Sinonasal undifferentiated carcinoma (SNUC) is distinguished from other high-grade sinonasal malignancies by all of the following features EXCEPT:

• A Origin from the sinonasal Schneiderian epithelium
• B Absence of squamous or glandular differentiation on histology
• C Aggressive behaviour with frequent skull base invasion at presentation
• D Uniformly positive staining for HPV high-risk types (p16 overexpression) ✓

Explanation

SNUC is a high-grade, poorly differentiated carcinoma of unclear histogenesis with no evidence of squamous, glandular, or neuroendocrine differentiation. It is characterised by aggressive local invasion and early regional/distant metastasis. Unlike HPV-associated oropharyngeal SCC and a subset of sinonasal SCCs, SNUC is NOT uniformly p16/HPV-positive; p16 positivity, when present, may reflect pathway dysregulation rather than HPV aetiology. Diagnosis requires exclusion of lymphoepithelioma (EBV-related), olfactory neuroblastoma (synaptophysin+), NEC, and rhabdomyosarcoma.

Reference: Dhingra Diseases of Ear, Nose and Throat, 7th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.