Perineural invasion predicts poor survival and cervical lymph node metastasis in oral squamous cell carcinoma

Background: Oral squamous cell carcinoma (OSCC) usually invades peripheral nerves through a process known as perineural invasion (PNI), recognized as an adverse factor considered for the administration of postoperative adjuvant therapy. The aim of this study was to assess the impact of PNI on survival and cervical lymph node metastasis in a cohort of OSCC patients. Material and Methods: Presence, location and extension of PNI were assessed in a cohort of 57 paraffin-embedded OSCC resections. Clinico-pathological variables were obtained from each case. Five-year overall survival (OS) and 5-year disease-specific survival (DSS) curves were constructed according to the Kaplan-Meier method and compared with log-rank test. The Cox proportional hazard model was used to assess the role of PNI as an independent risk factor related to poor survival, and a binary logistic regression was performed to estimate the predictive value of PNI for regional lymph node metastasis. Results: PNI was observed in 49.1% of the cases, affecting only small nerves. Peritumoral PNI was the most common location, and multifocal PNI the most frequent extent. Most PNI positive cases had cervical metastasis (p=0.001), and PNI was more frequent in stages III-IV than in I-II (p=0.02). The five-year OS and the 5-year DSS decreased in PNI positive and peritumoral PNI cases. PNI was an independent risk factor for poor 5-year OS and poor 5-year DSS. The odds for cervical lymph node metastasis were of 6.076 (p=0.006) and 10.257 (p=0.007) for PNI and Tumor budding (TB) positive cases, respectively. Conclusions: PNI is a frequent finding in OSCC and an independent risk factor for poor OS and DSS. PNI and TB are both risk factors associated to an increased likelihood for the development of lymph node metastasis. Therefore, we suggest further investigations to test the combined PNI-TB scoring system in risk stratification models for OSCC.