A wide local excision for melanoma typically cuts down through all the skin and subcutaneous fat to the level of the muscular fascia, the tough connective tissue layer that sits on top of the muscle. For most invasive melanomas, that means removing everything from the skin surface down to that fascial plane. The actual depth in centimeters varies by body location because subcutaneous fat thickness differs dramatically between, say, the back and the scalp.
What Gets Removed and How Deep
The depth of a wide local excision is defined by anatomical layers rather than a fixed number of millimeters. For invasive melanoma, the standard is to remove all skin and underlying subcutaneous tissue down to the muscular fascia. The fascia itself is generally left in place because removing it has not been shown to improve outcomes.
This means the surgery passes through three distinct layers: the full thickness of skin (epidermis and dermis), the entire fat layer beneath it, and stops at the firm white sheet of tissue covering the muscle. On the abdomen or thigh, where fat can be several centimeters thick, this creates a substantially deeper wound than on the forehead or shin, where the fat layer is thin and the fascia sits close to the surface.
Melanoma in situ, the earliest stage where abnormal cells haven’t grown beyond the top layer of skin, is the exception. Because there’s no risk of spread into deeper lymphatic channels, the excision only needs to include the skin and a small amount of superficial fat underneath, just enough to ensure the full dermis has been removed. This is a notably shallower procedure.
Peripheral Margins by Tumor Thickness
While depth follows those anatomical landmarks, the horizontal distance around the melanoma (the peripheral margin) is determined by how thick the tumor is, measured in millimeters on the pathology report using what’s called Breslow thickness.
- Melanoma in situ: 0.5 cm margin around the visible lesion
- 1 mm or less (thin melanoma): 1 cm margin
- 1 to 2 mm: 1 to 2 cm margin
- Greater than 2 mm: 2 cm margin
These numbers come from the current NCCN guidelines and are echoed by the European Society for Medical Oncology. They represent a balance between removing enough tissue to prevent recurrence and keeping the wound manageable. Decades of clinical trials have shown that going wider than 2 cm does not improve survival, but it does increase complications.
Why Depth Varies by Body Site
Because the target is a specific tissue layer rather than a set measurement, two people with identical melanomas can end up with very different wound depths depending on where on the body the melanoma sits. On the back of someone with average body composition, subcutaneous fat might be 2 to 3 cm thick, making the excision relatively deep. On the scalp, the fat layer can be just a few millimeters, so the fascia (in this case, the connective tissue over the skull) is reached quickly.
Areas like the face, hands, and feet present particular challenges. The fat layer is thin, important structures like nerves and tendons sit close to the surface, and removing tissue to the fascia can be more complex. Surgeons sometimes adapt their approach in these locations, using techniques like Mohs surgery that check margins microscopically during the procedure to spare as much healthy tissue as possible while still clearing the cancer.
How Wound Closure Works After Excision
The depth and width of the excision together determine how the wound gets closed. Small, shallow excisions, particularly for melanoma in situ, can often be stitched closed directly. As excisions get deeper and wider, the options shift toward local tissue flaps, where nearby skin is rearranged to fill the gap, or skin grafts taken from another part of the body.
Wider and deeper excisions carry a higher risk of complications: longer healing times, chronic pain at the site, and a greater chance of needing reconstructive surgery. Long-term follow-up data have linked wider margins with poorer quality-of-life outcomes, including prolonged rehabilitation and increased healthcare costs. This is one reason modern guidelines have settled on the narrowest margins that still provide adequate cancer clearance.
The Initial Biopsy vs. the Wide Local Excision
If you’re preparing for a wide local excision, you’ve likely already had a biopsy that diagnosed the melanoma and measured its thickness. That initial biopsy is intentionally kept small, with margins no wider than about 5 mm. The reason is practical: if a sentinel lymph node biopsy is needed (typically recommended for melanomas thicker than 0.8 mm), the lymphatic drainage pathways around the melanoma site need to be intact. Cutting too wide during the initial biopsy can disrupt those pathways and make the lymph node mapping less accurate.
The wide local excision then happens as a second, planned surgery. The surgeon uses the pathology results from the biopsy to determine how wide and deep to cut. If a sentinel lymph node biopsy is indicated, it’s usually performed at the same time as the wide local excision, before the wider cut is made.
What to Expect in Practice
For thin melanomas (1 mm or less), the surgery is relatively minor. You’re looking at a 1 cm margin around the scar from your biopsy, taken down through the fat to the fascia. Depending on location, this wound is often closed with stitches the same day, and recovery takes a few weeks. For thicker melanomas requiring 2 cm margins, the wound is larger and deeper, making skin grafts or flaps more likely, especially on the legs or other areas where skin is tight. Recovery can stretch to several weeks or longer if a graft is involved.
The tissue removed during surgery is examined by a pathologist, who measures the closest distance between the melanoma and the edges of the removed tissue, both around the sides and at the deep margin. A clear deep margin, meaning no melanoma cells are found near the bottom of the specimen at the fascial level, confirms that the excision went deep enough.