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Medically reviewed by Dr. C.H. Weaver M.D. 12/2018

In Situ Melanoma

Patients with melanoma in situ are treated by surgical removal of the lesion with the goal of obtaining minimal surgical margins that are free of any evidence of melanoma cells when examined under the microscope. Virtually all patients with melanoma in situ are cured following an adequate excision. The surgical guidelines for adequate excision are to remove the entire lesion (melanoma in situ) with a 0.5 cm margin of normal skin surrounding the lesion. This is confirmed by a pathologist who examines the removed specimen under the microscope. Inadequate excision of a melanoma in situ can lead to a recurrence of the lesion or progression in the area to a more advanced melanoma.(1)

For example, in one clinical study involving 121 patients with stage 0 melanoma, there were only 6 local recurrences (5%). Moreover, all local recurrences were treated successfully with more extensive surgery.(1)

Stage I Melanoma

Patients with stage I melanoma have cancer that is found in the outer layer of the skin (epidermis) and/or the upper part of the inner layer of skin (dermis), but has not spread to lymph nodes, and the primary melanoma is less than 2 millimeters (1/16 of an inch) thick.

The most important initial feature that is obtained from biopsy at the time that the melanoma is diagnosed is the thickness of the melanoma (Breslow thickness, measured in millimeters). A pathologist determines this thickness by examining the melanoma under a microscope and measuring the lesion from the top to the bottom. Based on the thickness of the tumor, melanoma is divided into 3 general categories:

  • Thin melanomas, which are less than or equal to 1 mm in thickness
  • Intermediate thickness melanomas, which are between 1 mm to 4 mm
  • Thick melanomas, which are greater than 4 mm

The thicker a melanoma is determined to be at the time of diagnosis, the greater the chance that it has spread. In general, melanoma spreads to the lymph nodes in the region of the primary cancer first.

In addition to thickness, there are other features that can determine the “aggressiveness” or likelihood that the tumor has spread.(1,2)

  • Microscopic absence of the continuous epidermis in the tissue overlying the melanoma, which is referred to as ulceration.
  • Penetration to Clark Level IV (invades deeper through the dermis, but still contained completely within the skin).
  • Regression.
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Surgical Treatment of Stage I Melanoma

The standard treatment of stage I melanoma is surgical removal with pathologically confirmed negative margins. Efforts been made to reduce the amount of normal skin removed without compromising the cure rate achieved with surgery. A melanoma greater than 1 millimeter appears to require a greater surgical margin to reduce the rate of recurrence at the site of origin. Most surgeons recommend a surgical margin of 2 centimeters (almost an inch) surrounding the entire cancer for melanomas greater than 1 mm. The need for skin grafting occurs in approximately 10% of patients. Surgical margins greater than 2 cm are no more effective and require skin grafting in a higher fraction of patients (up to 50%).

Evaluation of the regional lymph nodes by performing a sentinel lymph node biopsy (SLNB) as a staging procedure for patients with a primary melanoma greater than 1 mm is recommended. SLNB should also be considered in patients with thin melanomas (< 1 mm) and adverse prognostic factors, such as vertical growth phase, Clark Level IV, regression, and ulceration.(3,4)

The surgical treatment of stage I melanoma typically involves a single procedure in which a local excision of the cancer is performed as well as a SLNB. Approximately 15% of patients undergoing SLNB have a positive SLN (pathologically stage III). Ninety-five percent of patients with a confirmed negative “sentinel node” are free of cancer and require no additional treatment.(5)

Over 90% of patients with melanomas of less than 1 mm are cured following surgical removal of the melanoma. In one clinical study of patients treated at the Mayo Clinic, the 5-year survival rate for stage 1 melanoma of 0.75 mm or less was 98%.

Questions to Ask your Physician

Patients with melanoma of less than 1 millimeter should ask their physicians whether or not their melanoma demonstrated any evidence of ulceration, vertical growth phase, regression, or whether it is Clark level IV. Patients should also inquire about the treatment results achieved at the cancer center or institution where they are considering treatment.

Strategies to Improve Treatment

Cure rates are so high with melanoma in situ that there are essentially no outstanding treatment issues. However, there are outstanding issues for the prevention of the development of additional melanomas. The diagnosis of melanoma in situ, which is believed to be a precursor for invasive melanoma, may be an indication that genetic and environmental influences may be present in an individual that place them at increased risk for developing other in situ or melanomas in the future. Individuals with melanoma in situ should have routine skin evaluations performed by dermatologists bi-annually.

Avoiding the major cause of cutaneous melanoma, sun exposure, is of crucial importance in preventing new melanomas. The guidelines from the American Academy of Dermatology include:

  • Use a broad-spectrum sunscreen with a SPF of at least 15 on all exposed skin, including the lips, even on cloudy days.
  • If exposed to water, either through swimming or sweating, a water-resistant sunscreen should be used.
  • Reapply sunscreen frequently.
  • Wear a broad-brimmed hat and sunglasses.
  • Sit in the shade whenever possible.
  • Wear protective, tightly-woven clothing.
  • Plan outdoor activities early or late in the day to avoid peak sunlight hours between 10 am and 4 pm.


  1. Wagner JD, Gordon MS, Chuang TY, et al.: Current therapy of cutaneous melanoma. Plast Reconstr Surg 105 (5): 1774-99; quiz 1800-1, 2000.
  2. Cohn-Cedermark G, Rutqvist LE, Andersson R, et al.: Long term results of a randomized study by the Swedish Melanoma Study Group on 2-cm versus 5-cm resection margins for patients with cutaneous melanoma with a tumor thickness of 0.8-2.0 mm. Cancer 89 (7): 1495-501, 2000.
  3. Balch CM, Soong SJ, Smith T, et al.: Long-term results of a prospective surgical trial comparing 2 cm vs. 4 cm excision margins for 740 patients with 1-4 mm melanomas. Ann Surg Oncol 8 (2): 101-8, 2001.
  4. Heaton KM, Sussman JJ, Gershenwald JE, et al.: Surgical margins and prognostic factors in patients with thick (>4mm) primary melanoma. Ann Surg Oncol 5 (4): 322-8, 1998.
  5. Wong SL, Balch CM, Hurley P, et al.: Sentinel lymph node biopsy for melanoma: American Society of Clinical Oncology and Society of Surgical Oncology joint clinical practice guideline. J Clin Oncol 30 (23): 2912-8, 2012.