xRead - Nasal Obstruction (September 2024) Full Articles

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KUANetal.

TABLE XVI.1 Summary table on different types of sinonasal papilloma. Rates of malignant transformation Molecular mutations

Dysplasia predisposing to malignancy

Association with HPV

Inverted

5%–15%

EGFR

Association noted

Low-risk HPV may present in some patients and may play a role in tumor development, but not consistent in all patients Strong association with low-risk HPV Weak to no association with HPV

Exophytic

Rare

Unknown

Rarely seen

Oncocytic

4%–17%

KRAS

Association noted

clinical behavior patterns can make the diagnosis diffi cult at times (Table XVI.1). Furthermore, certain tumors possess the ability to progress to malignancy. Advances in immunohistologic and molecular analysis have gen erated much interest in the investigation of factors that drive tumor progression. Specific areas of concern include the role of HPV, both high-risk and low-risk strains, and somatic genomic mutations. In this section, we summarize the current literature pertaining to sinonasal papilloma subtypes (inverted, exophytic, and oncocytic), explore the association of HPV to these papillomas, and evaluate factors leading to malignant conversion. A Exophytic papilloma Exophytic papillomas are the second most common sinonasal papilloma type, representing 10%–33% of all sinonasal papillomatous disease. 643–645 These tend to occur in younger patients between the second and fifth decade of life and have a 2–3:1 predilection for male patients. 645–648 The nasal septum appears to be the most common site of anatomic involvement. 643 Although there is a propensity to recur, exophytic papilloma rarely undergo malignant transformation and have improved prognosis compared to other papilloma subtypes. 644,649–653 Histologically, exophytic papilloma is distinct from IP due to its predominantly exophytic growth pattern, lack of transmigrating intraepithelial neutrophilic inflammation, and frequent presence of overlying keratosis. 643,646 Low risk HPV—in particular, types 6 and 11—has a strong association with this disease process, with many studies reporting over 70% positivity rate. 95,643,646,654–657 B Oncocytic papilloma Oncocytic sinonasal papilloma is the least common sub type of sinonasal papilloma (about 6%) with no appar ent predilection for sex. 643,645–647 Clinically, these tumors are similar to IP, based on anatomic location (i.e., fre

quent involvement of the paranasal sinuses), overall prognosis, and risk of malignant transformation (approx imately 4%–17%). 645–647 Histologically, oncocytic papillo mas are distinct from IPs due to their frequent combined endophytic and exophytic growth patterns, predominant cuboidal to columnar cell morphology with eosinophilic cytoplasm, and prominent intraepithelial neutrophilic microabscesses. 36,643,646 Oncocytic papilloma is also dif ferent from IP due to the absence of somatic EGFR mutations and presence of highly prevalent somatic KRAS mutations. 643,658 Additionally, there is infrequent associa tion with HPV in oncocytic sinonasal papilloma. Regard less, the risk of malignant degeneration is similar to that of IP, warranting a similar treatment approach. C Inverted papilloma IP is the most common sinonasal papilloma subtype, repre senting 62%–78% of cases and, as such, data for IP dominate the literature. 645–647 Usually these tumors occur along the lateral nasal wall or arise from within the paranasal sinuses. Histologically, IP has a characteristic appearance: it is composed predominantly of immature squamous cells with a classic “ribbon-like” endophytic (inverted) growth pattern and pathognomonic transmigrating intraepithe lial neutrophilic inflammation. 643,646 Somatic mutations in the epidermal growth factor receptor ( EGFR ) gene are present in the majority of IP. 658,659 Low-risk HPV (types 6 and 11) is common in IP and is presumed to play a role in tumorigenesis. 658,659 Indeed, recent data indicate that these are mutually exclusive processes driving tumorigen esis, in that IP is either driven by low-risk HPV or somatic EGFR mutations. D Dysplasia and risk of malignant transformation Malignant transformation of sinonasal papilloma is a major source of morbidity and mortality