Mohs surgery

Dr Tshepo Mokwena explains Mohs surgery for skin cancer.

What is Mohs surgery?

Also referred to as Mohs micrographic surgery, it’s a precise surgical technique used to treat different types of skin cancers. 

During Mohs surgery, thin layers of cancer-containing skin are adequately removed, and microscopically examined until only cancer-free tissue remains. 

The principle of Mohs surgery was developed, in 1938, by a general surgeon, Frederic E. Mohs, and the process was modified and perfected with modern technology to date.

The state-of-the-art procedure allows a specialist dermatologist to be a surgeon (Mohs surgeon), a pathologist and a reconstructive surgeon.

The process of Mohs

It involves the removal of cancerous tissue which is then processed by the Mohs surgeon in an on-site Mohs histological laboratory, while the patient returns to the hospital ward or waits in the waiting room. 

This process allows tissue slides to be produced that show the whole, complete cut surface around the tumour, with modern staining or tissue marking techniques to enable orientation, and the exact location of the tumour. 

The slides are then microscopically examined by the Mohs surgeon and any remaining tumour will be indicated very accurately, also including the exact area on the tumour wound where the tumour is still present.

During the process, the patient returns to the day theatre or procedure room where the process is repeated but only on the area of the remaining tumour, leaving the healthy tumour-free area of the wound untouched.

Once the Mohs surgeon confirms the skin and the affected area to be cancer-free, a specialist reconstructive surgeon or the Mohs surgeon will repair the defect where the cancer was removed, almost always on the same day.

Areas that should be treated 

Large skin cancers, skin cancers with more aggressive growth patterns, cancers recurring following previous treatment, incompletely removed skin cancers, or skin cancers involving vital areas, such as nose, ears, lips and eyelids should be treated with Mohs surgery.

For complicated skin cancers, therapy is advanced through a multi-disciplinary team of plastic surgeons, ENT surgeons, oculoplastic, medical oncologists, surgical and radiation oncologists.

Benefits of Mohs surgery

Mohs surgery has been scientifically shown to have the highest success rate, as compared to traditional surgery of wide excision, with healthy wide rim tissue. The old traditional wide excision also resulted in tumour cells being left behind. 

It continues to have the highest cure rate (99,5% for new skin cancers and 95% for recurrent skin cancers), but unfortunately, no cancer treatment or surgery has a 100% cure rate.

It can also be more cost-effective than other surgical methods, when considering the cost of surgical removal and separate histopathological analysis. 

Outcome and healing

This depends on the size of the defect and the reconstructive process undertaken. Factors, such as underlying diseases, may play a role in the outcome. However, bleeding and infections are uncommon. The patient is followed-up for wound care management.