Occult cervical nodal metastasis in surgically treated cN0 hypopharyngeal squamous cell carcinoma: prevalence and level-specific distribution in a Vietnamese cohort.

BACKGROUND: Clinically node-negative (cN0) hypopharyngeal squamous cell carcinoma (HPSCC) carries a high risk of occult cervical nodal metastasis, but the data on its prevalence and level-specific distribution remain limited. OBJECTIVES: To determine the prevalence and level-specific distribution of occult cervical nodal metastasis and explore clinicopathological associations with occult nodal disease in surgically treated cN0 HPSCC. MATERIALS AND METHODS: In this retrospective surgical cohort, 28 patients with cN0 HPSCC underwent partial or total pharyngolaryngectomy with neck dissection between January 2020 and March 2026. Occult nodal metastasis was defined as postoperative histopathological pN + disease. Nodal distribution was mapped by neck level, and exploratory clinicopathological associations were examined using univariable Firth logistic regression. RESULTS: Occult cervical nodal metastasis was identified in 11/28 patients (39.3%). Ipsilateral occult metastasis was observed in 10/28 patients (35.7%), with Levels II and III most frequently involved, followed by Level IV. In exploratory univariable analysis, medial wall invasion of the pyriform sinus was associated with occult nodal metastasis (unadjusted OR, 5.52; 95% CI, 1.12-27.30; p = 0.036). CONCLUSIONS AND SIGNIFICANCE: Occult nodal metastasis is common in cN0 HPSCC and predominantly involves ipsilateral Levels II-IV. Medial wall invasion of the pyriform sinus showed an exploratory association with occult nodal metastasis and requires validation in larger prospective cohorts.