1.Modern zoning criteria of cervical lymph node groups: The cervical lymph nodes are divided into 6 zones. ① Zone Ⅰ (LevelⅠ): including sub-chin lymph node group and sub-mandibular lymph node group. It is further divided into 2 sub-areas, namely ⅠA (sub-chin lymph node group); ⅠB (sub-mandibular lymph node group). ② Zone II (Level II): deep superior cervical lymph node group. It is divided into 2 subzones, bounded by the paraspinal nerve. Zone IIA refers to the deep upper cervical lymph nodes located below the anterior part of the paraspinal nerve; Zone IIB refers to the deep upper cervical lymph nodes located above the posterior part of the paraspinal nerve. ③ Zone Ⅲ (Level Ⅲ): deep middle cervical lymph node group. ④ Zone Ⅳ (Level Ⅳ): deep lower cervical lymph node group. It is divided into 2 subzones: Zone ⅣA is the deep lower cervical lymph nodes behind the clavicular head of the sternocleidomastoid muscle; Zone ⅣB is the deep lower cervical lymph nodes behind the sternal head of the sternocleidomastoid muscle. Zone Ⅴ (Level Ⅴ): the posterior cervical triangle lymph node group (including the paraspinal lymph node group, transverse cervical and supraclavicular lymph node group). It is divided into 2 subzones, with the scapular hyoid muscle as the boundary. Zone VA is the posterior triangular lymph node group above the posterior scapular hyoid muscle, namely the paraspinal lymph node group; Zone VB is the posterior triangular lymph node group below the anterior scapular hyoid muscle, including the transverse cervical and supraclavicular lymph node groups. Zone VI (Level Ⅵ): anterior cervical lymph node group (including larynx, trachea and peri-esophageal lymph nodes). 2. Classification criteria of cervical lymphatic dissection: There are four major categories. (1) Radical cervical lymphatic dissection (RND): the scope of surgical dissection: the upper border of surgery is the lower border of the mandible, the lower border is the clavicle, the anterior border is the midline of the neck, and the posterior border is the anterior border of the trapezius muscle, and the lymphatic tissues and corresponding fatty connective tissues in zones Ⅰ to V are dissected, together with the sternocleidomastoid muscle, the internal jugular vein and the paraneoplastic nerve. (2) Modified radical cervical lymphatic dissection (MRND): The scope of surgical dissection is the same as that of RND, i.e., the lymphatic tissues in regions I-V are dissected, but the sternocleidomastoid muscle, internal jugular vein and paraglottic nerve are preserved, or one or two of the three structures are preserved. MRND-II (MRND with preservation of the paramedian nerve and internal jugular vein); MRND-III (MRND with preservation of the sternocleidomastoid muscle, internal jugular vein and paramedian nerve). (3) Selective cervical lymphatic dissection (SND) ① Supraomohyoid neck dissection (SOND): The lymphatic and corresponding fatty connective tissues in zones I-III are dissected, i.e., the upper border of the operation is the inferior border of the mandible, the posterior border is the posterior border of the sternocleidomastoid muscle, and the anterior lower border is the superior belly of the scaphoid hyoid muscle. ② Lateral neck dissection (LND): Lymphatic and corresponding fatty connective tissues are dissected from II to IV, i.e., the upper border of the operation is the skull base, the lower border is the clavicle, the anterior border is the lateral border of the sternocleidomastoid muscle, and the posterior border is the posterior border of the sternocleidomastoid muscle. Posterolateral neck dissection: The lymph and the corresponding fatty connective tissue in areas II-V are dissected, and the retroauricular lymph nodes and occipital lymph nodes, which are not included in the traditional RND, are often dissected at the same time. Anterior compartment neck dissection: The lymph and the corresponding fatty connective tissue of zone VI are dissected, i.e. the upper border of the operation is the hyoid bone, the lower border is the superior sternal notch, and the two lateral borders are bounded by the common carotid artery. (4) Extended radical neck dissection (ERND): Based on the scope of radical neck lymphatic dissection (i.e., dissection of zones I-V), one or more lymph node groups and/or non-lymphoid structures outside the RND are also removed. For example, lymphatic structures such as the retropharyngeal lymph node group, occipital lymph node group and/or non-lymphatic structures such as the common carotid artery, the hypoglossal nerve, and the vagus nerve are removed for treatment purposes.