Article Humans Longitudinal Studies Lymph Nodes Lymphatic Metastasis Morbidity Mouth Neoplasms Mouth neoplasms Neck Dissection Neck dissection Neoplasm Staging Quality of Life Quality of life Sentinel Lymph Node Biopsy Sentinel lymph node biopsy Shoulder Shoulder function adult cancer staging cohort analysis comparative study elective surgery female human human tissue longitudinal study lymph node lymph node metastasis major clinical study male