What is the management of inverted papilloma?

Management of Inverted Papilloma

Complete surgical resection with removal of all diseased mucosa and mucoperiosteum at the attachment site, followed by drilling or coagulation of the base, is the definitive treatment for inverted papilloma, with endoscopic approaches achieving equivalent or superior outcomes compared to open procedures when performed by experienced surgeons. 1

Classification and Risk Stratification

The International Consultation on Urologic Disease-European Association of Urology (ICUD-EAU) recommends applying WHO/ISUP grading criteria to inverted urothelial lesions, which are classified as: 1

• Inverted papilloma: Non-hyperplastic, non-atypical urothelium with endophytic growth and peripheral palisading 1
• Inverted PUNLMP: Hyperplastic urothelium growing in endophytic pattern with negligible progression risk 1
• Inverted papillary urothelial carcinoma, low-grade, non-invasive: Increased cellularity and loss of polarity with mild to moderate cytologic atypia 1
• Inverted papillary urothelial carcinoma, high-grade: Greater loss of epithelial order with increased nuclear atypia, which may be invasive or non-invasive 1

Note: This classification applies when inverted growth pattern is prominent or predominant; mixed exophytic/inverted tumors should be graded by the highest grade component. 1

Surgical Management Algorithm

Primary Treatment Approach

Endoscopic resection is the preferred surgical approach for most inverted papillomas, achieving recurrence rates of 12.8% compared to 17.0% for lateral rhinotomy with medial maxillectomy and 34.2% for limited resections. 2, 3

The surgical technique must include: 4

• Complete excision of all diseased mucosa and mucoperiosteum at the tumor attachment site
• Removal of a cuff of normal-appearing mucosa surrounding the attachment site
• Drilling and/or coagulation of the underlying bone at the attachment base
• Attachment-oriented approach: Surgical strategy determined by the location of tumor attachment site rather than staging alone 4

When to Consider Open or Combined Approaches

Open procedures (lateral rhinotomy with medial maxillectomy) or combined endoscopic-open approaches should be considered when: 3, 5

• Tumor attachment sites are inaccessible endoscopically
• Extensive bone destruction is present
• Endoscopic exploration reveals attachment sites requiring adjunctive open procedures 3

Management of Incompletely Resectable Disease

For the small subset with incompletely resectable inverted papilloma, definitive radiotherapy using 65-70 Gy will achieve local control in the majority of patients. 5

Management Based on Malignant Potential

Synchronous Malignancy (Present at Diagnosis)

When squamous cell carcinoma is identified with inverted papilloma (occurs in 7.1% of cases): 2, 5

• Complete surgical resection remains primary treatment
• Postoperative radiotherapy should be added for the majority of these patients 5
• Probability of cure is approximately 50% when malignancy is present 5
• Risk of local recurrence and death from tumor is significantly increased 5

Surveillance for Metachronous Malignancy

Long-term surveillance is mandatory because metachronous carcinoma develops in 3.6% of cases, with mean time to transformation of 52 months (range 6-180 months). 2

Surveillance protocol should include: 2, 6

• Regular endoscopic examination to detect recurrence before extensive growth occurs
• Serial imaging (CT and MRI) to assess for recurrence and bone involvement 6
• Continued follow-up beyond 5 years, as recurrent disease and metachronous carcinoma can develop after prolonged periods 2
• Estimated malignant potential for recurrent disease is up to 11% 2

Critical Pitfalls to Avoid

• Inadequate initial resection: Limited procedures like simple polypectomy or Caldwell-Luc approaches have 34.2% recurrence rates versus 12.8% for complete endoscopic resection 2
• Failure to remove attachment site: The attachment site must be completely excised with surrounding normal mucosa and underlying bone treated with drilling/coagulation 4
• Premature discontinuation of surveillance: Recurrence and malignant transformation can occur after many years; lifelong follow-up is recommended 2
• Misclassification of inverted lesions: Failure to apply standardized WHO/ISUP criteria leads to inconsistent terminology and inappropriate management 1
• Inadequate staging: Both CT and MRI should be used preoperatively to define extent, bone involvement, and guide surgical approach 6

Special Considerations

• Atypia or dysplasia: No significant association between atypia/dysplasia and recurrence or malignant transformation has been found; these cases may still be treated endoscopically 2
• Bilateral disease: Extremely rare but requires bilateral complete resection with same principles applied 6
• Grade heterogeneity: Grade by the highest grade component present; consider clinical parameters (focality, prior diagnoses, size, recurrence frequency, concurrent CIS) when cases are equivocal 1