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MOHS Surgery


Mohs surgery, or Mohs micrographic surgery, is a skin-conservative surgical technique used in the treatment of basal cell carcinoma, squamous cell carcinoma, and other high-risk tumors in surgically complex locations on the body (such as the face). Mohs surgery offers complete excision of cancerous tissue under microscopic margin control, ensuring the highest cure rate, and maximizes the preservation of surrounding healthy tissue.


Mohs surgery usually is a single-day procedure, performed under local anaesthesia, meaning that the patient remains completely conscious during the surgery. It involves the following steps:

  • The visible tumor and a small margin of healthy tissue is meticulously outlined using a skin marker. Then, a reference grid is drawn.
  • The marked area is skillfully excised.
  • The excised tissue is divided into two or more sections and marked using a special color coding technique to precisely differentiate the remaining cancerous tissue from the healthy tissue.
  • A mapping process takes place. It ensures that residual tumor seen under the microscope can later be matched to the exact location on the patient, using a paper map or digital photographs as well as image processing software.
  • The horizontal sections of the entire excision margin are created.
  • The surgeon examines the sections to find any cancerous cells that may remain.
  • The residual cancerous areas (if there are any) are precisely drawn on the map or a digital image to identify the area on the patient where more tissue needs to be removed.
  • If there is need, more tissue is removed, and the process is repeated, until there is no longer cancerous tissue present at the site.
  • After a successful surgery, the wound is closed.
mohs surgery


Undoubtedly, Mohs surgery is most precise. The excised sections are histologically tested on the day of the procedure, and combined with the mapping technique, allows the surgeon to close the wound only after all cancerous tissue has been removed. In a standard excision, the tissue sample is histologically tested over a few days, after the wound has already been closed. During the examination of the samples, a pathologist looks for any remains of skin cancer at the margin of each section, nonetheless, in contrast to Mohs surgery, these are only fractions of the actual excision margin. It means that histological testing in a standard excision does not examine the specimen as closely as it is examined in the Mohs procedure. If any tumour is still visible after having performed a standard excision, the patient is usually offered the Mohs procedure. Pennsylvania Dermatology Specialists will assess which type of surgery would be the most suitable option for you.