Gapless, edge-controlled skin cancer surgery (Mohs surgery)
Complete Circumferential Peripheral and Deep-Margin Assessment (CCPDMA)
Introduction
Skin cancer is the most commonly occurring cancer in humans and is a rapidly increasing problem. In the last three decades (1990 – 2020), the incidence has approximately tripled, but the possibilities for treatment have also improved.
If skin cancer is detected early and completely removed through surgery, a cure is possible in the vast majority of cases. The aim is to remove the tumor completely while removing as little surrounding healthy tissue as possible in order to achieve a visually and functionally good result (especially in aesthetically important areas such as the face). In particular, the so-called “white” or “non-melanoma” skin cancer (basal cell carcinoma, squamous cell carcinoma) develops primarily on skin exposed to the sun and therefore frequently on the face, scalp and ears.
A good procedure for minimally invasive yet still complete removal of skin cancer is “Mohs surgery”. It is named after its developer, the American physician Frederic Mohs (1910 – 2002), and is used in the USA and in much of Europe as a standard method of skin cancer surgery.
Why Mohs surgery and how does it work?
With “traditional” skin cancer surgery, there is always the possibility that the finest tumor extensions, which are not externally visible, are not completely removed and the tumor regrows in the same place within a few months or a few years. In most such cases, a further, much larger operation is then necessary.
Mohs surgery minimizes the risk of any small parts of the tumor remaining by examining the entire edge of the removed tissue under a microscope on all sides and over the entire depth without gaps. This examination takes an average of 30-60 minutes and is performed between excision (the removal of the tumor) and closure of the wound. Using a microscope in the laboratory right next to the operating room, the surgeon is able to detect any small remnants of skin cancer. These points can be traced back very precisely on the patient, and a little more skin tissue is removed in a targeted manner. This can be done in several steps, as often as necessary, always one hour apart, until no tumor remnants are visible under the microscope along the entire border of the excised tissue. Since the vast majority of Mohs procedures can be performed under local anesthesia, the patient can take a break from operating room during microscopy before the wound is finally closed.
The videos (for which we are grateful to Mika Blackmore-Esslinger) illustrate how the surgically removed tumors, along with the small safety margin of healthy skin, are cut into wafer-thin slices, stained, and examined under the microscope. The first example shows a tumor completely removed at first attempt. In the second example, the lateral incision edge, and in the third example the deep incision edge, both show residual tumor. Consequently, precise additional cutting must be performed at these sites.
Depending on the size of the skin damage, the wound is closed with direct suture, with a local flap (where healthy skin from the immediate vicinity is “moved” onto the wound and sewn in) or with a skin graft (where healthy skin is taken from another part of the body and transplanted onto the wound, where it heals).