If there is a hard bump behind the ear, it is recommended that the patient go to the ENT department to improve the local examination, and also to improve the ultrasound, CT and other related examinations for judgment. There may be the following diseases that can lead to this condition: 1. Lymphadenitis behind the ear, which is the most common. Lymphadenitis can be an inflammatory infection of the ear, parotid gland or other parts of the body, leading to enlarged lymph nodes. 2. Sebaceous cysts behind the ear, which are also more common, are mainly due to sebaceous cysts formed when the secretion of the sebaceous gland is blocked and secretions accumulate, leading to the enlargement of the cystic epithelium. 3. Some patients have Some patients have lymphatic tuberculosis, which can also manifest as a hard bump behind the ear. 4. Some patients have metastatic cancer behind the ear, which is commonly associated with middle ear cancer, parotid cancer, and even nasopharyngeal cancer, which can lead to lymph node cancer metastasis behind the ear. 5. Some patients have osteoma of the mastoid process behind the ear, which can manifest as a hard bump in the mastoid process due to abnormal growth of the osteoma, and can be clearly determined by CT examination. 6, Some patients have lipoma behind the ear, which may also appear, and it is not difficult to judge by ultrasound examination. 7. Some patients have lymphoma of the whole body, which may also appear as lymphoma distribution in the neck and behind the ear.