Mohs surgery

picture of mohs surgery microscope

Mohs surgery

Mohs surgery is often called the ‘gold standard’ for excision of some skin cancers

What is Mohs Surgery?

Mohs surgery (also called Mohs Micrographic Surgery) is named after Dr Mohs, who founded and described the technique of Mohs surgery in the 1930s.

Mohs surgery, unlike ‘conventional surgery’, performs the laboratory tests on the same day as removal of skin cancers such as basal cell carcinoma. This results in a higher cure rate, and is often seen as the ‘gold standard’ treatment of choice for a number of skin cancers, especially basal cell carcinomas

How is Mohs Surgery performed?

Mohs surgery is usually performed under local anaesthetic (an injection is used to numb the skin around the cancer),  but if needed can be under general anaesthetic (with you asleep). The skin cancer is then removed, but unlike conventional surgery for basal cell carcinoma where a wide margin of skin is taken, only a minimal margin of ‘normal looking’ skin is initially taken in Mohs surgery.

The wound is then dressed with a sterile dressing and you return to the ward area. The Mohs surgeon takes the skin specimen into the nearby Mohs lab and processes it to produce slides that can then be checked under a microscope. Mohs maps have also been drawn of where the skin cancer came from.

When the slides are checked, the Mohs surgeon is looking for any evidence of skin cancer that hasn’t been fully removed (skin cancers can have extensions, like roots, that can extend far away from the main cancer, but are not visible by naked eye from the outside of the skin – the only way to see these ‘roots’ is with the microscope). If any is found, then the location can be drawn on the map. The Mohs surgeon can then tell whereabouts on the wound the skin cancer might be.

The skin is then numbed again, and a further thin layer is removed, but only from where the remaining skin cancer ‘roots’ are. The wound is dressed, slides processed and checked, and the process is repeated until the skin cancer has been cleared.

The wound can then be repaired which, depending on the location, size and shape of the wound, may need various reconstructive techniques. These include simple closure (stitching of the wound), moving in skin from nearby (local flap), skin grafting, or even more complex techniques. Occasionally, the wound may be left to heal on its’ own, if it is the right size, shape and location for this.

Often, as the reconstruction is such an important part of the surgery, it is common for a Mohs surgeon to send you to a specialist in Reconstructive surgery, with the reconstruction taking place 1-2 days after the Mohs surgery. Sometimes a Mohs surgeon will be able to reconstruct the wound themselves though, and so can usually perform the reconstruction for you on the same day as your Mohs surgery.

What are the advantages of Mohs surgery?

When the slides are checked in Mohs surgery, the entire skin edge and deep margin are checked, unlike in ‘conventional surgery’ where only a small proportion of the edges are seen. This way, every part of the skin cancer can be chased out, which for basal cell carcinoma gives a 5-year cure rate of 99% with Mohs surgery (as opposed to 90-95% for conventional surgery).

Also, in the case of basal cell carcinoma, conventional surgery usually takes away at least a 3-4mm margin of ‘normal looking’ skin with the tumour in case any ‘roots’ are present. In Mohs surgery though, only the tissue with basal cell carcinoma is removed. This means that, often, more healthy skin is kept and the wound may be smaller than with conventional surgery. This can result in smaller scars, or even change the reconstruction needed.
Due to these advantages, Mohs surgery has become known as the ‘gold standard’ for treatment of a number of different skin cancers, especially basal cell carcinoma

This information is for general information only. If you have any concerns about your health or are considering any treatments, you should seek advice from a healthcare specialist

Other Skincare articles

Learn about these commonly missed cancers that can be treated with Mohs surgery

These cancers don’t always start as moles – read more here

Some skin growths can be shaved or scraped away……