Mohs micrographic surgery treats common forms of skin cancer by removing cancerous tissue layer by layer while preserving the maximum amount of healthy surrounding skin. Unlike traditional surgical excisions, Mohs surgery is unique because the entire process is performed and analyzed in sequential stages during a single visit. This staged, microscopic control means the total time commitment is highly unpredictable and can range significantly, often taking several hours. The exact duration depends entirely on the extent of the cancer beneath the surface of the skin, which is not fully known until the procedure is underway.
The Core Mohs Timeline: Stages and Cycles
The Mohs procedure is structured around cycles, with each cycle representing one stage of cancer removal and microscopic analysis. A single cycle begins with the Mohs surgeon administering local anesthesia, followed by the initial removal of the first thin layer of tissue. This initial surgical step typically requires only 5 to 15 minutes to complete.
Once the tissue is excised, the surgeon maps its orientation before it is taken to an on-site laboratory for processing. This is the primary waiting period, as technicians freeze, cut, stain, and mount the tissue onto slides for microscopic examination. This preparation and analysis usually takes between 40 and 60 minutes per stage.
During this time, the patient remains in a dedicated waiting area. If the microscopic examination reveals cancer cells still present, the surgeon precisely identifies the location and performs a new, targeted excision. This process repeats until a clear margin, meaning no remaining cancer cells, is confirmed under the microscope.
Factors Determining the Total Duration
The number of stages required to achieve a cancer-free margin is the primary variable determining the total length of the appointment. Each additional stage necessitates another cycle of excision and laboratory analysis, adding approximately one hour to the overall time. Since the extent of the subclinical cancer is unknown before the procedure, the final number of stages cannot be predicted.
Tumors that are larger, deeper, or located on anatomically complex areas like the nose, ears, or eyelids often require more stages due to intricate growth patterns. Aggressive cell types or tumors that have recurred after previous treatments also tend to spread more widely and deeply, increasing the likelihood of multiple excisions. The efficiency of the on-site Mohs laboratory and staff can also slightly influence the 40-to-60-minute waiting time between stages.
Patients should plan to be at the clinic for an average total time ranging from three to eight hours. This extended duration reflects the time taken for the highly precise, sequential lab work necessary to ensure the complete removal of the malignancy while conserving healthy tissue.
What Happens After Tumor Removal
Once the final microscopic stage confirms the tumor has been entirely removed, the wound repair phase begins. Its duration varies based on the size and location of the resulting surgical defect. Simple wounds may be closed with straightforward stitching, a process that might take only 30 minutes.
Larger or cosmetically sensitive defects often require complex reconstruction. This can involve techniques like a local flap, where nearby skin is moved, or a skin graft, where skin is taken from a distant site. These intricate closures demand greater surgical time, sometimes adding two hours or more to the overall procedure length. The surgeon determines the optimal method to achieve the best functional and aesthetic outcome.
Following the repair, the medical team provides detailed post-operative care instructions, including guidance on wound dressing and activity restrictions. A final check of the wound and discussion about follow-up appointments concludes the patient’s day before discharge.