Prognostic impact of extratumoral perineural invasion in patients with oral cavity squamous cell carcinoma

Abstract Purpose Perineural invasion (PNI) is an adverse prognostic factor in patients with oral cavity squamous cell carcinoma (OCSCC). The American Joint Committee on Cancer Staging Manual, eighth edition, introduced a subdivision of PNI into two distinct forms, that is, extratumoral and intratumoral PNI (EPNI and IPNI, respectively). We designed the current study to assess whether EPNI and IPNI have different prognostic implications in terms of disease control and survival outcomes in patients with OCSCC. Materials and methods We retrospectively examined 229 consecutive patients with OCSCC and PNI who underwent radical surgery between July 2003 and November 2016. EPNI and IPNI were identified in 76 and 153 patients, respectively. The 5‐year locoregional control (LRC), distant metastasis, disease‐free survival (DFS), and overall survival (OS) rates served as the main outcome measures. Results Compared with patients showing IPNI, those with EPNI had a higher prevalence of worst pattern of invasion type‐5 (P