Laser for Pigmented Lesions
Pigmented lesions have been associated with beauty as well as disease. “Beauty marks” may be the signature of those who have a unique facial birthmark, but others may seek to remove unsightly moles or pigmented skin lesions. Sun exposure may also produce pigmentation changes that may be either cosmetically undesirable or are pathologically of concern.
As a physician who treats many skin problems, it is Dr. Rasmussen’s role to determine which pigmented skin lesions warrant biopsy with histologic evaluation as opposed to those lesions that are candidates for cosmetic removal – either by shaving, definitive excision, or laser treatment. With the advent of pigment-specific lasers, selective treatment of many pigmented skin lesions is possible, leaving the non pigmented portion relatively undisturbed and making an excellent outcome probable. Among pigmented lesions amenable to laser treatment are solar lentigenes (“sunspots”), cafe-au-lait spots, freckles, post inflammatory hyperpigmentation, melasma, and a variety of benign nevi (“moles”).
Some pigmented skin lesions should not be treated by laser. These include melanoma, lesions that could be confused with melanoma (such as dysplastic nevi), and lesions that have the potential to develop into melanoma (such as lentigo maligna and certain nevi). Biopsy should be performed prior to laser treatment of any uncertain pigmented skin lesion because ablative therapy carries the risk of disguising it.
The range of effects of laser on a pigmented lesion depends on the amount of pigment in the lesion, the depth the pigment is located within the skin, and skin type and condition. Laser factors that effect successful treatment include wavelength, energy and exposure time. The goal is to select the laser which delivers sufficient amount of energy of the proper wavelength and pulse durations to destroy a target with limited damage to surrounding normal tissue. Commonly used lasers include the pulsed dye pigment laser, tunable pulsed dye laser, Q-switched ruby, Nd:YAG, and Q-switched alexandrite laser. Like the vascular laser, multiple treatments are frequently necessary for best results.
Of note, the same principles noted above for pigmented skin lesions apply to the removal of pigmented tattoos. However, there are several other factors which effect results. These are based on whether the tattoo was placed professionally, since this affects depth of pigment (professional tattoos are usually deeper in the skin and more refractory to treatment), type of pigment used (professional tattoos usually contain many different dyes, occasionally mixed with metallic elements, and pigments with iron or titanium oxides can undergo immediate pigment darkening), color (professional tattoos often have a variety of colors, and the best wavelength must be selected to treat the individual tattoo pigment), and complexity (professional tattoos may result in textural changes of the skin, even scarring, that may not be evident on casual inspection). Therefore, while amateur tattoos can usually be removed completely in a few treatments with superior cosmetic results, laser treatment of professional tattoos may result in hyperpigmentation, hypopigmentation, areas of faint ink persistence, and mild textural skin changes. The goal of laser treatment of the complex multicolored tattoo is to provide the patient with a result that is unrecognizable as a tattoo on casual inspection.