The prevalence of lymph node metastases in clinically N0 necks with oral cavity squamous cell carcinoma: is CT good enough for nodal staging?

Background: Nodal metastases and extracapsular extension (ECE) are important prognostic indicators. However, the diagnostic accuracy of CT is still limited for patients with clinically N0 neck. Purpose: To determine the prevalence of lymph node (LN) metastases and ECE for oral cavity squamous cell carcinoma (SCC) patients with clinical and CT negative preoperative neck. Material and Methods: Thirty-two patients with N0 oral cavity SCC who underwent neck dissection were included in this retrospective analysis. The size of LN was measured on transverse CT images, and radiological size criterion was based upon a minimal axial diameter of 10 mm. Pathology was used as the standard reference. Imaging and histopathological correlation was done for 132 LN levels in the 32 patients. Results: Fourteen of 32 patients (44%) had metastatic nodes and six patients had ECE. Among 132 LN levels, 22 levels (17%) had metastatic LNs (level I 5/37, level II 8/39, level III 7/35, level IV 2/18), and eight of 22 levels with metastases had ECE. Poorly differentiated histology was a predictive factor for LN metastases or ECE (poorly versus well and moderately differentiated SCC: P = 0.07 for LN metastases and P = 0.08 for ECE, respectively). T-classification was also an important predictor for occult nodal metastases (2 of 10 patients in T1, 12 of 22 patients in T2-4), although it did not reach statistical significance (P = 0.11). Conclusion: Diagnostic accuracy of CT is limited among N0 oral cavity SCC patients. Neck dissection should be performed, particularly for patients with poorly differentiated SCC or higher T-classification.