Microscopic description:

Endophytic (inverted) or exophytic growth patterns.

Epithelial lining is pseudostratified and columnar with abundant eosinophilic granular cytoplasm and hyperchromatic uniform nuclei.

Intraepithelial mucin filled cysts with neutrophilic microabscesses may be seen.

Discussion:

Sinonasal papilloma is a benign epithelial neoplasm of sinonasal tract.

WHO has divided sinonasal papilloma into 3 distinct types:

  • Inverted papilloma
  • Exophytic papilloma
  • Oncocytic papilloma

Oncocytic papilloma almost always occurs unilaterally on the lateral nasal wall or in the paranasal sinuses (usually the maxillary or ethmoid).

It may remain localized, involve both areas, or (if neglected) extend into contiguous areas.

Unlike in exophytic and inverted papillomas, HPV has not been identified in oncocytic papillomas.

The clinical behavior parallels that of inverted papilloma. At least 25–35% of cases recur, usually within 5 years.

About 4–17% may harbor a carcinoma.

Most of these are squamous, but mucoepidermoid, small cell, and sinonasal undifferentiated carcinomas have also been described.

Prognosis depends on the histological type, the degree of invasion, and the extent of tumor. In some instances, the carcinoma is in situ and of little consequence to the patient, whereas other cases are locally aggressive and may metastasize.

Positive stains:

  • Cytokeratin AE1 / AE3, CK7, CK5 / 6 (in squamous lining), p40 (in squamous lining)

Negative stains:

  • S100, CD45 and other nonepithelial markers

Table depicting squamous cell carcinomas
References:

WHO Classification of Head and Neck Tumors (WHO Classification of Tumours) 4th Edition

Bishop J. A. (2017). OSPs and ESPs and ISPs, Oh My! An Update on Sinonasal (Schneiderian) Papillomas. Head and neck pathology, 11(3), 269–277. https://doi.org/10.1007/s12105-017-0799-9

CASE IMAGES