Harvard Women's Health Watch

Ask the doctor: What is Mohs surgery?

Q. My dermatologist is recommending Mohs surgery to remove a basal cell cancer on my nose. What does this involve?

A. Mohs micrographic surgery is named after Frederic Mohs, who developed the technique in the 1930s. It's a specialized surgical procedure used to eliminate skin cancers that spread locally (but do not spread through the body) and are likely to return unless all the cancer is cut out. The goal of Mohs surgery is to remove all of the cancer cells while preserving as much of the normal tissue as possible. To do this, the surgeon removes the cancerous tissue layer by layer, examining each layer under a microscope, until the outer edge of the removed layer (the margin) is free of cancer cells.

Basal cell cancers tend to spread downward and outward below the skin's surface and to occur in cosmetically sensitive areas, such as the eyes, nose, lips, and ears. Mohs surgery is ideally suited to these situations and is usually the first choice for removing high-risk basal cell skin cancers (cancers that are most likely to return). The surgery is performed under local anesthesia and typically takes two to four hours, sometimes more. Much of that time is spent waiting while the removed tissue is analyzed, to see if the margin is cancer-free.

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