Submandibular lymph nodes usually do not easily become cancerous. Swollen submandibular lymph nodes are mostly caused by bacterial infection, which manifests as lymph node inflammation, with redness, swelling and pain on the surface of the lymph nodes, and the lymph nodes will be enlarged and even have pus head formation, which are benign lesions. When thyroid cancer appears in the neck, the lymph nodes around the thyroid gland are swollen and usually there is no pain, mainly the lymph nodes around the thyroid gland, that is, the sixth region, are swollen. Metastasis.