Mohs micrographic surgery is a precise, layered technique used primarily to remove common skin cancers like basal cell carcinoma and squamous cell carcinoma. This specialized outpatient procedure is known for its high cure rate and tissue-sparing approach, making it particularly valuable for cancers on cosmetically sensitive areas such as the face. While the actual surgery is quick, the entire process is performed in stages and can range from approximately three to eight hours. Patients should plan for the possibility of spending the entire day at the clinic, as the duration depends on the number of stages necessary to achieve a clear margin, meaning the entire tumor has been removed.
The Step-by-Step Timeline
The Mohs procedure is structured around an iterative cycle of removal and microscopic analysis. A single stage involves three distinct steps, with the waiting period being the longest for the patient. The surgical removal of a thin layer of tissue containing the visible tumor and a small surrounding margin is typically a very fast process, often taking only about 10 to 15 minutes after the local anesthetic has taken effect.
Once the tissue is excised, it is immediately mapped, color-coded, and sent to an on-site laboratory for processing. The laboratory work involves freezing the specimen, cutting thin horizontal sections, staining them, and placing them on slides for the surgeon to examine under a microscope. The tissue preparation and microscopic examination commonly take between 45 and 60 minutes. During this time, the patient waits comfortably in a designated area with a temporary bandage covering the surgical site.
If the microscopic analysis confirms that no cancer cells remain at the edges of the removed tissue, the margins are considered clear, and the removal phase is complete. If cancer cells are identified, the surgeon uses the color-coded map to pinpoint the exact location of the remaining cancer. The patient is then brought back to the operating room for a second stage, where only the area with residual cancer is removed. This staged process repeats until a clear margin is confirmed.
Variables That Extend the Procedure Time
The primary factor determining the total time is the number of stages required to completely remove the skin cancer. Each additional stage directly adds the time needed for excision and lab work, extending the patient’s time in the clinic. While many procedures are completed in one or two stages, patients may require three or more stages for more extensive tumors.
The size and depth of the cancerous growth significantly influence how many stages will be necessary. Larger tumors and those that have grown deeper into the tissue layers will inherently require more layers of tissue to be removed before a clear margin is achieved. Cancers located on areas with complex anatomy or limited surrounding tissue, such as the nose, eyelids, lips, or ears, often necessitate more meticulous and time-consuming excisions to preserve as much healthy tissue as possible.
The microscopic characteristics of the cancer also play a role in procedural length. Tumors with aggressive subtypes or those with ill-defined clinical borders typically require a wider or deeper removal, which increases the likelihood of needing multiple stages.
Wound Closure and Post-Procedure Time
Once the Mohs surgeon confirms the final layer is cancer-free, the remaining open surgical wound must be repaired. This final phase, the wound closure or reconstruction, is the last major time commitment of the day. The method of repair is determined by the size and location of the resulting surgical defect.
For smaller wounds, a simple linear closure with sutures may be performed, which typically adds about 30 to 60 minutes to the overall procedure time. Larger or more complex defects may require advanced reconstructive techniques, such as a skin flap or a skin graft. These more involved reconstructions can take an additional hour or two, depending on the complexity of the repair.
Following the wound closure, the final minutes of the appointment are dedicated to dressing the wound and reviewing post-operative instructions with the patient and their caretaker. This includes detailed guidance on wound care, activity restrictions, and when to schedule the follow-up appointment for suture removal.