Ringertz Tumor (Inverted Papilloma / Schneiderian Papilloma)

Nomenclature

The Ringertz tumor is the eponymous name for sinonasal inverted papilloma (IP), named after Ringertz who first described the characteristic feature of epithelium inverting into the underlying connective tissue stroma. It is also called:

Schneiderian papilloma (most formal name - from the Schneiderian membrane)
Inverted papilloma (most commonly used in clinical practice)
Benign papilloma of the nasal cavity
Cylindrical cell papilloma (when referring to the oncocytic variant)

Types of Schneiderian (Sinonasal) Papillomas

There are 3 types, classified by growth pattern:

Feature	Inverted (Ringertz)	Exophytic (Fungiform)	Oncocytic (Cylindrical cell)
Frequency	Most common	Second	Rarest
Site	Lateral nasal wall, maxillary sinus	Nasal septum	Lateral nasal wall, maxillary sinus
Growth	Inverted into stroma	Outward (exophytic)	Mixed inverted + exophytic
M:F ratio	2-3:1	10:1	Equal
Peak decade	5th-6th	3rd-5th	5th-6th
Malignant transformation	5-15%	Exceptional	4-17%
HPV association	Controversial (22-26%)	Yes (low-risk HPV 6, 11)	None demonstrated
Molecular marker	EGFR mutations	-	KRAS mutations

Inverted Papilloma - Detailed Features

Epidemiology

Represents 0.4-4.7% of all surgically removed nasal tumors
Incidence: 0.74-2.3 new cases per 100,000 per year
The 2nd most common benign sinonasal tumor after osteoma; the most common Schneiderian papilloma
Peak: 5th and 6th decades, male predominance

Sites of Origin

Most common: Lateral nasal wall and maxillary sinus (especially the medial wall/fontanelle region)
Ethmoid region: 48%
Lateral nasal wall and maxillary sinus: 28%
Frontal sinus: only 2.5%
30% of cases involve multiple sites
Bilateral involvement is exceptional

Histology

Hyperplastic ribbons of basement membrane-enclosed epithelium growing downward (inverted) into the underlying stroma
Epithelium is multilayered: squamous or ciliated columnar cells mixed with mucocytes and transmigrating neutrophils
Distinct, intact basement membrane preserved
Stroma may show inflammatory cells

Endoscopic Appearance

Endoscopic view of inverted papilloma - polypoid lesion with pale, papillary surface protruding from the middle meatus

Fig. 50.1 - Typical endoscopic appearance: polypoid lesion with pale, papillary surface protruding from the middle meatus (Cummings Otolaryngology)

Etiology / Risk Factors

Organic solvent exposure - significantly related, with dose-response relationship
Smoking - risk factor for recurrence and malignant transformation (12x higher risk of malignancy in smokers; 26.4% vs 2.8% malignant transformation rate)
HPV - role controversial; HPV DNA found in ~13-26% but transcriptional activity unclear; high-risk subtypes (16, 18) found more in cases with dysplasia/carcinoma
EGFR mutations - characteristic molecular feature, preserved even in malignant transformation

Clinical Features

Symptoms:

Unilateral nasal obstruction with watery rhinorrhea (most common presenting symptom)
Unilateral rhinosinusitis (headache, facial pain) due to mechanical obstruction
Epistaxis
Anosmia (with extensive involvement)

Key clinical point: Any unilateral sinonasal mass should have inverted papilloma in the differential diagnosis.

Imaging

CT - primary modality; shows a soft-tissue mass with bony remodeling; focal hyperostosis is a common finding and helps identify the site of tumor origin
MRI - complementary; superior to CT in:
- Distinguishing mucus from papilloma (especially in the frontal sinus)
- Demonstrating the characteristic convoluted cerebriform pattern on T2/contrast-enhanced T1 - highly suggestive of IP
Combined CT + MRI for staging and surgical planning

Malignant Transformation

Rate: 5-15% (synchronous occurrence more common than metachronous)
Smoking confers 12x higher risk
Tumor types arising from IP:
- Squamous cell carcinoma (vast majority)
- Sinonasal undifferentiated carcinoma
- Mucoepidermoid carcinoma
- Verrucous carcinoma

Staging (Krouse Classification - most widely used)

Stage	Description
T1	Confined to nasal cavity, no extension to sinuses
T2	Involves ostiomeatal complex, ethmoids, and/or medial part of maxillary sinus
T3	Involves walls of maxillary sinus, frontal sinus, and/or sphenoid sinus
T4	Involves extrasinus structures (orbit, intracranial, pterygoid plates) OR carcinoma

Treatment

Surgical excision with negative margins is the treatment of choice. The key principle is removal of bone at the base to prevent recurrence.

Endoscopic endonasal approach - preferred when possible (avoids facial scar from lateral rhinotomy)
Open approach (lateral rhinotomy, medial maxillectomy) - for advanced tumors (T3/T4), frontal sinus disease, or when endoscopic access is limited
For malignant transformation: surgery + adjuvant radiotherapy

Recurrence:

Low with complete resection
Increased with incomplete removal, smokers, and multi-site disease
HPV low-risk types (especially HPV 6) promote recurrence

Key Summary Points

Ringertz tumor = Inverted papilloma = most common Schneiderian papilloma
Arises from the Schneiderian membrane (ectoderm-derived, unique to sinonasal tract)
Triad: local aggressiveness + recurrence + malignant potential (10-15%)
Most common site: lateral nasal wall and maxillary sinus
Classic presentation: unilateral nasal obstruction in a middle-aged male
CT shows soft-tissue mass with bony remodeling; MRI shows cerebriform pattern
Treatment: endoscopic excision with bone removal at the base
Smoking is the strongest modifiable risk factor for malignant transformation

Sources: Cummings Otolaryngology Head and Neck Surgery, Scott-Brown's Otorhinolaryngology Head & Neck Surgery, Sabiston Textbook of Surgery

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