brown pigmented areas on the skin that can be a number of things:
benign (aging spots, scars, old or chronic collection of blood under the skin from venous stasis or after traumatic, seborrheic keratosis, freckles, melasma, moles or nevi) or malignant (basal cell carcinoma, melanoma). They can be congenital (present at birth) or acquired/arise later in life.
Aging spots are due to the gathering of skin pigment cells into patches or blotches as a result of aging & sun exposure, most commonly on the back of the hands. Freckles have the same etiology & are found in younger people or redhaired individuals. They are best treated with 1 or 2 ruby or yag Q-switched laser treatments. These can be performed with local or topical anesthetic. If large areas of the face are involved the CO2 or erbium laser is a better bet as the extra benefit of overall facial rejuvenation is achieved.
Seborrheic keratosis has a stuck on the skin appearance with an uneven non-ulcerated surface. It is treated by CO2 laser or surgical excision or freezing.
Melasma is a light tan to dark brown pigmentation of the face (cheek, forehead) in a mask like configuration. It is commonly seen in pregnant women or those taking birth control pills. The pigment lies at a deeper level than the depth reached by pigment lasers. It is best treated with creams as pigment lasers can lighten the more superficial skin & make the lesion look darker.
Moles are effectively lightened with ruby or yag lasers but require 2 to 6 treatments. If they are elevated they will need levelling after pigment removal by shaving or CO2 laser. Alternatively they can be shaved level with the skin surface & the base frozen with liquid nitrogen to prevent regrowth. It is hard to impossible to remove a large protruding lesion by liquid nitrogen alone. Also, if the liquid nitrogen is held to the skin for too long (more than 10 to 15 seconds) all the pigment cells may be killed resulting in an unsightly white spot.
Characteristics indicative of malignancy are skin ulceration, chronic drainage, recent noticeable change in an old skin lesion, recurrent skin infections, variegated or mixed coloration, irregular borders or surface & large size (more than 5mm). These lesions require biopsy. Also, any tissue removed should be sent to a pathologist for examination because physicians are commonly surprised by what looks benign but ends up being malignant. Current recommendations are that all congenital moles should be removed & sent for examination by a pathologist because of the inherent risk of cancerous degenaration in congenital moles.
In short if over the counter creams do not yield a prompt response it is best to see a qualified physician to be on the safe side. Any suspicous lesions should be biopsied & sent to a pathologist for examination to avoid missing a skin cancer.