Mohs Surgery: What It Is and Why Dermatologists Recommend It

Step 1: The visible cancer is removed along with a thin layer of surrounding tissue. Step 2: While you wait (usually 30-60 minutes), the tissue is processed, sliced, stained, and examined under a microscope by the Mohs surgeon. Step 3: If cancer cells are found at any margin, another thin layer is removed from exactly that area. Steps 2-3 are repeated until all margins are clear.

The entire process typically takes 2-4 hours, with most of that time spent waiting between stages. The actual cutting takes minutes per stage.

Mohs is recommended for: skin cancers on the face (nose, eyelids, ears, lips), areas where tissue preservation is critical (fingers, genitals), skin cancers with aggressive histology, recurrent skin cancers (previously treated and returned), large or poorly defined cancers, cancers in immunosuppressed patients.

For skin cancers on the trunk or limbs that are small and well-defined, standard excision is usually sufficient and Mohs is not necessary.

Arrive prepared to spend most of the day (bring a book, phone charger, snacks). You will be awake throughout — only local anesthesia is used. You can eat and drink normally. Bring a driver if the cancer is near your eye or if you feel anxious.

Between stages, you wait in the office with a temporary bandage. Most cancers are cleared in 1-3 stages. After the last stage, the wound is repaired — with stitches, a skin flap, or a skin graft depending on size and location.

Days 1-3: moderate swelling and bruising, especially on the face. Keep the wound clean and follow your surgeon's specific instructions. Pain is typically manageable with over-the-counter pain relievers. Days 4-14: stitches removed (timing depends on location). Swelling subsides. Avoid strenuous activity, heavy lifting, and bending over.

Weeks to months: the scar matures and fades. Scars on the face typically heal very well due to excellent blood supply. Ask about scar management (silicone strips, sunscreen on the scar) at your follow-up visit.

Standard excision removes the visible cancer plus a predetermined margin (4-6mm for BCC, wider for SCC and melanoma). The tissue is sent to a lab, and results come days later. If margins are positive, a second surgery is needed.

Mohs examines 100% of the margin in real-time, so you know the cancer is completely removed before leaving the office. It also preserves more healthy tissue — critical for cosmetically sensitive areas. The trade-off: Mohs takes longer, costs more, and requires a Mohs-trained surgeon.