There is a lump below the root of the ear, and the possible clinical causes are parotid gland swelling, sebaceous cyst, enlarged lymph nodes and so on. 1 Parotid gland mass: below the root of the ear centered on the earlobe, the anterior lower part is mostly benign lesions of the parotid gland, mostly mixed tumors of the parotid gland. There is also a part of malignant tumor of parotid gland. 2. Sebaceous cyst: the secretion of local sebaceous glands of the skin behind the ear is obstructed, and the content gradually accumulates and swells to form a retention cyst. 3. Enlarged lymph nodes: this condition is related to bacterial infection or inflammatory stimulation of neighboring tissues. Bacterial infection around and in the ear may cause inflammation and enlargement of lymph nodes. If the lump persists or is accompanied by obvious pain symptoms, it is recommended to seek medical attention and targeted treatment at the otolaryngology department of the hospital.