Most patients underestimate likely scar size before Moh's surgery

(Reuters Health) - Patients who need to have a cancerous lesion removed from their face in a procedure known as Moh’s micrographic surgery are often taken aback by the size of the resulting scar, a new study finds.

While doctors can usually estimate how large an incision they’ll need to make, more than 80% of patients asked before their surgery underestimated the length of their resulting scar by about half, according to the report published in JAMA Network Open.

“Skin cancer is very common and it tends to happen in cosmetically sensitive and functionally important areas, such as the lips and eyelids,” said study coauthor Dr. Joseph Sobanko, director of dermatologic surgery education at the University of Pennsylvania, in Philadelphia. “These are areas where you not only want to restore appearance but also function.”

While patients may understand those goals, their expectation of how big of an incision would be needed was off by more than a factor of two, Sobanko and his colleagues found.

Patients see the diameter of the lesion and assume the incision won’t be much bigger than that. But because the lesions are generally circular, surgeons need to extend the incision so the skin will lie flat when the edges are closed. Sobanko compares the extensions, which are triangular in shape, to the dart or pleat in an article of clothing.

To give a better idea of how this works, Sobanko suggested cutting a circle out of a piece of construction paper. “Try pinching together the edges and you’ll see that they pucker up,” he said. “If you cut two triangles one on either end and then try to put the edges together it will work better.”

After seeing many unhappy patients, Sobanko and his colleagues decided to get a better sense of what patients expected prior to surgery. The researchers recruited 101 patients, 57 of whom were men, to help.

The patients were asked, while looking in a mirror, to draw on their faces with a washable marker what they thought would be the extent of the scar resulting from the surgery. Before the marker was washed off, the researchers took a photo of the expected scar dimensions.

The patients’ surgeons were also asked to draw on the patient’s skin the expected size and shape of the scar after surgery. Once again, the results were photographed.

After surgery, the researchers compared the two sets of estimates and measured the actual surgical scars. As it turned out, for 84 patients (83.2%), the scars were about twice as long as they had estimated, while 67 (77.9%) surgeons had correctly predicted the scar length.

The Penn team is now testing to see if having previous patients serve as mentors could help make expectations more realistic.

The new study shows why it’s important to help patients develop realistic expectations before the surgery, said Dr. Hooman Khorasani, chief of dermatologic and cosmetic surgery at the Icahn School of Medicine at Mount Sinai in New York City.

If you do the math, Khorasani said, the length of the scar will be about six times the diameter of the original lesion.

“This has to do with the fact that most tumors have roots under the skin and thus, on average, the amount of skin that needs to be removed is twice the size of the tumor that is visible to the naked eye,” he explained. “Most of these defects are closed in a linear fashion. In order to do that, it is simply a geometrical rule that one has to convert a circle into an ellipse and the ratio between the diameter of the circle to the length of the ellipse is three to one.”

“When they come in, we tell them it’s going to be much longer than they expect, but there are many things that can be done to make the scar disappear afterwards,” Khorasani said. “Six months after some dermabrasion and laser treatment most can’t even see the scar.”

SOURCE: JAMA Network Open, online March 11, 2020.