The pathology of the MOHS examines the margins and checks if the margins are clear, Generally you would end up having a smaller defect with MOHS than a standard excision with a margin. The big thing is that MOHS almost guarantees removal and has the smallest chance of recurrence.
The MOHs technique is a tissue sparing surgical route for removal of low grade skin cancers. It is the best technique to remove skin cancers of the face due to the tissue sparing effect of the procedure. The MOHs procedure is necessary in order to ensure all the margins area clear of the cancer cells. A biopsy would not be adequate to removal the complete basal cell. Additionally, the closure from the excision is often longer than the excision. This is necessary in order to get a smooth and cosmetically elegant appearance.
I find that patients are often surprised at how long we need to make incision lines relative to the defect size. This often has to do with the need to ensure that the resulting closure has a smooth contour. Fortunately these incision lines usually fade with time.
Mohs is a tissue sparing technique, so no more tissue is removed than necessary. However, the closure is often longer than may be expected to achieve the best cosmetic result for the patients. Typically, the sites heal beautifully with almost unnoticeable scars. Biopsies do not check for margins--the tissue is processed completely differently than with Mohs and it is not possible to adequately check margins with a biopsy specimen.