If there is a lump in the neck behind the ear, it may be a sebaceous cyst or an enlarged lymph node, so go to the hospital for an ultrasound to clarify the situation. Sebaceous cysts are usually found around the ears and face and are caused by the accumulation of sebaceous secretions due to blockage of the sebaceous ducts. The initial stage of sebaceous cysts can be no other discomfort, manifested as a local hard swelling, no pain, can slowly grow, usually surgical removal. Once the sebaceous cyst is infected, it can quickly develop into an abscess. Once the abscess is formed, it needs to be incised and drained and the medication changed daily. The common causes of swollen lymph nodes in the neck are lymphadenitis, painless enlargement of lymph nodes or tumor metastasis. It is recommended to go to the hospital in time for examination to clarify the condition and timely treatment.