Diagnostic Performance of CT/MRI-Based Lymph Node Morphology With Three-Plane Size Measurements in Oral Cavity Cancer

PURPOSE: This study evaluates the diagnostic value of CT/MRI-based nodal morphology and three-plane size criteria for identifying pathologically positive (pN+) cervical lymph nodes (LNs) in oral squamous cell carcinoma (OSCC). METHODS: OSCC patients who underwent neck dissection (2020-2021) were included. Preoperative CT/MRI were reviewed by an observer blinded to clinicopathological information. Visible LNs were assessed for morphologic abnormality and size in short-axial (SAD), maximum-axial (MAD), and craniocaudal (CC) diameters. Sensitivity and specificity of each imaging parameter were calculated using pathology as the reference standard. RESULTS: CT/MRI scans from 148 patients were analyzed. Sensitivity/specificity for detecting pN+ LNs were: 56%/76% (abnormal morphology-alone), 57%/72% (morphology ± SAD >1.0 cm), 83%/28% (morphology ± MAD >1.0 cm), 86%/29% (morphology ± CC >1.0 cm), and 88%/24% (morphology ± any-plane >1.0 cm). Among 64 morphologically abnormal LNs, 25, 6, and 5 measured ≤1.0 cm in SAD, MAD, and CC, respectively, with pN+ rates of 16/25 (64%), 4/6 (66.7%), and 3/5 (60%). In morphologically "normal" (homogenous) LNs, sensitivity/specificity for pN+ detection by >1.0 cm size threshold were: 3%/95% (SAD), 62%/36% (MAD), 68%/39% (CC), and 72%/32% (any plane). CONCLUSIONS: Abnormal LN morphology is the most reliable CT/MRI indicator of pN+ disease in OSCC, irrespective of nodal size, although sensitivity remains modest. In morphologically normal LNs, three-plane size assessment, particularly MAD and CC, improves detection of pN+ beyond SAD. These findings support a morphology-first approach to CT/MRI nodal evaluation and inform an exploratory OSCC-specific decision framework incorporating morphology, multi-plane size assessment, and lymphatic drainage patterns.