Epidermoid cysts belong to the category of body surface tumors, congenital epidermoid cysts are mostly cysts formed by ectodermal cells left in tissues during embryonic development, which can occur on the outer edge of the eyebrows, nose, floor of the mouth, intracranial, neck, clavicle, scrotum, perineum, sacral tail, etc., and can be combined with local dermal sinus, cremasteric fissure, subcutaneous lipoma, etc., and are most common in adolescent patients; acquired factors may be due to trauma to the skin. When the skin is ruptured, some epidermal tissue fragments are implanted in the subcutaneous tissue with external force or foreign body puncture and continue to proliferate and grow, mostly in the fingertips, palms, foot and plantar or surgical wounds, and more common in adults. Epidermoid cysts in the sacrococcygeal region are relatively rare. The early stage of the disease is mostly asymptomatic, so it is not easy to diagnose. When the tumor enlarges significantly and invades or compresses the anal sphincter and rectum, it may manifest as perianal or perineal swelling or vague pain or perianal fistula, however, because these symptoms resemble the manifestations of perianal diseases, it is often misdiagnosed as perianal diseases, especially sebaceous cysts and lipomas. CT can determine whether the cyst invades the surrounding organs. Epidermoid cysts in the sacrococcygeal region need to be differentiated from teratomas, rectal smooth muscle tumors, sebaceous cysts, sebaceous adenomas, and lipomas. Teratomas and rectal smooth muscle tumors appear as heterogeneous densities on ultrasound and CT. Dermatomal cysts are often round, and when combined with intracapsular infection, the intracapsular density is more irregular, and the cyst wall and cyst contents are more enhanced on enhanced scans. Epidermoid cysts, sebaceous adenomas and lipomas are mostly identified by pathological examination. In most cases, epidermoid cysts are treated by excisional surgery, which removes the cyst completely. During the operation, careful peeling is required to prevent rupture; otherwise, if the cyst wall remains, it is easy to recur. Because of the large surgical invasion, nerve damage should be avoided as much as possible, and hemostasis should be thoroughly stopped. The wound cavity should be intermittently sutured under the skin to avoid the formation of dead cavity after surgery, and drainage can be applied to prevent the accumulation of exudate, and antibiotics should be used at the same time to prevent the infection of the incision. If the cyst is large in size, local depression or bone defect after removal, soft tissue graft filling or bone graft repair should be performed at the same time to maintain the normal form.