Nasal cavity, paranasal sinuses, nasopharynx

Inflammatory lesions

Inflammatory sinonasal polyp

Editorial Board Member: Molly Housley Smith, D.M.D.
Deputy Editor-in-Chief: Kelly Magliocca, D.D.S., M.P.H.
Bin Xu, M.D., Ph.D.

Last author update: 10 February 2022
Last staff update: 10 February 2022

Copyright: 2004-2024,, Inc.

PubMed search: Sinonasal[TI] inflammatory polyp

Bin Xu, M.D., Ph.D.
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Cite this page: Xu B. Inflammatory sinonasal polyp. website. Accessed February 26th, 2024.
Definition / general
  • Benign, nonneoplastic inflammatory outgrowth of sinonasal mucosa
  • Most common type of sinonasal polyp
  • Most common space occupying lesion of the sinonasal tract (J Clin Diagn Res 2014;8:FC04)
Essential features
  • Benign, nonneoplastic polyp characterized by edematous stroma infiltrated by mixed inflammatory cells
  • Chronic rhinosinusitis with nasal polyps
  • Nasal polyps
ICD coding
  • ICD-10: J33.9 - nasal polyp, unspecified
  • Most frequently occurs in the setting of chronic rhinosinusitis
  • Other risk factors include allergy, systemic vasculitis, cystic fibrosis, sensitivity to aspirin and nonsteroid anti-inflammatory drugs (StatPearls: Nasal Polyps [Accessed 12 January 2022])
Clinical features
  • Diagnosis can be rendered based on the typical endoscopic or histologic findings
Radiology description
  • Smooth soft tissue masses commonly originate in the ethmoid sinuses and protrude into the nasal cavity (Eur Radiol 2006;16:872)
  • Hypodense but may be hyperdense due to concurrent fungal infection or increased protein content
  • May demonstrate adjacent bony remodeling or erosion
Radiology images

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Coronal CT

Prognostic factors
  • Recurrence rate is approximately 60% in patients followed for at least 10 years
  • Presence of asthma is associated with increased risk of recurrence
  • Reference: Am J Rhinol Allergy 2021;35:449
Case reports
Clinical images

Images hosted on other servers:

Translucent polyps with a smooth surface

Gross description
  • Usually multiple and bilateral and involve nasal cavity and paranasal sinuses
  • Have translucent, moist or edematous cut surface
  • Broad base of attachment is present
  • Usually not destructive
Microscopic (histologic) description
  • Edematous, fibrotic or loosely myxoid stroma covered by respiratory epithelium
  • Infiltrated by mixed inflammatory cells, including lymphocytes, plasma cells, eosinophils, neutrophils and mast cells
  • Surface epithelium can show ulceration or squamous metaplasia
  • May have bizarre stromal cells (large and pleomorphic)
  • Submucosal glands are decreased or absent
  • Concurrent fungal infection may be seen
  • Rarely, osseous metaplasia may be present
Microscopic (histologic) images

Contributed by Bin Xu, M.D., Ph.D.

Edematous stroma

Mixed inflammatory infiltrate

Respiratory epithelium lining

Surface ulceration, squamous metaplasia

Stroma with hemorrhage


Sample pathology report
  • Nasal cavity, left, excision:
    • Inflammatory sinonasal polyp
Differential diagnosis
  • Sinonasal papilloma:
    • Inflammatory polyp lacks the epithelial proliferation, the thickened epithelial lining or the inverted growth pattern seen in sinonasal papilloma
  • Respiratory epithelial adenomatoid hamartoma:
    • Inflammatory polyp lacks the proliferation of respiratory epithelium and thickened basement membrane typical of respiratory epithelial adenomatoid hamartoma
  • Biphenotypic sinonasal sarcoma:
    • Can be polypoid but characterized by cellular spindle cells in the stroma showing biphenotypic neural and myoid differentiation
  • Rhabdomyosarcoma, embryonal (botryoid) type:
    • Can be polypoid but occurs in pediatric population and has a cambium layer of cellular small, blue, round cells showing skeletal muscle differentiation (i.e., positive for myogenin or MyoD1)
Board review style question #1
What is the most common polypoid lesion in the sinonasal cavity?

  1. Angiofibroma
  2. Inflammatory sinonasal polyp
  3. Respiratory epithelial adenomatoid hamartoma
  4. Sinonasal papilloma
Board review style answer #1
B. Inflammatory sinonasal polyp is the most common polypoid lesion and space occupying lesion in the sinonasal tract.

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Reference: Inflammatory sinonasal polyp
Board review style question #2

What is the diagnosis of this lesion excised from the left nasal cavity of a 35 year old woman?

  1. Biphenotypic sinonasal sarcoma
  2. Inflammatory sinonasal polyp
  3. Inverted sinonasal papilloma
  4. Respiratory epithelial adenomatoid hamartoma
Board review style answer #2
B. This is an inflammatory sinonasal polyp, a nonneoplastic benign lesion characterized by edematous stroma and inflammatory infiltrates.

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Reference: Inflammatory sinonasal polyp
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