Sinonasal Papilloma

Epidemiology:

• Adult men

Common sites:

Gross features:

• unilateral
• inverted:
• cerebriform appearance

Histologic features:

• proliferating columnar and / or squamous epithelium
• admixture of mucin-containing cells
• numerous microcysts (microabscesses)
• often many neutrophils in epithelium
• some are entirely composed of oncocytic cells – swollen, granular, eosinophilic
• occasional mitoses in basal layer
• mild to moderate atypia
• orderly maturation pattern
• septal:
• fungiform (mushroom-shaped)
• “villous” architecture with thin central cores of connective tissue
• inverted:
• squamous epithelium
• may have transitional appearance
• arise from lateral wall
• inward growth of epithelium into stroma
• cylindrical:

Immunophenotype:

Marker:	Sensitivity:	Specificity:
HMWK
LMWK

Molecular features:

Other features:

• inverted papilloma is most important due to its uniquely (locally) aggressive behaviour
• tendency to locally recur
• associated with malignancy
• all papillomas have a potential for malignant transformation