Most of the masses found behind the ears are caused by enlarged lymph nodes, and a few may be caused by subcutaneous lipomas, sebaceous cysts, dermatomal cysts, hemangiomas, fibromas, and lymphangioleiocysts. Most of the swollen lymph nodes are caused by reactive hyperplasia of lymph nodes due to acute and chronic inflammatory stimuli in the head, face and neck, such as skin and soft tissue infections in the head, face and neck, mastoiditis, otitis media, folliculitis, etc. It can also be caused by dental caries, periodontitis, tonsillitis, and upper respiratory tract infection. A few are caused by lymph node metastasis from malignant tumors of the head, face and neck, such as those of the nasopharynx and thyroid gland, and a few are tumors of the lymph nodes themselves, such as lymphoma, Hodgkin and non-Hodgkin lymphoma.