Definition:

Clark level IV skin cancerlisten (klark LEH-vul … skin KAN-ser)

Skin cancer that has spread down into the reticular dermis (the thick bottom layer of the dermis).

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Clark levels of skin cancer; drawing shows skin with five thin lesions of different depths. In the first lesion (Clark Level I), the cancer is in the epidermis only. In the second lesion (Clark Level II), the cancer has begun to spread into the papillary dermis (upper layer of the dermis). In the third lesion (Clark Level III), the cancer has spread through the papillary dermis into the papillary-reticular dermal interface but not into the reticular dermis (lower layer of the dermis). In the fourth lesion (Clark Level IV), the cancer has spread into the reticular dermis. In the fifth lesion (Clark Level V), the cancer has spread into the subcutaneous tissue.