Sebaceous and dermoid cysts

When the mouth of a sebaceous gland is blocked, retained sebum causes it to form a cyst. Sebaceous cysts are most common on the face, scalp and back, as hemispherical firm or elastic swellings, with no obvious edge, which are adherent to the skin. They are filled with putty-like yellowish white sebum, which you may be able to indent with your finger.

Three complications may follow: (1) A sebaceous cyst can become infected; this makes it enlarge and become red and painful. Recurrent infection makes it adhere to the surrounding tissue, and become more difficult to remove. (2) It can ulcerate, and discharge its contents. The lining membrane which is left can then resemble an epithelioma. (3) Its contents can escape, and become hard and form a sebaceous horn.

Fig. 34-7 REMOVING A SEBACEOUS CYST. A, excising an ellipse of skin. B, inserting curved scissors to define the plane of cleavage. C, isolating the cyst. D, excising it. F, the incision closed with a drain in place.

SEBACEOUS CYSTS. Paint, drape, and if necessary shave the area.

Under local anaesthesia (A 5.4), incise an ellipse of skin over the swelling, in the direction of the natural lines of the skin. This is particularly important in the face, see Fig. 61-3. Deepen the incision until you reach the edge of the cyst. Push the points of fine curved scissors between the cyst and the tissue round it, and then open them, so as to define a plane for dissection. Repeat this all round the cyst until it is free, then remove it with a snip of the scissors.

Press firmly with dry gauze for 5 minutes to stop bleeding. If any bleeding vessels remain, tie them off. Close the skin, leaving a small corrugated drain in place. Remove this at 48 hours.

DERMOID CYSTS. Lumps very like sebaceous cysts from at the lines of skin fusion in the embryo, most commonly at the lateral end of the eyebrow where the maxillary and ophthalmic divisions of the face meet. Manage them as for sebaceous cysts.