SEBACEOUS CYSTS (EPIDERMOID CYSTS/PILAR CYSTS)
These are lumps under the skin. Occasionally one can find a small punctum on the overlying skin. The cyst is lined by wall and it contains white cheesy material. Common sites include the body and scalp. The can be more than one present.
The cyst will enlarge with time. Sometimes, the lining will burst. This will lead to an inflammation in the surrounding tissue and overlying skin. This is often mistaken for an infection and treated with antibiotics.
Local anaesthesia(LA) is injected around the cyst. (care is taken as sometimes the LA can squirt out of the punctum and hit the face of the doctor/nurse!)
An incision is made over the skin(usually I make as short an incision as possible). The cyst wall is carefully dissected(often best with an artery forceps) and the cyst wall removed with its contents.
The wound is closed with sutures - usually non-absorbable.
These are left in for 7-14 days. A waterproof dressing is usually used to cover the wound unless on the scalp.
Risks of Surgery
1. Wound problems - scarring, infection, breakdown, pain in scar/reflex sympathetic dystrophy, nerve damage/numbness
2. Recurrence - sometimes a fragment of the cyst wall is stuck down in the surrounding scar tissue and the cyst may regrow.
1. There is usually no need to shave the hair around the cyst if it is on the scalp
2. When infected, it can be difficult to excise the cyst wall completely as local anaesthesia does not work as well. In this situation, it might sometimes be best to drain the pus first and come back for further surgery when the inflammation has settled down.
3. LA - it is often useful to use more. In addition to providing anaesthesia, the LA helps to dissect the cyst wall from the surrounding tissue allowing complete removal of the cyst wall in one piece. The adrenaline and the pressure effect of the fluid helps control bleeding as well.
4. Multiple cysts (eg on the scalp) can be excised in the same session - usually up to 3-4 depending on the sizes.
Note: Mr LP Cheah is an expert in excising sebaceous cysts and lipomas. He sees a large number of such cases in his rooms. He also lectures on excision of sebaceous cysts and lipomas at the Minor Surgical Skills courses at the Royal Australasian College of Surgeons.