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Stage I Melanoma

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Stage I melanoma is defined as a melanoma that is up to 2 mm thick. A Stage I melanoma may or may not have ulceration. There is no evidence the cancer has spread to lymph nodes or distant sites (metastasis). There are two subclasses of Stage I melanoma: 1A, 1B.

Stage I Melanomas Are Defined by 3 Primary Characteristics

  • Tumor thickness (Breslow Depth): how deeply the tumor has penetrated the skin. Thickness is measured in millimeters (mm). For example:

    • 1 mm = .04 inch, or less than 1/16 inch (about equal to the edge of a penny)

    • 2 mm = between 1/16 and 1/8 inch (about equal to the edge of a nickel)

    • 4 mm = between 1/8 and 1/4 inch (about equal to the edges of two nickels)

  • Ulceration: when the epidermis (or top layer of skin)  that covers a portion of the primary melanoma is not intact. Ulceration can only be seen under a microscope, not by the naked eye.

  • Mitotic Count (Rate): is a secondary characteristic that describes how quickly the tumor cells are dividing. Mitotic count is calculated by a pathologist who counts the average number of actively dividing cells in the biopsy sample.


Note: Clark Level has been replaced as a criteria by the AJCC in 2010. 

There Are 2 Subclasses of Stage I Melanoma















Risk: Patients with Stage I Melanoma are considered low risk for local recurrence or for regional and distant metastases. Keep in mind that the statistics shown for survival are averages; everyone's cancer and survival rate is based on many factors and determined on an individual basis.

For more information, see stage I follow-up.


Stage I Melanoma:
Localized Tumor

Subclasses 1A, 1B


Localized tumor


Hasn't spread to lymph nodes or distant sites


Risk: You're considered to be at low risk for recurrence and metastasis when you have Stage I melanoma.

The following factors determine the stage of melanoma:


  • Tumor thickness:

    • Breslow Scale

  • Whether the tumor is with or without ulceration

  • Mitotic Count (Rate)

  • Whether the metastasis is microscopic (tiny tumors not visible to naked eye) or macroscopic (tumors large enough to be visible or  that can be felt)

  • Site of distant metastasis: skin vs other areas

  • Level of LDH (serum lactate dehydrogenase)