“Deep Extrinsic Muscle Involvement” Is a Fallacy in the American Joint Committee on Cancer's Seventh Edition of Tumor Staging of Oral Cavity Cancers

The extrinsic muscles of the tongue are not deep. Even superficial thin tumors can involve these muscles. The eighth edition of tumor staging by the AJCC, which includes tumor thickness in the staging system, is in the process of being implemented. The present study justifies the removal of extrinsic muscle involvement in defining stage T4 of the oral cavity.