Prognostic effect of a tumor invasion pattern mimicking crawling between muscle fibers in oral tongue squamous cell carcinoma

The Union for International Cancer Control classification can predict the outcome of patients with oral tongue squamous cell carcinoma, which has a poor prognosis. However, in some cases, cancer relapse occurs earlier than in others despite an identical stage. Pathological findings are the first step in detecting features associated with a high risk of recurrence. Herein, we identified a novel pathological feature, termed Crawling Amoeboid Migration (CAM), characterized by an invasive tumor front in which cancer cells progress between muscle fibers in an amoeboid manner. Furthermore, we investigated its prognostic significance in oral tongue squamous cell carcinoma (OTSCC). This retrospective cohort study enrolled patients with OTSCC who were referred to the National Cancer Center Hospital East Japan between January 2011 and December 2017. The main pathological features were reevaluated by two investigators who were blinded to the clinical data. Additionally, recurrence-free survival rates according to pathological features, including CAM, were calculated and compared. Herein, 211 patients were included, with a median follow-up duration of 4.8 years. Overall survival and recurrence-free survival were significantly worse in the CAM-positive group than in the CAM-negative group ( p < 0.01 for both). In multivariable analysis, lymphatic invasion, venous invasion, CAM, and nodal metastasis were strong prognostic factors for recurrence-free survival, with hazard ratios (95% confidence intervals) of 2.1 (1.2–3.6), 2.0 (1.1–3.4), 2.2 (1.3–3.7), and 2.0 (1.2–3.6), respectively. CAM is a potent prognostic factor for recurrence-free survival in OTSCC.