If the lymph nodes under the jaw are enlarged and hard like eggs, it can basically exclude the lymph node hyperplasia caused by lymphadenitis or connective tissue disease, which may be caused by lymphoma or metastasis of malignant tumor. 1. Lymphoma: when submandibular lymph node area suffers from lymphoma, with the increase of tumor volume, it will lead to subcutaneous lumps, and after lymphatic area is invaded by cancer cells, it will also cause the symptom of submandibular lymph node enlargement as hard as egg. 2. Metastasis of malignant tumors: when lung cancer, breast cancer, oral nasopharyngeal cancer, stomach cancer, liver cancer and other malignant tumors can be metastasized through lymphatic metastasis, resulting in enlarged submandibular lymph nodes, which will also have the symptom of hardness of enlarged lymph nodes like eggs. Patients with enlarged submandibular lymph nodes as hard as eggs should go to the hospital in time, complete the examination, and follow the doctor’s instruction to choose the appropriate method of treatment after clear diagnosis.