Toratani S, et al. - Researchers classified the local failure (LF) of squamous cell carcinoma of the oral cavity (OSCC) into three clinical types: deep recurrence (type 1R), adjacent superficial recurrence (type 2R), and distant primary tumour (type 3R). They analyzed the LF after surgical resection of OSCC to determine the validity and usefulness of this classification system. Rarely, type 1R developed more than 1 year after surgery, whereas type 2R did not develop within 2 years. Residual cancer cells in the deep margins cause the type 1R, and precancerous cells remaining in the marginal epithelium and gradually becoming invasive cancer cause type 2R. Findings suggested a probability of considering type 3R as an independent tumour. They noted the convenience of the newly proposed clinical classification and this classification roughly reflects the causes and mechanisms of relapse.