distinguish polyps from neoplasms: polyps demonstrate moderate-to-marked enhancement, whereas retention cysts do not enhance.[3]

MRI

MRI is indicated when osseous destruction, extra-sinus extension, or a suspected neoplasm is identified on CT.[5][13] Key MRI features include:

• Polyps show variable T1 and T2 signal depending on the stage of the polyp and the degree of desiccation of entrapped secretions.[3]
• Inflammatory polyps are typically T2 hyperintense, whereas desiccated secretions and allergic fungal mucin demonstrate T2 hypointensity—a useful discriminator from tumor.[3][13]
• MRI can distinguish tumor from obstructed secretions and identify intracranial or perineural extension.[9][13]
• The convoluted cerebriform pattern on T2-weighted and contrast-enhanced T1-weighted sequences is characteristic of inverted papilloma and helps differentiate it from inflammatory polyps.[13]
• Diffusion-weighted imaging with ADC mapping can further differentiate benign from malignant sinonasal lesions, with malignant tumors showing significantly lower ADC values.[20][21]

Sinonasal polyposis must be distinguished from other entities that produce sinus opacification or sinonasal masses. Unilateral disease, bony destruction, or atypical imaging features should prompt consideration of the following alternatives.

The highest-risk diagnostic pitfall is misidentifying a unilateral sinonasal malignancy or inverted papilloma as inflammatory polyposis. Any unilateral mass, bony destruction, or clinical red flags (epistaxis, cranial neuropathy) should prompt tissue biopsy and MRI before proceeding with routine polypectomy.[5][9]

Microscopic Features

• Polyps consist of edematous stroma with an inflammatory cell infiltrate covered by respiratory epithelium, often with areas of squamous metaplasia.[8][25]
• The inflammatory infiltrate is dominated by eosinophils in the majority of cases (type 2 pattern), accompanied by mast cells, lymphocytes, neutrophils, and plasma cells.[1][25]
• Basement membrane thickening, goblet cell hyperplasia, and subepithelial edema with reduced glandular density are characteristic remodeling features.[26]

Histopathologic Variants

• Structured histopathologic classification has identified distinct clusters based on the degree of fibrosis, eosinophilic versus neutrophilic infiltration, and hyperplastic/papillary epithelial changes, which may correlate with clinical endotypes and recurrence risk.[27]
• Antrochoanal polyps differ histologically, showing neutrophilic-predominant infiltration, prominent intramural cysts, and lower eosinophil counts compared with diffuse CRSwNP.[23][28]

Radiologic-Pathologic Correlation

• The homogeneous soft-tissue attenuation of polyps on CT corresponds to the edematous stroma; areas of increased density correlate with inspissated eosinophilic mucin, particularly in AFRS.[3]
• Tissue biopsy is essential for any unilateral mass or atypical presentation to exclude inverted papilloma or malignancy.[5][9]

Medical Therapy

• Intranasal corticosteroids (INCS) are first-line therapy and are recommended for all patients with CRSwNP (conditional recommendation, low certainty of evidence).[1][4]
• Saline irrigation is used as adjunctive therapy.[1]
• Short courses of systemic corticosteroids may be used for symptom flares but should be limited due to cumulative adverse effects.[1]
• Biologic agents (dupilumab, mepolizumab, omalizumab, tezepelumab) targeting type 2 inflammatory pathways are recommended for patients with inadequately controlled CRSwNP (conditional recommendation, moderate certainty of evidence). Dupilumab appears most effective for patient-reported outcomes and olfactory improvement.[4][29]
• Aspirin therapy after desensitization (ATAD) is suggested for patients with AERD (conditional recommendation, moderate certainty of evidence).[4]

Surgery

• Endoscopic sinus surgery (ESS) is indicated when medical therapy fails to control symptoms, typically after a minimum 8-week trial of INCS plus a short course of systemic corticosteroids.[1]
• Surgery aims to remove polyps and open sinus ostia to improve access for ongoing topical therapy.[1]
• Long-term quality-of-life improvements are maintained over 5 years after surgery, but recurrence is common: endoscopic polyp recurrence is reported in approximately 40% of patients at 18 months, and revision surgery is required in approximately 20% within 5 years. Five- and 10-year recurrence rates of approximately 30% and 66%, respectively, have been reported.[1][30]
• Postoperative INCS are essential and reduce the need for revision surgery.[1]

Prognostic Factors

• Asthma, AERD, and eosinophilic inflammation are predictors of more severe disease and multiple recurrences.[30][31]