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 activily 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.