Sebaceous cysts are common, present with a very benign evolution, may be located anywhere on the body, and frequently become infected. They are most commonly found on the face, neck, and trunk. Sebaceous cysts are usually asymptomatic unless they become infected, cause compression, or cause a deformity over sensitive areas of the body (Figure 136-1). The Emergency Physician must be acquainted with treating infected sebaceous cysts, particularly if they are located on cosmetically important areas such as the face.
An example of an infected sebaceous cyst located on the posterior neck. (Used from Steven Fruitsmack, www.commons.wikimedia.org.)
ANATOMY AND PATHOPHYSIOLOGY
Sebaceous cysts are the result of obstruction of sebaceous gland ducts. They are freely mobile, slow growing, round shaped, painless, and located in the subcutaneous tissues.1 The cysts are made of a thin white capsule filled with a thick, cheesy, and keratinous material. Their size is variable and ranges from less than a quarter of an inch to more than 2 inches. These keratin-containing lesions are usually seen in young and middle-aged adults in relation to a pilosebaceous follicle.2 Sebaceous cysts may be present for many years before infection occurs. Physical examination often reveals a subcutaneous mass that is fluctuant and tender (Figure 136-1). The overlying skin may appear normal or erythematous.
The initial treatment of choice of an infected sebaceous cyst is incision and drainage. The sebaceous material is too thick to allow for spontaneous drainage and it must be expressed. The sebaceous cyst will likely recur unless the capsule of the cyst is removed. Patients may have the initial incision and drainage performed in the Emergency Department with follow-up at some later date to remove the cyst capsule. Alternatively, the cyst capsule may be removed at the time of the initial incision and drainage (Figure 136-2).
The removed sebaceous cyst. Note that it is enclosed in a connective tissue capsule. (Used from Steven Fruitsmack, www.commons.wikimedia.org.)
Ultrasound is a useful tool for the diagnosis of a sebaceous cyst.3-5 It allows for the differential between it and its mimics (e.g., cutaneous masses, hernia, lipoma, lymph node, subcutaneous malignancies, or a vascular abnormality). It can be difficult to distinguish between a sebaceous cyst and another entity. A sebaceous cyst may appear as a small, well-defined, and superficial mass. The inside appearance can vary with the contents.
Incision and drainage in the Emergency Department is indicated whenever a patient presents with a tender sebaceous cyst consistent with an abscess. The procedure will relieve the patient’s pain. Antibiotics without drainage are ineffective in treating abscesses.6 The ...