ACTINIC KERATOSIS: PRECANCER 
An actinic keratosis (AK) is a rough, dry, scaly patch or growth that forms on the skin. An AK forms when the skin is badly damaged by ultraviolet (UV) rays from the sun or indoor tanning.
Treatment Options 
CURETTAGE AND DESICCATION
The physician scrapes or shaves off part or all of the lesion, then applies heat or a chemical agent to stop the bleeding and potentially kill any remaining AK cells.
CRYOSURGERY
The physician applies liquid nitrogen to the AK to freeze the tissue. Later, the lesion and surrounding frozen skin may blister or become crusted and fall off.
PHOTODYNAMIC THERAPY
(PDT) is especially useful for widespread lesions on the face and scalp. The physician applies a light-sensitizing topical agent to the lesions, then uses a strong light to activate the topical agent, destroying the AKs while sparing healthy tissue.
COMBINATION THERAPY
Doctors may combine therapies for a period of time to treat AKs. Typically, treatment regimens combine cryosurgery with PDT or a topical agent like imiquimod, diclofenac, ingenol mebutate, or 5-fluorouracil (5-FU). The topical medications and PDT may also be used alternately every three months, six months or year, as determined by the physician at follow-up skin examinations.

TOPICAL TREATMENTS
If you have numerous or widespread actinic keratoses, your doctor may prescribe a topical cream, gel or solution. These can treat visible and invisible lesions with a minimal risk of scarring. Doctors sometimes refer to this type of therapy as “field therapy,” since the topical treatments can cover a wide field of skin as opposed to targeting isolated lesions.
» 5-fluorouracil (Carac®, Efudex®, Fluoroplex®): a form of topical chemotherapy.
» Imiquimod (Aldara®, Zyclara®): A form of topical immunotherapy, it stimulates the immune system to produce interferon, a chemical that attacks cancerous and precancerous cells.
» Ingenol mebutate (Picato®): A rapidly effective topical therapy derived from plants. An immunologic mechanism of action has been proposed.