epidermal pigmented lesions. Furthermore, in the absence of reproducible spatial thermal injury confinement, the risk of scarring and pigmentary changes is significant in the hands of inexperienced operators.
The pigment-nonselective erbium and CO2 lasers can be used to remove epidermal pigment effectively because of the ability to target H2O in the epidermis. The nonspecific thermal damage leads to destruction of the lesion with denuding of the epidermis. Pigment is thus damaged as a secondary event. This destruction is followed by healing that may have some erythema and possible pigmentary and textural changes.
■ Q-Switched Lasers
The fundamental principle behind laser treatment of cutaneous pigment and tattoos is selective destruction of undesired pigment with minimal collateral damage. This destruction is achieved by the delivery of energy at the absorptive wavelength of the selected chro-mophore. The exposure time must also be limited so that the heat generated by the laser-tissue interaction is confined to the target.
The target chromophore of pigmented lesions is the melanosome and that of tattoos, is the insoluble, submicrometer intracellular pigments. Q-switched lasers produce pulses in the nanosecond range. These high peak power lasers deliver light with a pulse width shorter than the approximately 1-ms thermal relaxation time of the melanosomes or the tattoo ink particles. Various Q-switched lasers (532-nm frequency-doubled Q-switched Nd:YAG, 694-nm ruby, 755-nm alexandrite, 1064-nm Nd:YAG) are therefore used for the treatment of various epidermal, dermal, and mixed epidermal and dermal pigmented lesions and tattoos (Table 3.2).
To date, Q-switched lasers have been shown to treat both epidermal and dermal pigmented lesions effectively in a safe, reproducible fashion. Q-switched lasers used for the treatment of superficial pigmented lesions include the 532-nm frequency-doubled Q-switched Nd:YAG, the 694-nm ruby, and the 755-nm alexandrite lasers. Strong absorption of light at these wavelengths by melanin makes these lasers an excel lent treatment modality for superficial pig-mented lesions. The Q-switched 694-nm ruby, 755-nm alexandrite and 1064-nm Nd:YAG lasers are useful for treating deeper pigmented lesions such as nevus of Ota and tattoos. The Q-switched 1064 nm laser should be used when treating patients with darker skin, because it reduces the risk of epidermal injury and pigmentary alteration.
■ Pulsed-Dye Laser
The short wavelength (510 nm) and 300-ns pigment lesion dye laser (PLDL) is highly effective in the treatment of superficial, pigmented lesions and red tattoos, but is no longer commercially available.
■ Long-Pulsed Lasers
To target large, pigmented lesions, such as hair follicles or nevocellular nevi, lasers with longer (millisecond- as opposed to nanosecond-range) pulse durations are more suitable (Table 3.1). These include the long-pulsed 694-nm ruby, 755-nm alexandrite, 810-nm diode and 1064-nm Nd:YAG lasers. The millisecond pulse width more closely matches the thermal relaxation time of the hair follicles or the nested melano-cytes. Collateral thermal damage results in injury to the stem cells located in the outer root sheath or the melanocytes adjacent to the target area that may actually not contain melanin. However, it is unlikely that every nevus cell is destroyed. Cautious follow-up of nevi treated with laser light is necessary.
■ Intense Pulsed Light Sources
Intense pulsed light (IPL) systems are high-intensity light sources, which emit polychromatic light (Table 3.3). Unlike lasers, these flash-lamps work with noncoherent light over a broad wavelength spectrum of 515-1200 nm. Because of the wide spectrum of potential combinations of wavelengths, pulse durations, pulse intervals, and fluences, IPLs have proven to very efficiently treat photodamaged pigmented lesions like solar lentigines and generalized dyschromia.
There are many types of pigmented lesions. Each varies in the amount, depth, and density of melanin or tattoo ink distribution. The approach to the treatment of cutaneous pigmentation depends on the location of the pigment (epidermal, dermal, or mixed), the way it is packaged (intracellular, extracellular) and the nature of the pigment (melanin or tattoo particles). The benign pigmented lesions which do respond well to laser treatment include: len-tigines, ephelides (freckles), nevus of Ota, nevus of Ito, and "blue" nevus. Varying results are obtained in cafe-au-lait maculae, nevus spilus, and nevus of Becker. Treatment of congenital and acquired nevi is still controversial because of the risk of incomplete destruction of deeper-situated nevus cells. Hyperpigmen-tation, like melasma and postinflammatory hyperpigmentation, only shows a moderate response. Finally, laser treatment in itself can result in postinflammatory hyperpigmentation.
In general, epidermal pigment is easier to eradicate than dermal pigment because of its proximity to the skin's surface. Several lasers can effectively treat epidermal lesions. These include the Q-switched laser systems, pulsed visible light lasers and flashlamps, CW lasers, and
CO2 or erbium lasers. The goal is to remove unwanted epidermal pigmentation, and as long as the injury is above the dermal-epidermal junction, it will heal without scarring.
■ Lentigo Simplex, Solar Lentigo
Lentigines are benign macular epidermal lesions caused by ultraviolet light, They contain melanin within keratinocytes and melanocytes. The superficial nature of lentigines allows the use of several lasers, including frequency-doubled Q-switched Nd:YAG, Q-switched ruby, alexandrite, Nd:YAG, pulsed 510 nm, CW argon, CO2 or erbium, and other pulsed visible-light lasers. Labial melanocytic macules are similar lesions found on the mucosal surface and respond well to treatment with Q-switched lasers (Fig. 3.2).
Lentigines frequently clear with 1-3 treatments. The argon laser (488 nm, 514 nm), the 510-nm pigment laser, and the 532-nm green light lasers treat lentigines with superior efficacy, especially lightly pigmented lesions in which less chromophore is present. These shorter wavelength lasers are better absorbed by melanin but have less penetration. Use of a broadband sunscreen helps prevent new lentig-ines from occurring as well as the recurrence of treated lesions.
Correct diagnosis is a primary concern when treating lentigines. Lentigo maligna should not be treated with laser. Although initially one can obtain excellent cosmetic results,
recurrences are frequently seen. Lentigo maligna frequently has an amelanotic portion, which is not susceptible to laser treatment and will allow for recurrence. These cases emphasize the importance of careful clinical assessment before any laser surgery and the need to advise patients to return for evaluation if pigmentation does return.
■ Seborrheic Keratosis
Seborrheic keratoses are benign epidermal lesions that have melanin distribution similar to lentigines and a thickened, hyperkeratotic epidermis. Liquid nitrogen cryotherapy and other surgical methods like CO2 or erbium laser are useful in treating these lesions, but are not practical modalities to tolerate in patients who have large numbers of lesions. Using pulsed green or Q-switched lasers offer the possibility to quickly and efficiently destroy hundreds of flat pigment seborrheic keratoses.
Ephelides or freckles are responsive to Q-switched laser treatment. Patients who tend to freckle are likely to refreckle with any sun exposure. At a follow-up of 24 months after laser treatment, 40% of patients showed partial recurrence. However, all the patients maintained >50% improvement. The use of a broad band sunscreen is therefore indicated.
■ Cafe-au-Lait Macules
Cafe-au-lait macules are light to dark brown flat hypermelanotic lesions and may be a solitary benign finding or associated with certain geno-dermatoses (e. g., neurofibromatosis). Histolog-ically, hypermelanosis is present within the epidermis and giant melanosomes may be present in both basal melanocytes and keratinocytes. Although cafe-au-lait macules are thin, superficial lesions, they are notoriously difficult to treat, and multiple treatments are required for even the possibility of complete eradication. There is probably a cellular influence in the dermis that triggers the pigmentation in the more superficial cells. This underlying biology may also explain why pigment recurrences are often observed. Lesions may remain clear for up to a year with spontaneous or UV-induced recurrences in more than 50% of cases. Patient education is important so that the possibility of recurrence is understood. However, given the significant disfigurement associated with many of these larger facial lesions, laser treatment is an excellent treatment option. Q-switched lasers with wavelengths of 532 nm or the pulsed 510-nm (Alster 1995) laser can adequately treat the cafe-au-lait macules (Fig. 3.3). Erbium laser superficial abrasion of the epidermis of a "Q-switched laser-resistant" cafe-au-lait macule has also been reported to be a successful treatment modality.
When darker-pigmented macules or papules (junctional or compound melanocytic nevi) lie within the cafe-au-lait macule, the lesion is called nevus spilus. The lasers used for cafe-au-lait macules have also been used for nevus spilus (Carpo et 1999). The darker lesions tend to respond better than the lighter cafe-au-lait
macule. There can be complete removal of the junctional or compound nevus portion but no improvement in the cafe-au-lait portion. Cases of nevus spilus transformation into melanoma have been reported in the literature. These cases emphasize the need for careful clinical assessment before any laser surgery, and continued evaluation after laser treatment.
Dermal-Epidermal Pigmented Lesions ■ Becker's Nevus
Becker's nevus is an uncommon pigmented hamartoma that develops during adolescence and occurs primarily in young men. The nevus is characterized by hypertrichosis and hyper-pigmentation and is usually located unilaterally over the shoulder, upper arm, scapula, or trunk. These lesions often require the use of millisecond pigment-specific lasers for treatment of the hair, but the pigment lightening is variable. Test sites with a variety a pigment-specific Q-switched and millisecond lasers or flashlamps is recommended to determine which one (or combination) will be the best treatment option (Fig. 3.4). More recently, ablation of the epidermis and superficial dermis with an erbium laser
has been shown to result in occasional complete pigment clearance with a single treatment.
■ Postinflammatory Hyperpigmentation
Treatment of postinflammatory hyperpigmentation with laser is unpredictable and often unsatisfactory. Furthermore, patients with hyperpigmentation following trauma are likely to respond to laser irradiation with an exacerbation of their pigment. The use of test sites is therefore recommended before an entire area is treated.
■ Postsclerotherapy Hyperpigmentation
Cutaneous pigmentation commonly occurs following sclerotherapy of varicose veins. Pigmentation most likely reflects hemosiderin deposition, which is secondary to extravasation of red blood cells through the damaged endothelium (Goldman et al. 1987). Hemosiderin has an absorption spectrum that peaks at 410-415 nm followed by a gradually sloping curve throughout the remainder of the visible spectrum. Several Q-switched or pulsed lasers have therefore been reported to result in significant resolution of hemosiderin pigmentation (Goldman 1987; Sanchez et al. 1981).
Melasma is an acquired, usually symmetric light to dark brown facial hypermelanosis. It is associated with multiple etiologic factors (pregnancy, racial, and endocrine), and one of the primary causes of its exacerbation appears to be exposure to sunlight. Although the results after Q-switched laser treatment are usually initially encouraging, repigmentation frequently occurs.
Destruction of the abnormal melanocytes with erbium:YAG or CO2 laser resurfacing has been attempted. It effectively improves melasma, however, there is almost universal appearance of transient postinflammatory hyperpigmentation which necessitates prompt and persistent intervention. A combination of pulsed CO2 laser followed by Q-switched alexandrite laser (QSAL) treatment to selectively eliminate the dermal melanin with the alexandrite laser has also been examined. Combined pulsed CO2 laser and QSAL showed a better result than CO2 or QSAL alone, but was associated with more frequent adverse effects. Long-term follow-up and a larger number of cases are required to determine its efficacy and safety for refractory melasma.
■ Nevocellular Nevi
Although laser treatment of many pigmented lesions is accepted, treatment of nevocellular nevi is an evolving field with much controversy. It has yet to be determined if laser treatment increases the risk of malignant transformation by irritating melanocytes or decreases it by decreasing the melanocytic load. For this reason, laser treatment of nevi should be undertaken cautiously.
■ Congenital Melanocytic Nevi
The management of giant congenital melanocytic nevi (GCMN) remains difficult. It has been well proved that there is an increased risk of malignant changes among patients with these lesions, although the amount of increased risk for each individual patient is not clear. There is also a balance to be achieved between limiting the risk of malignant change and minimizing the disfiguring appearance of these lesions. Sometimes GCMN are too large to be removed by multiple surgical excisions or use of osmotic tissue expanders. Removal of superficial nevus cells is possible by dermabrasion, curettage, shave excision, or laser. High energy CO2 laser therapy is less traumatic and can produce acceptable cosmetic results. Erbium laser treatment can also be used because it causes less thermal damage and faster wound healing. These techniques, although improving the cosmetic appearance, do not remove all nevus cell nests. Therefore they do not completely eliminate the risk of malignant transformation.
Treatment of giant, congenital nevi with a long-pulsed ruby laser has been reported. These systems show promise with follow-up for at least 8 years after laser treatment. There has been no evidence of malignant change in the treated areas. However, the longer laser-emitted pulse widths can lead to thermal damage of surrounding collagen with resultant scar formation. This is especially true with darker, thicker lesions with a deep dermal component, which are often the ones whose removal is most desired. Combination therapy is therefore under investigation where Q-switched or resurfacing lasers may be used first to reduce the superficial component, followed by one of the millisecond pigment-specific lasers.
■ Congenital and Acquired Small Melanocytic Nevi
The Q-switched ruby, alexandrite, and Nd:YAG lasers have been studied for treatment of mela-nocytic nevi (Goldberg 1995). Although clearing rates as high as 80% have been reported, short-pulsed lasers are not recommended for nevi because of the high postlaser treatment recurrence rates. Melanocytic nevi often have nested melanocytes with significant amounts of melanin and therefore may act more as a larger body than as individual melanosomes. It has therefore been suggested that longer pulsed ruby, alexandrite, or diode lasers or Q-switched lasers in combination with longer-pulsed lasers may provide a more effective treatment with fewer recurrences. All laser systems have been partially beneficial. No lesions have had complete histologic removal of all nevomelanocytes (Duke et al. 1999).
The development of Q-switched lasers has revolutionized the treatment of dermal melanocyto-sis. The dendritic cells found deep in the dermis are particularly sensitive to short-pulsed laser light, frequently resulting in complete lesional clearing without unwanted textural changes.
Nevus of Ota is a form of dermal melanocytic hamartoma that appears as a bluish discoloration in the trigeminal region. Histologic examination shows long, dermal melanocytes widely scattered in the upper half of the dermis. Nevus of Ito is a persistent grayish-blue discoloration with the same histologic characteristics of nevus of Ota, but is generally present on the shoulder or upper arm, in the area innervated by the posterior supraclavicular and lateral brachial cutaneous nerves.
The dermal melanocytes found within these lesions contain melanin and are highly amenable to treatment with Q-switched ruby (Geronemus 1992; Goldberg 1992), alexandrite (Alster 1995), or Nd:YAG lasers. Four to eight treatment sessions are typically required to treat these lesions. Possible side effects like postinflammatory hyperpigmentation, hypo-pigmentation or scarring, and recurrences are infrequent. Although there have been no reports of successful treatment of nevus of Ito, treatment with Q-switched lasers should be efficacious.
Blue nevi are benign melanocytic lesions that arise spontaneously in children or young adults. The melanocytes are deep within the dermis and the blue-black color results from the Tyn-dall light scattering effect of the overlying tissues. Although extremely rare, malignant blue nevi have been reported. Because of their benign nature, blue nevi are usually removed for cosmetic reasons. The deep dermal melanocytes respond well to Q-switched laser treatment, as long as the lesion does not extend into the deep subcutaneous tissue.
■ Acquired Bilateral Nevus of Ota-Like Macules (ABNOMs)
Acquired bilateral nevus of Ota-like macules (ABNOM), also called nevus fuscoceruleus zygomaticus or nevus of Hori, is a common Asian condition that is characterized by bluish hyperpigmentation in the bilateral malar regions. Unlike nevus of Ota, ABNOM is an acquired condition that often develops after 20 years of age, involves both sides of the face, and has no mucosal involvement. Histologi-cally, active melanin-synthesizing dermal melanocytes are dispersed in the papillary and middle portions of the dermis. Since these lesions are histologically a form of dermal melanocytosis like nevus of Ota, melanin-targeting lasers should be effective in the treatment. Although promising results in the treatment of Hori's nevus with Q-switched ruby, alexandrite, and Nd:YAG lasers have been reported, the treatment responses have been noted to be less effective than that of nevus of Ota. Multiple laser sessions are necessary to obtain cosmetically desired improvement. A higher rate of postinflammatory hyperpigmen-tation is often present after laser treatments.
The popularity of tattoos is burgeoning with 20-30 million tattooed individuals in the Western world. Requests for removal can be expected to rise concurrently with increased applications. Despite their relatively easy acquisition, the removal of tattoos has long been a real problem. Laser removal of tattoos is potentially a more cosmetically acceptable method of removing tattoos than surgical excision or der-mabrasion.
■ Tattoo Pigments
Tattoos, a form of exogenous pigment, are usually composed of multiple colors and various dyes. In contrast to drugs and cosmetics, tattoo pigments have never been controlled or regulated in any way, and the exact composition of a given tattoo pigment is often kept a "trade secret" by the manufacturer. In most cases, neither the tattoo artist nor the tattooed patient has any idea of the composition of the tattoo pigment.
Until recently, most coloring agents in tattoo pigment were inorganic heavy metal salts and oxides, like aluminum, titanium, cadmium, chromium, cobalt, copper, iron, lead, and mercury. There has been a shift in recent years away from these agents toward organic pigments, especially azo- and polycyclic compounds. These pigments are considered safer and well tolerated by the skin, although allergic reactions and phototoxicity occur.
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