Prognostic significance of the neural invasion in oral squamous cell carcinoma.

BACKGROUND: Although nerve involvement can predict recurrence and prognosis in oral squamous cell carcinomas (OSCC), there still have controversies and limitations regarding the standardization for its detection. In this study we explore the impact of neural invasion in OSCC prognosis, comparing intraneural invasion (INI, tumor cells inside nerve structure) and perineural invasion (PNI, cells involving the nerve, but not invading its sheath).

METHODS: Surgical slides stained with hematoxylin and eosin from 235 patients with OSCC were carefully verified for the presence of INI and PNI. The location in the tumor (intratumoral versus peritumoral) and number of foci (unifocal or multifocal) were also explored. Survival analyses for cancer-specific survival (CSS) and disease-free survival (DFS) were performed with Cox proportional model.

RESULTS: Neural invasion was identified in 74 cases, 64.9% displayed INI and 35.1% displayed PNI. Univariate analysis revealed a significantly poorer CSS, but not DFS, in patients with INI, in contrast to cases with PNI that did not achieve significant association with both CSS and DFS. Further analyses revealed that the location in the tumor and number of foci had little impact on discriminatory ability of INI. Multivariate analysis confirmed that INI is significantly and independently associated with poor CSS (HR: 2.50, 95% CI: 1.31-3.79, p=0.003).

CONCLUSION: This study provides evidence that INI, but not PNI, is a relevant predictor of survival in patients with OSCC, suggesting that its association with other clinical and pathological prognostic factors should be consider in determining the optimal treatment protocol and prognosis of these patients.