A sebaceous cyst will develop under the skin and is a lump behind the ear that is noncancerous, it is generally not harmful but many clients find their sebaceous cyst to be unsightly and in some cases uncomfortable. Although more commonly found behind the ear, some clients will have one on the head, the back, breast or on other parts of the body. Here at LMKskin Laura would recommend that the cyst is removed by surgical excision, which will permanently remove the cyst in one treatment.