Breslow thickness

The depth of a melanoma in millimetres, measured under the microscope from the top of the granular layer of the epidermis to its deepest point. Introduced by Alexander Breslow in 1970, it is the strongest single predictor of outcome and sets the width of the wide local excision and whether a sentinel node biopsy is offered.

Related terms

• Condition

  Melanoma

  A cancer of the pigment-producing cells (melanocytes) of the skin. It is the most serious of the common skin cancers because it can spread to the lymph nodes and other organs; found early, it is usually cured by excision. New Zealand and Australia have the highest rates in the world.

• Procedure

  Wide local excision

  The second operation after a melanoma is diagnosed: removal of a measured margin of normal-looking skin and fat around the biopsy scar, down to the fascia, to clear any remaining cancer cells. The margin, 5 mm to 2 cm, is set by the Breslow thickness.

• Procedure

  Sentinel lymph node biopsy

  Removal of the first lymph node (or nodes) that drain the skin around a melanoma, located with a radioactive tracer and a blue dye, to check for microscopic spread. A staging test that guides follow-up and further treatment; offered for melanomas 1 mm thick or more, or 0.8 mm with high-risk features.

Articles mentioning this term

1. Patient information · 26 September 2026

   Melanoma surgery

   Wide local excision and sentinel node biopsy after melanoma: why the margin follows Breslow thickness, what happens on the day, the risks and follow-up.

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