DEAR DOCTOR K:
I have basal cell skin cancer on my face and am scheduled to have Mohs surgery. Can you describe what will happen during the procedure?
Skin cancer is the most common cancer in the United States. Basal cell cancer is a very slow-growing type of skin cancer. It is unlikely to spread to other parts of the body, and therefore is rarely life-threatening. The most common cause of basal cell cancer is damage from sun exposure.
Basal cell carcinoma begins in basal cells, which are located deep in the skin. When these basal cells turn cancerous, they invade surrounding tissues, spreading downward and outward below the skin’s surface.
Basal cell cancer occurs most often on the skin near the eyes, nose, lips and ears. That’s because the skin in these areas is most likely to be exposed to sunlight. Basal cell cancers can form elsewhere on the body, as well.
When it starts, the cancer forms a small, smooth, painless white or pink bump. The bump later becomes an open ulcer with a hard edge. (I’ve put an illustration of basal cell skin cancer below.)
Basal cell carcinoma
The cells of this type of cancer resemble the cells in the lowest layer of the epidermis, the basal layer. The cells invade surrounding tissues, forming a painless bump that later becomes an open ulcer with a hard edge.
Mohs micrographic surgery is a specialized procedure that has two main advantages. First, it is better than the traditional technique at seeing the edges (“margins”) of the cancer, thereby assuring the surgeon that all of the cancer has been removed. Second, it gives a better cosmetic result.
Mohs surgery is usually the first choice for removing high-risk basal cell skin cancers. It also is the usual first choice for high-risk cases of a second common type of skin cancer, squamous cell cancer. High-risk cases are those most likely to return. Mohs also is more often the choice when either of these cancers is on the face.
The goal of Mohs surgery is to remove all of the cancer cells while preserving as much of the normal tissue around the cancer as possible. The more normal tissue that is preserved, the smaller the scar and the better the cosmetic result.
The surgery is done in steps. The surgeon shaves away the tumor in thin layers, one layer at a time. Each layer is immediately checked under a microscope. This process is repeated until the outer edge of the removed layer (the margin) is free of cancer cells. This allows the surgeon to preserve as much healthy skin as possible while making sure that all of the cancer is removed.
Mohs surgery is performed under local anesthesia. The procedure typically takes two to four hours. Much of that time is spent waiting while the removed tissue is analyzed, to see if the margin is cancer-free.
The cure rate for basal cell skin cancers with Mohs surgery is close to 100 percent. For the best results, be sure the doctor who performs your Mohs surgery has expertise in the technique. The surgical staff should be trained to process and evaluate each layer of tissue quickly and accurately.