Differential Diagnosis of Unilateral Nasal Mass

Key principle: A unilateral nasal mass should be considered neoplastic until proven otherwise. Unlike bilateral disease (which is almost always inflammatory), unilateral nasal masses carry a significantly higher risk of malignancy or premalignancy.

Classification Overview

I. INFLAMMATORY / INFECTIVE

1. Antrochoanal Polyp (Killian's Polyp)

• Epidemiology: Children and young adults; most common unilateral inflammatory polyp
• Origin: Arises from the maxillary antrum (antral part), extends through the accessory ostium into the nasal cavity, then posteriorly to the choana
• Appearance: Pale/greyish, glistening, smooth surface, soft consistency
• Key features:
  • Single, pedunculated mass seen between septum and inferior turbinate anteriorly
  • Posterior rhinoscopy shows a globular, smooth mass in the choana
  • Insensitive to probing; does not bleed on touch (avascular)
  • A probe can be passed all around the mass
  • Bilateral attachment visible in both anterior and posterior rhinoscopy
• Imaging: CT shows opacified maxillary sinus with a soft tissue stalk through the accessory/natural ostium into choana
• Treatment: Endoscopic excision including the antral component (Caldwell-Luc or endoscopic middle meatal antrostomy) to prevent recurrence

2. Rhinosporidiosis

• Organism: Rhinosporidium seeberi (aquatic protist)
• Epidemiology: Endemic in South Asia (India, Sri Lanka); exposure to stagnant water; more common in males
• Appearance: Friable, red, strawberry-like or mulberry-like mass studded with white dots (sporangia visible through the mucosa). Very vascular — bleeds easily on touch
• Key features:
  • Polypoid, pedunculated
  • Nasal obstruction + profuse nasal bleeding
  • Disease remains localized; systemic dissemination rare
  • Granulation tissue base
• Differentiation: The "strawberry" / mulberry appearance with white dots is pathognomonic
• Histology: Sporangia in various stages of maturation within stroma
• Treatment: Surgical excision + diathermy of base; dapsone as adjunct

3. Fungal Ball (Mycetoma)

• Organism: Usually Aspergillus fumigatus
• Epidemiology: Older immunocompetent patients; often incidental finding
• Features: Unilateral sinus opacification; often asymptomatic, may have mild pressure, cacosmia, typical CRS symptoms
• CT hallmark: Hyperdense, calcified material with metallic density within sinus ("dirty-looking" sinus)
• No bony erosion (unlike invasive fungal sinusitis)
• Treatment: Endoscopic sinus surgery with evacuation

4. Allergic Fungal Rhinosinusitis (AFS)

• Epidemiology: Immunocompetent young adults with atopy/history of asthma
• Features: Thick, sticky, green-brown "peanut butter"-like mucin (allergic mucin); eosinophilic infiltrate; nasal polyps; often unilateral or markedly asymmetric
• CT: Heterogeneous opacification with central hyperdense areas (fungal concretions)
• IgE elevated; fungal cultures positive but low-grade colonization
• Differentiation from fungal ball: Polypoid nasal mucosa, eosinophilic mucin, atopic history vs. simple sinus opacification

5. Rhinoscleroma

• Organism: Klebsiella rhinosclematis
• Stages:
  1. Atrophic: resembles atrophic rhinitis — crusts, atrophy, discharge
  2. Granulomatous: nasal nodular mass, painless, non-ulcerative — this is the mass-presenting stage
  3. Cicatricial: scarring, nares stenosis
• Histology: Mikulicz cells (macrophages stuffed with bacilli) and Russell bodies (plasma cells with eosinophilic inclusions) — pathognomonic
• Differentiation: Granulomatous stage presents as hard, painless nasal mass; biopsy essential

6. Odontogenic Sinusitis

• Epidemiology: Fifth to seventh decades; history of dental implants, tooth extraction, or periapical pathology
• Features: Cacosmia (foul smell), unilateral CRS symptoms, purulent nasal discharge, unilateral nasal polyp
• CT: Unilateral maxillary sinus opacification; dental pathology at sinus floor
• Key clue: Dental history + cacosmia

II. BENIGN NEOPLASTIC

7. Inverted Papilloma (Schneiderian Papilloma — most important)

• Epidemiology: Most common benign sinonasal tumor; males > females; 5th–7th decades
• Origin: Lateral nasal wall (most common) — typically around the middle turbinate/ethmoid region
• Appearance: Irregular, grey-pink, firm mass with irregular surface; may resemble inflammatory polyp early on
• Key features:
  • Unilateral nasal obstruction + epistaxis
  • 10–15% malignant transformation (to SCC)
  • Local bone destruction
  • Associated with HPV (types 6, 11, 16, 18)
  • Insensitive to touch (differentiates from malignancy, which is sensitive/friable)
• CT hallmark: Hyperostosis at site of tumor attachment (lateral maxillary wall or ethmoid); focal bony thickening = site of origin
• MRI: Characteristic cerebriform/convoluted pattern on T2 — alternating stripes of low and high signal
• Differentiation from inflammatory polyp: Unilateral + lateral wall origin + CT showing hyperostosis; biopsy confirms
• Treatment: Complete resection with bone removal at base; endoscopic medial maxillectomy; high recurrence if incompletely excised — Cummings Otolaryngology

8. Juvenile Nasopharyngeal Angiofibroma (JNA)

• Epidemiology: Exclusively adolescent males (14–25 years); benign but locally aggressive vascular lesion; histologically a vascular malformation/hamartoma
• Origin: Pterygopalatine fossa / sphenopalatine foramen — pathognomonic location
• Appearance: Firm, pink-purple mass; highly vascular
• Key features:
  • Recurrent, profuse epistaxis (leading symptom) + unilateral nasal obstruction in an adolescent male
  • May extend to nasopharynx, nasal cavity, sphenoid sinus, infratemporal fossa, orbit, intracranially
  • Anterior bowing of posterior maxillary sinus wall (Holman-Miller sign) on imaging
  • Unilateral serous otitis media if Eustachian tube involved
  • Blood supply from internal maxillary artery (ECA) ± ICA branches
• CT: Intensely enhancing hypervascular mass at pterygopalatine fossa
• MRI: T2 hypointense "flow voids" within mass (vascular channels)
• Angiography: Pre-operative embolization required (dramatically reduces surgical blood loss)
• BIOPSY IS CONTRAINDICATED in clinic — risk of catastrophic hemorrhage
• Differentiation key: Adolescent male + pterygopalatine fossa origin + intense vascularity — do NOT biopsy before imaging — Cummings Otolaryngology

9. Lobular Capillary Hemangioma (Pyogenic Granuloma)

• Epidemiology: Bimodal — male adolescents and pregnant women; can occur any age (mean ~42 years)
• Origin: Anterior nasal cavity — Little's area or head of inferior/middle turbinate
• Appearance: Red to purple mass, usually < 1 cm; bleeds easily
• Key features:
  • Epistaxis (75%) > nasal obstruction (36%)
  • Associated with trauma, hormonal factors (pregnancy, contraceptives)
  • Rare: may fill entire nasal cavity + cause bone remodeling
• CT: Unilateral soft tissue mass, anterior location
• MRI: T2 hyperintense, T1 hypointense; vivid post-contrast enhancement
• Differentiation from JNA: Anterior location vs. pterygopalatine fossa; smaller; occurs in pregnant women/adolescents of both sexes; no Holman-Miller sign
• Treatment: Surgery; spontaneous regression in pregnancy-related cases — Cummings Otolaryngology

10. Osteoma

• Epidemiology: Most common benign sinonasal tumor overall (though JNA and inverted papilloma are most common in nasal cavity specifically); males, 2nd–5th decades
• Site: Frontal sinus (37–80%) > ethmoid > maxillary > sphenoid
• Appearance: Hard, white, multilobulated bony mass
• Key features:
  • Usually asymptomatic, incidental
  • Multiple osteomas → suspect Gardner's syndrome (APC mutation, colonic polyposis, soft tissue tumors)
  • Three types: ivory (dense, compact), mature (spongy), mixed
• CT: Dense, well-defined bony mass — diagnostic
• Differentiation: Hard consistency + bony density on CT is characteristic; no soft tissue component
• Treatment: Observation if asymptomatic; endoscopic resection if symptomatic — Cummings Otolaryngology

III. MALIGNANT

11. Squamous Cell Carcinoma (SCC)

• Most common sinonasal malignancy
• Epidemiology: 6th–7th decade; males > females; associated with wood dust, nickel, chromium, HPV
• Appearance: Irregular, pinkish-grey mass; friable, bleeds easily on touch; sensitive to touch (key differentiator from benign masses)
• Features: Nasal obstruction, epistaxis, foul-smelling blood-stained discharge; facial swelling/numbness (infraorbital nerve); loose teeth; orbital symptoms in advanced disease
• Imaging: Aggressive soft tissue mass with bony destruction/erosion on CT — bony erosion = malignancy until proven otherwise
• Differentiation: Bony erosion + friability + age + progressive symptoms + facial involvement
• Prognosis: ~50% 5-year survival; treatment = surgery + adjuvant radiotherapy

12. Adenocarcinoma

• Strongly associated with hardwood dust exposure (furniture/cabinet makers) — ethmoid sinus
• Origin: Ethmoid > maxillary sinus
• Features similar to SCC but occupational history is key
• Histology: Glandular architecture (intestinal type most common in hardwood workers)

13. Esthesioneuroblastoma (Olfactory Neuroblastoma)

• Origin: Olfactory epithelium at cribriform plate — roof of nasal cavity / superior nasal septum
• Epidemiology: Bimodal peaks (2nd and 5th decades)
• Features: Nasal obstruction + epistaxis + anosmia (loss of smell — important clue)
• Imaging: Mass at skull base/cribriform plate; intracranial extension common; "dumbbell" shape across cribriform plate on MRI; peripheral cysts at intracranial tumor margin are characteristic
• Markers: Positive for synaptophysin, chromogranin, NSE, S-100
• Differentiation: Location at cribriform plate + anosmia + neuroendocrine markers

14. Lymphoma (Sinonasal NK/T-cell Lymphoma — "Lethal Midline Granuloma")

• Epidemiology: More common in Asians; associated with EBV; males
• Features: Progressive destruction of midline facial structures — septum, palate, nasal bones; can cause saddle nose
• Appearance: Destructive, ulcerative mass; very destructive to intranasal structures
• Differentiation from Wegener's: Both destructive; lymphoma → ANCA negative, EBV positive; Wegener's → c-ANCA/PR3 positive, systemic vasculitis

15. Rhabdomyosarcoma

• Most common sinonasal malignancy in children
• Embryonal subtype predominates in children
• Rapidly growing, destructive mass; early orbital invasion; cervical lymphadenopathy
• Treatment: Primarily chemotherapy + radiotherapy (surgery in salvage)

IV. CONGENITAL / STRUCTURAL (Important in Children)

16. Nasal Encephalocele

• Herniation of brain tissue ± CSF through skull base defect
• Location: Midline — root of nose, inferior to nasal bones
• Key feature: Compressible, transilluminates, Furstenberg's test positive (enlarges with compression of jugular vein — raises intracranial pressure → pushes contents into mass)
• Pulsatile
• BIOPSY CONTRAINDICATED — risk of meningitis/CSF leak
• MRI is essential to confirm intracranial connection

17. Nasal Glioma (Nasal Cerebral Heterotopia)

• Ectopic glial tissue with no active intracranial connection (separated from brain; some may have fibrous stalk)
• Location: Midline — dorsum of nose or intranasal
• Features: Firm, non-compressible; Furstenberg's test negative (does not enlarge with jugular vein compression)
• Not pulsatile; does not transilluminate
• Differentiation from encephalocele: Non-compressible + negative Furstenberg's test + no intracranial connection on MRI

18. Dermoid Cyst

• Most common midline nasal mass in children
• Contains ectodermal and mesodermal elements (skin, hair, sebaceous glands)
• Features: Slow-growing, firm cystic mass over dorsum of nose; pit visible from nasal tip to glabella; may get infected; causes broadening of nasal dorsum
• Usually diagnosed within first 3 years of life
• No Furstenberg's sign; does not transilluminate

19. Rhinolith

• Calcified mass forming around a foreign body
• Appearance: Greyish-brown or greenish-black, very irregular surface, stony hard consistency
• Located between septum and turbinates
• Often brittle; breaks on manipulation
• CT: Calcified density — diagnostic

V. HOW TO DIFFERENTIATE — Key Summary Table

Red Flags for Malignancy in a Unilateral Nasal Mass

• Epistaxis that is recurrent and progressive
• Facial pain, numbness, swelling (infraorbital nerve involvement)
• Orbital symptoms — proptosis, epiphora, diplopia
• Loose teeth / hard palate involvement
• Anosmia (suggests esthesioneuroblastoma)
• Cervical lymphadenopathy
• Bony erosion on CT

Diagnostic Approach

1. History: Age, sex, occupation (wood dust → adenocarcinoma), geographic origin (endemic areas → rhinosporidiosis), dental history (odontogenic sinusitis)
2. Nasal endoscopy: Surface characteristics, site of origin, pulsatility, response to decongestant
3. CT sinuses (non-contrast first): Bony erosion → urgent; hyperostosis → inverted papilloma; bony density → osteoma; stalk through ostium → antrochoanal polyp
4. MRI: For soft tissue characterization, intracranial extension, convoluted pattern (inverted papilloma), flow voids (JNA), skull base defect (encephalocele)
5. Biopsy: Required for all except JNA and encephalocele (both contraindicated without imaging first)
6. Angiography ± embolization: For JNA before surgery