Mohs surgery is most useful in treating skin cancers that demonstrate contiguous growth patterns that have a high risk of recurrence or are located in cosmetically sensitive areas such as the face, nose, ears, and eyelids. High-risk tumors include tumors that are larger than one inch in diameter, have indistinct borders, or have recurred after other treatments. 

The two most common types of skin cancers treated with Mohs surgery are basal cell carcinomas and squamous cell carcinomas. Both of these tumors grow in a contiguous fashion and can often grow beyond what is seen on the skin’s surface and can extend along structures such as nerves, blood vessels, and scars.  With the Mohs procedure, theses extensions can be followed and removed.  

Malignant melanoma that is invasive is not commonly treated with Mohs surgery unless the cancer is located in a cosmetically critical area.  Mohs surgery, however, is very useful in treating malignant melanoma that is not yet invasive (in situ), and can help prevent recurrences by facilitating the removal of the subclinical spread of the cancer.