Cutaneous T-cell lymphoma (CTCL), also known as mycosis fungoides, is a rare type of lymphocytic cancer in which certain cells of the lymphatic system, called T-lymphocytes or T-cells, become cancerous (malignant) and affect the skin.

The lymphatic system is part of the immune system. It is made up of tiny tubes that branch, like blood vessels, into all parts of the body, including the skin.

These vessels, called lymph vessels, carry lymph (a milky body fluid that contains lymphocytes, proteins...