Clark's level

Clark's Level of Invasion is a system used to describe the depth of penetration of melanoma (a type of skin cancer) into the skin. It is one of the factors used to determine the stage of melanoma, which is crucial for prognosis and treatment planning. The system was named after Wallace Clark, who introduced it in the 1960s.

Overview

Melanoma is a malignant tumor of melanocytes, which are the cells responsible for producing melanin, the pigment that gives color to the skin. The depth of the tumor's invasion into the skin layers significantly affects the patient's prognosis. Clark's Level of Invasion categorizes this depth into five levels, with each level indicating a progressively deeper invasion and, generally, a worse prognosis.

Clark's Levels

The five levels of Clark's Level of Invasion are:

• Level I: Melanoma is confined to the epidermis, the outermost layer of skin. This stage is also known as in situ melanoma.
• Level II: The melanoma has invaded the papillary dermis, the upper layer of the dermis directly beneath the epidermis.
• Level III: The melanoma has filled the papillary dermis but has not yet invaded the reticular dermis, the deeper layer of the dermis.
• Level IV: The melanoma has invaded the reticular dermis.
• Level V: The melanoma has invaded the subcutaneous tissue, the layer of fat and connective tissue beneath the dermis.

Clinical Significance

The depth of invasion is a critical factor in determining the prognosis of melanoma. Generally, the higher the Clark's level, the greater the risk of the melanoma spreading (metastasizing) to other parts of the body, and the worse the prognosis. Clark's level is used in conjunction with the Breslow thickness, another measure of tumor depth, to accurately stage melanoma and guide treatment decisions.

Treatment and Prognosis

Treatment options for melanoma may include surgical removal of the tumor, immunotherapy, radiation therapy, and chemotherapy, depending on the stage of the disease. Early detection and treatment of melanoma, when it is still at a lower Clark's level, can significantly improve the prognosis.

Limitations

While Clark's Level of Invasion provides valuable information about the depth of melanoma invasion, it has some limitations. The introduction of the Breslow thickness, which measures the exact depth of the tumor in millimeters, has been found to be a more accurate predictor of prognosis. As a result, the Breslow thickness is more commonly used in clinical practice today. However, Clark's level can still provide useful information, especially in cases where the Breslow thickness is not available.

See Also

• Melanoma
• Skin cancer
• Breslow thickness
• Cancer staging