Staging Melanoma
Stage I Melanoma

Stage I melanomas are localized tumors. This means the primary tumor has not spread to nearby lymph nodes or distant sites. Stage I melanomas are considered to be low-risk for recurrence and metastasis.

Stage I melanomas are defined by two primary characteristics:

  • Tumor thickness (known as Breslow depth): how deeply the tumor has penetrated the skin. Thickness is measured in millimeters (mm).

    • 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: a condition in which the epidermis that covers a portion of the primary melanoma is not intact. Ulceration is determined by microscopic evaluation of the tissue by a pathologist, not by what can be seen with the naked eye.
  • Mitoses: A condition of the cells being in a state of active division. Mitoses are determined by microscopic evaluation by a pathologist, not what can be seen with the naked eye, similar to ulceration. It will be defined as "present or not present" and should include a number of mitoses per mm2.

The designation of Clark level measures the depth of invasion according to the number of layers of skin the tumor has penetrated. There are five anatomic layers of the skin:

Clark level is no longer considered by the new American Joint Committee on Cancer (AJCC) staging system for melanoma, as a secondary characteristic of Stage I tumors no more than 1.0 mm thick. This has been replaced with mitoses.

Subclasses of Stage I Melanoma

Stage IA (T1aN0M0)

  • T1a: the tumor is no more than 1.0 millimeter (mm) thick, with no ulceration and no mitoses
  • N0: the tumor has not spread to nearby lymph nodes
  • M0: the tumor has not spread to sites distant from the primary tumor
Stage IB (T1bN0M0 or T2aN0M0)
  • T1b: the tumor is no more than 1.0 mm thick, with ulceration or prescence of > 1 mitoses
  • T2a: the tumor is 1.01-2.0 mm thick, with no ulceration
  • N0: the tumor has not spread to nearby lymph nodes
  • M0: the tumor has not spread to sites distant from the primary tumor
See also Stage I Treatment.