The most common form of treatment of a malignant skin tumour is excision, a process which involves removing the entire skin lesion. In certain situations whereby complete excision may not be feasible, other forms of therapy such as cryotherapy, topical therapy (creams), photodynamic therapy (PDT) or radiotherapy may be used.

What is micrographic surgery (MOHS)?

This is a specialised form of skin cancer surgery and is also called Mohs' surgery after the doctor who developed it. Your surgeon first removes the visible portion of your tumour, and then removes a further layer of tissue that may have cancer cells. This tissue is processed in the laboratory and then examined under a microscope while you are still in the dermatology unit. If cancer cells are seen, another layer of tissue is removed and examined. This is repeated until all the cancer cells have been removed.

What happens during MOHS surgery?

There are several stages to Mohs' surgery. First, your doctor will inject the area where your tumour is, with a local anaesthetic. This numbs the area, so you will not feel any pain during surgery. It will not put you to sleep, so you will remain awake throughout the surgery. If you are particularly anxious, we can give you a mild sedative to help you relax. Please discuss this with the doctor. We may also use anaesthetic eye drops if your tumour is near your eye.

Once the anaesthetic has taken effect, the visible (also called the clinically evident) part of the tumour will be removed, along with a small 1-2mm margin of normal skin. The tissue will then be processed and prepared so that your surgeon will be able to look at it under a microscope to check for cancer cells. This takes about 60-75 minutes. A temporary dressing will be applied to your wound and you will be asked to sit in the waiting area.

If cancer cells are present in this tissue, you will be brought back into theatre for more tissue to be cut out and examined under the microscope. This will be repeated until all the tumour cells have been removed.

The local anaesthetic lasts for about 2 hours, and can be 'topped up' if needed. Because of the nature of this surgery, we are unable to tell you exactly how long your surgery will last.

What happens after the MOHS procedure?

Once all the tumour cells have been removed, there are several options for repairing your resulting wound. These will be discussed with you in more detail before your surgery. Your wound may be:

closed by the team who performed the micrographic surgery immediately after the tumour has been removed;
dressed and then repaired by a plastic surgeon at a hospital chosen by our surgeon;
left to heal normally; or
repaired at another hospital. In this case, we will renew your dressing before you travel to your referring hospital. We will also give you a letter from our doctors to hand to your surgeon when you arrive at your referring hospital.

What are the risks of MOHS surgery?

Your doctor will explain the potential risks for this type of surgery with you in more detail, but complications include:

Bleeding at the site of the tumour.
Pain. The local anaesthetic should last until you return home. Aspirin free pain relief (such as Paracetamol) should relieve any discomfort. The doctor or nurse caring for you can give you more advice.
Nerve damage. Although your surgeon will try to avoid this, nerves can occasionally be damaged during surgery, leading to a numb area of skin. This is usually temporary.
Infection at the wound site. You will be given instructions on how to care for your wound to minimise this risk.
Scarring. You will have a scar after the surgery. The doctors use closure techniques to minimise the appearance of this. Scars will fade over time.

What do I need to do after I go home?

Before you leave the hospital, please make sure you have been given information about how to look after your wound at home. You will probably need to rest after the surgery for about 48 hours. If you work, we recommend that you take at least 2 days off after the surgery. We will give you more advice on the day of your surgery.

Will I have a follow-up appointment?

You will have a follow up appointment with the team that repaired your wound. If your follow up is with us at National Skin Centre, we will usually see you one week after your surgery to check that your skin is healing well and to remove any stitches you may have. If there are any changes to this, you will be advised on the day of your surgery. We usually see you again approximately 3 months after your wound has healed.

What is Photodynamic Therapy?

Photodynamic therapy (PDT) is a light-based treatment for certain skin cancers (superficial basal cell carcinoma and Bowen's disease) and precancerous skin lesions due to chronic sun damage (actinic keratosis). This treatment involves the application of a special light-sensitive cream to the affected area where it is taken up by the abnormal cells. The cream is left in place for about 3 hours, following which red light is shone on the treatment area to activate a chemical to kill the abnormal cells.

How is PDT treatment carried out?

On the day of treatment, your doctor will first clear the treatment area of any overlying scales or crust, followed by application of the light-sensitive cream. The cream will be kept in place with an opaque dressing and you will be asked to return to the phototherapy clinic approximately 3 hours after the application. There, the dressing and excess cream will be removed and red light will be shone on the treatment area for between 8 to 20 minutes. In most cases, the same treatment needs to be repeated 1 to 2 weeks later.

What are the side effects of PDT treatment?

During the light treatment, you may experience some burning discomfort where the light is shone, which is mostly tolerable. If necessary, a cold water spray will be administered by the nurse to reduce the discomfort. In cases where pain continues to be an issue, a local anaesthesia injection can be given to numb the treatment area.

Pain and itch may persist following the treatment and this is usually worse in the first 2 days following treatment. The treated area may be reddish or may ulcerate but it rarely leaves a disfiguring scar. A scab may form which usually drops off on its own after a week. Some pigmentation may occur posthealing but this will gradually settle with time. If 2 treatments are unsuccessful, re-treatment may be considered 3 months later.

What do I do after PDT treatment?

You should keep the treatment site covered to avoid sun exposure for 48 hours post-treatment. If a scab forms, be careful not to scratch or peel it off so as not to disrupt the natural healing process. If appropriate, your doctor may prescribe an antiseptic gel to reduce the risk of skin infection at the treated area.