Increased Presence of Perineural Invasion in the Tongue and Floor of the Mouth: Could It Represent a More Aggressive Oral Squamous Cell Carcinoma, or Do Larger Aggressive Tumors Cause Perineural Invasion?

Purpose: Despite data showing worse outcomes and aggressive disease behavior, perineural invasion (PNI) has not been well characterized in terms of tumor location, histopathologic features, or cervical lymph node status. The specific aims of this study were to measure correlations between PNI, tumor location, and other known histopathologic characteristics used to define aggressive disease. Materials and Methods: This was a retrospective cohort study of adult patients with primary squamous cell carcinoma of the oral cavity who underwent neck dissection. We excluded patients whose neck was previously treated with surgery or radiation therapy. Demographic and histopathologic variables of interest were obtained from patient charts. The primary outcome of interest was PNI, and the predictors of interest included tumor location, histopathologic tumor characteristics, and cervical lymph node status. For continuous variables, mean differences were compared by t tests. For categorical variables, the differences in the distribution of the proportions were analyzed with the chi(2) test. All variables were entered simultaneously into a multivariate logistic regression model to control for possible confounding. Statistical significance for the study was set at P < .05. Results: Three hundred sixty-eight patients met the study criteria. PNI showed statistically significant correlations with lymph node status, tumor depth, and specific primary tumor location. PNI was more likely to be seen in tumors located in the tongue or floor of the mouth. Tumors with PNI had a deeper depth of invasion: 15.9 +/- 10.9 mm versus 10.2 +/- 10.0 mm (P < .001). PNI tumors had a higher mean total number of positive nodes: 2.85 +/- 5.23 versus 0.83 +/- 1.80 (P <.001). Conclusions: PNI is statistically correlated with tongue and floor-of-the-mouth subsites within the oral cavity, as well as larger tumors, deeper tumors, and disease that has progressed to the lymph nodes. Whether this correlation represents causation in either direction remains unknown. (C) 2018 American Association of Oral and Maxillofacial Surgeons