There is a small lump behind the ear, which is mainly seen in three kinds of diseases clinically, as follows: first, the more common is lipoma, generally speaking, the exact cause of lipoma is not clear, and it can be long-term without obvious enlargement. For lipoma diagnosis is clear, through ultrasound examination, using local anesthesia complete excision can be cured. Secondly, sebaceous cysts are mainly seen in sebaceous cysts. Generally speaking, sebaceous cysts usually have blackheads on the surface, which can be clearly diagnosed through ultrasound examination. As sebaceous cysts are prone to secondary bacterial infections and even abscesses, they can be cured by complete excision under local anesthesia. Thirdly, it is mainly seen in oral respiratory tract infection caused by postauricular lymphadenitis, generally speaking, it can be manifested as if combined with oral respiratory tract disease, there is postauricular lymph node enlargement, and even accompanied by local pain. In most cases, after anti-infective and anti-viral treatment, the lymph node enlargement can be reduced or even disappear after the symptoms of the primary infectious disease are controlled.