The staging system for melanoma has recently been revised, but continues to be based on primary tumor thickness, ulceration of the primary tumor, lymph node involvement, and distant metastasis. Historically, the staging system for primary melanoma was based on the Clark’s level and Breslow thickness. A common mistake with a new diagnosis has been to confuse Clark’s level with stage. Unlike stage, the Clark’s level describes a primary melanoma tumor microscopically, dividing the skin into 5 levels and assigning the melanoma to a different level based on how deep the melanoma penetrated.
- Clark’s Level I: Melanomas confined to the outermost layer of the skin, the epidermis. Also called “melanoma in-situ.”
- Clark’s Level II: Penetration by melanomas into the second layer of the skin, the dermis.
- Clark’s Levels III-IV: Melanomas invade deeper through the dermis, but are still contained completely within the skin.
- Clark’s Level V: Penetration of melanoma into the fat of the skin beneath the dermis, penetration into the third layer of the skin, the subcutis.
Since the division of skin layers and skin thickness is variable, the Clark’s level is somewhat subjective according to the pathologist making the reading. Due to its subjectivity and variability, the Clark’s Level is a less significant prognostic factor in the new staging system. However, the Breslow thickness continues to be an important measurement since it is more exact, more reproducible, and less subjective. The Breslow thickness is measured in millimeters and defines the vertical thickness (how far tumor extends into the skin) of a primary melanoma.
The Tumor-Node-Metastasis (TNM) classification system may also be encountered in melanoma staging. The TNM classification is used by pathologists to stage melanoma by describing tumor thickness, nodal involvement and presence of metastasis.
Recent studies indicate that ulceration (microscopic absence of continuous epidermis in tissue overlying the melanoma) of the primary tumor, the number of lymph nodes involved, sites of distant metastases and elevation in levels of blood enzyme called lactate dehydrogenase (LDH) are the most valuable prognostic factors for melanoma. A revised staging system by the American Joint Committee on Cancer (AJCC) took effect nationwide in January 2003.
The following is a simplified staging system useful for determining treatment and estimating outcomes. This staging system implies that the status of local lymph nodes is known from examination under the microscope. If direct surgical examination is not done, some patients staged as clinical stage II will in fact have stage III disease with lymph node involvement. In order to learn more about the most recent information available concerning the treatment of melanoma cancer, click on the appropriate stage.
Melanoma in Situ: Malignant melanoma cells are found only in the outer layer of skin cells (epidermis) and have not invaded to deeper layers.
Stage I: Malignant melanoma 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. The melanoma is < 1 mm with or without ulceration or 1-2 mm without ulceration. Stage I melanoma is further divided into stage IA and IB.
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- Stage IA: The malignant melanoma is not more than 1 millimeter (less than 1/16 of an inch) thick, with no ulceration. The tumor is in the epidermis and upper layer of the dermis.
- Stage IB: The malignant melanoma is either not more than 1 millimeter thick, with ulceration, and may have spread into the dermis or the tissues below the skin; or 1 to 2 millimeters (more than 1/16 inch) thick, with no ulceration.
Stage II: The malignant melanoma is 1 to 2 millimeters with ulceration or > 2 mm with or without ulceration. Malignant melanoma has spread to the lower part of the inner layer of skin (dermis), but has not spread into the tissue below the dermis or into nearby lymph nodes. Stage II melanoma is further divided into stage IIA, IIB and IIC.
- Stage IIA: The malignant melanoma is either 1 to 2 millimeters thick, with ulceration; or 2 to 4 millimeters (a little more than 1/8 of an inch) thick, with no ulceration.
- Stage IIB: The malignant melanoma is either 2 to 4 millimeters thick, with ulceration; or more than 4 millimeters thick, with no ulceration.
- Stage IIC: The malignant melanoma is more than 4 millimeters thick, with ulceration.
Stage III: The malignant melanoma can be any thickness with spread to regional lymph nodes. Stage III melanoma is further divided into stage IIIA, IIIB and IIIC.
- Stage IIIA: The malignant melanoma may have spread to as many as 3 nearby lymph nodes, but can only be seen with a microscope.
- Stage IIIB: The malignant melanoma has either spread to as many as 3 lymph nodes and may not be visible without a microscope; or has satellite tumors (additional tumor growths within 1 inch of the original tumor) and has not spread to lymph nodes.
- Stage IIIC: The malignant melanoma has either spread to as many as 4 or more lymph nodes and can be seen without a microscope; or has lymph nodes that may not be moveable; or has satellite tumors and may have spread to lymph nodes.
Stage IV: The primary malignant melanoma is any size, but has spread to distant lymph nodes and/or distant sites.
Locally Recurrent Melanoma: Malignant melanoma has recurred, but is limited to skin and/or regional lymph nodes.
Recurrent and Refractory Stage IV Melanoma: Patients who have not responded to or progressed after initial systemic therapy (chemotherapy and/or biologic therapy) or have malignant melanoma that has recurred.