Inverted Schneiderian papilloma

Inverted sinonasal or Schneiderian papilloma shows endophytic or “inverted” growth pattern (top left). These nests of squamous epithelial cells grow down into the myxomatous to fibrous stroma with chronic  inflammatory cells and vascularity (top right and bottom left).  Epithelial component shows many clear cells suggestive of glycogen presence, and maintains polarity and nuclear uniformity (bottom right).

Papillomas are benign neoplasm arising from the sinonasal or Schneiderian mucosa. Squamous or columnar epithelial proliferations characterize these lesions. They are categorized into: 1) septal 2) inverted or 3) cylindrical. Septal and inverted papillomas are the most common – each comprising of about ~45-50% of all papillomas. They are rarely seen in pediatric population, but septal papillomas tend to occur in younger age group (20-50s). Patients typically present with unilateral nasal obstruction, epistaxis, and pain. The etiology remains unclear, but HPV types 6/11 have been implicated in the pathogenesis. Malignant transformation occurs in about 10% of inverted and cylindrical papilloma. However, the propensity for malignant transformation is rare with septal papilloma. Treatment is complete surgical excision of the mass with negative margins. Lateral rhinotomy or medial maxillectomy may be performed to ensure complete resection of the tumor. Incomplete removal of the lesion results in recurrence of the tumor with potential invasion of surrounding tissue. Other complications include malignant transformation.