Prognostic Effect of a Tumor Invasion Pattern Mimicking Crawling Between Muscle Fibers in Oral Tongue Carcinoma

Abstract Purpose 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 Broadening Amoeboid Behavior of Advancing tumor cells (BABA), characterized by an invasive tumor front where cancer cells progress between muscle fibers in an amoeboid manner. Furthermore, we investigated its prognostic significance in oral tongue carcinoma. Methods This retrospective cohort study enrolled patients with oral tongue carcinoma who were referred to the National Cancer Center Hospital East Japan between January 2011 and December 2017. Herein, 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 BABA, were calculated and compared. Results Herein, 211 patients were included, with a median follow-up duration of 4.8 years. Patients with BABA exhibited 2-year overall and recurrence-free survival rates of 78% (p = 0.02) and 39% (p < 0.001), respectively. In multivariable analysis, lymphatic invasion, venous invasion, BABA, and nodal metastasis were strong prognostic factors for recurrence, 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. Conclusion The new pathological feature, BABA, is a potent prognostic factor for oral tongue squamous cell carcinoma recurrence.