Size of Mohs Wound. Could The Doctor Have Left A Smaller Scar?

The first and most important priority of Mohs surgery is to cure the cancer.  The second priority is to conserve tissue, but cure of cancer remains the top priority.  Typically the Mohs surgeon will remove a small amount of normal skin around the visible area of tumor and/or scar.  There is always going to be some variability in how much "normal" skin is removed along with the skin cancer.  This varies depending on the surgeon, the type of tumor (more aggressive tumors such as squamous cell cancer might justify more skin removal), the age of the patient, the exact location on the face (for example, the eyelid is a location where skin sparing is critical), whether or not the tumor is recurrent, etc.    

Usually the size of the first level is determined by the initial biopsy done. I have literally done tens of thousands of Mohs procedures over my career. When I do a biopsy and the read comes back from the lab, I can often tell how much wider and deeper I need to go with the first cut. And often I can get the full piece with one cut, and not need to go larger and wider and deeper with more and more levels. There's not a rule of thumb so to speak, but it depends on the site, the initial biopsy report, and the experience of the doctor performing the procedure. The purpose of Mohs is to preserve as much skin as possible and remove the tiniest amount possible for the smallest scar.