A surgical technique used to remove the two most common forms of skin cancer (basal cell and squamous cell carcinomas), and some cases of melanoma as well. Mohs surgery involves the removal of the cancerous tumour, leaving healthy tissue intact, and offers the highest recovery rates of any technique, even for cancers that have been previously treated.
The technique was pioneered by Dr. Frederic E. Mohs in the 1930s. He discovered that he could remove layers of tissue, freeze them, and then map the precise location of the tumour using a microscope to examine the tissue on a cellular level. Over the decades the technique has been perfected by Dr. Mohs and adopted by others, and today the tissue is removed, mapped, and examined under the microscope immediately, so that the surgeon can return to the patient right away to remove any remaining cancer. It is said to be 99% effective in treating non-melanoma skin cancers.
Like many fair-skinned people who grew up before the era of "sun sense", I developed a basal cell cancer on my nose (they almost always occur on the face, neck, or hands). The initial standard treatment involved local freezing and surgical removal of the tumour (basically digging it out with a knife); a biopsy was taken and sent to the lab to confirm the diagnosis of cancer. After the removal the wound was cauterized (sometimes it's closed with a stitch) and I was sent away, to return in three months for follow up. At that time my dermatologist confirmed what I had suspected: the cancer was recurring, spreading around the edges of the scar.
It's not that my dermatologist was incompetent. The problem is that the surgical excision is guided by the human eye, which might not be able to detect the precise boundaries of the tumour, and so it was in my case. She referred me for Mohs surgery, the standard treatment for recurring cancer. Other reasons to have Mohs surgery include cancer in an area where it's important to preserve healthy tissue (e.g. the eyelid), and large, rapidly growing tumours.
The Mohs surgery involved local freezing again, after which the surgeon removed a thin layer of tissue all around the existing scar. I sat for about an hour with a huge piece of gauze on my nose while my sample - and that of four other people having the surgery that day - was microscopically examined. One small area was targetted for a second removal, checked, and then I was sent home. Sometimes the surgeon is also a plastic surgeon and does a "reconstruction" on the spot; I saw a plastic surgeon the next day. He cut a flap of skin from the adjoining area and stitched the whole thing up. It looks a bit gruesome right now - I just had this done two days ago - but he assures me that in a few months it will look much better. I will have a zig zag scar, at which point you can start calling me Zorro or Harry Potter, if you wish.
Find out more about Mohs surgery at http://www.acmmsco.org/AboutMMS.html
Update, January 2006: the wound healed well and is now virtually undetectable, and there has been no recurrence of the cancer. Yay!