Lymph nodes behind the ear can be either primary lymphoma or metastatic lymph node cancer metastasized from tumors elsewhere. In either case, the chance of occurrence is very low because the lymph nodes in the area behind the ear, in the vast majority of cases, form enlargements that are generally reactive hyperplasia caused by local infections. From upper respiratory tract infections to rhinitis, or local skin infections, infectious mononucleosis, etc., all may cause painless enlargement of the lymph nodes in this area. If it is caused by a malignant tumor, as I said earlier, it is very rare and basically unlikely that malignant tumors will appear in this location, but it is not absolutely absent. There are reports of Hodgkin’s lymphoma, which starts in the lymph nodes behind the ear and then spreads to the neck. Another part is like nasopharyngeal carcinoma or other local head and neck tumors, such as sinus carcinoma, which has localized lymph node metastasis, but it usually metastasizes to the neck, not to the lymph nodes behind the ear. In general, the lymph nodes behind the ear are not likely to have malignant tumors. If this is really considered, a puncture biopsy under ultrasonography should be done to clarify what the lesion is.