A lump at the base of the ear may be related to sebaceous cyst, mixed tumor of parotid gland, enlarged lymph nodes and other causes. 1. Sebaceous cysts: If the excretory ducts of sebaceous glands are blocked, the gradually increasing contents become obstructed, retained and swollen, forming sebaceous cysts. A cyst that occurs under the base of the ear may cause the patient to show a lump under the base of the ear. 2. Mixed tumor of parotid gland: Mixed tumor of parotid gland is a tumor originated from parotid epithelium, containing parotid tissue, mucus and cartilage-like tissue, also known as pleomorphic adenoma of parotid gland. Usually there is no obvious symptom, but the increase of tumor volume can cause local lumps and other manifestations, which may make the patient have a lump under the root of the ear. 3. Enlarged lymph nodes: otitis externa, otitis media and local inflammation of the auricle will lead to enlarged local lymph nodes, which can be manifested as a lump under the root of the ear. When the patient found a lump under the ear, it is recommended to receive examination as soon as possible to identify the cause of the disease, under the guidance of the doctor active treatment.