Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) mycosis fungoides ?
    ### Response:
    Mycosis fungoides is the most common form of a type of blood cancer called cutaneous T-cell lymphoma. Cutaneous T-cell lymphomas occur when certain white blood cells, called T cells, become cancerous; these cancers characteristically affect the skin, causing different types of skin lesions.
    