Optimal management of common acquired melanocytic nevi (moles): current perspectives

Abstract

Although common acquired melanocytic nevi are largely benign, they are probably one of the most common indications for cosmetic surgery encountered by dermatologists. With recent advances, noninvasive tools can largely determine the potential for malignancy, although they cannot supplant histology. Although surgical shave excision with its myriad modifications has been in vogue for decades, the lack of an adequate histological sample, the largely blind nature of the procedure, and the possibility of recurrence are persisting issues. Pigment-specific lasers were initially used in the Q-switched mode, which was based on the thermal relaxation time of the melanocyte (size 7 μm; 1 μsec), which is not the primary target in melanocytic nevus. The cluster of nevus cells (100 μm) probably lends itself to treatment with a millisecond laser rather than a nanosecond laser. Thus, normal mode pigment-specific lasers and pulsed ablative lasers (CO2/erbium [Er]:yttrium aluminum garnet [YAG]) are more suited to treat acquired melanocytic nevi. The complexities of treating this disorder can be overcome by following a structured approach by using lasers that achieve the appropriate depth to treat the three subtypes of nevi: junctional, compound, and dermal. Thus, junctional nevi respond to Q-switched/normal mode pigment lasers, where for the compound and dermal nevi, pulsed ablative laser (CO2/Er:YAG) may be needed. If surgical excision is employed, a wide margin and proper depth must be ensured, which is skill dependent. A lifelong follow-up for recurrence and melanoma is warranted in predisposed individuals, although melanoma is decidedly uncommon in most acquired melanocytic nevi, even though histological markers may be seen on evaluation.

Keywords: lasers; melanoma; nevus; surgery.

Figure 1

Classification of melanocytic nevi. Notes: ^∫Site-specific classification (acral, nail, genital, and flexural nevi). ^#Nevus of Ota/Ito, Mongolian spots, blue nevi, plexiform pigmented spindle-cell nevi. ^§Small congenital melanocytic nevi (up to 1.5 cm in diameter), intermediate congenital melanocytic nevi (1.5–19.9 cm). ^¶Large congenital melanocytic nevi (>20 cm); the surface changes include smooth, cerebriform, rugose, verrucous, or lobular. *Types: epidermis (junctional), both epidermis and dermis (compound), or dermis only (dermal or intradermal). **Follicular congenital melanocytic nevi.

Figure 2

Macular junctional melanocytic nevi showing increased skin markings.

Figure 3

Raised pigmented papular lesion pathognomic of a compound melanocytic nevi.

Figure 4

The three stages of melanocytic nevi, with loss of pigment and eventual resolution of lesion which mirrors the “Abtropfung” theory.

Figure 5

Compound nevi with “hair” emanating from the lesions, such lesions tend to recur after removal.

Figure 6

Recurrent nevus seen 6 months after surgical excision.

Figure 7

Classification of lasers used in common acquired melanocytic nevi. Abbreviations: Er:YAG, erbium yttrium aluminum garnet; KTP, potassium titanyl phosphate; Nd:YAG, neodymium yttrium aluminum garnet; OD, optical penetration depth; PDL, pulsed dye laser; Qsw, Q-switched; alex, alexandrite.

Figure 8

A diagrammatic comparison of the effect of pigment-specific lasers and ablative lasers in common acquired melanocytic nevi. The lack of persistent nevus cells with ablative lasers leads to less chance of recurrent nevus, which is a distinct possibility with pigment-specific lasers. Note: *Er:YAG (200–300 msec, pulse duration)/ultrapulse CO₂ (<1 msec, pulse duration). Abbreviations: Er:YAG, erbium yttrium aluminum garnet.

Figure 9

An algorithm for management of common acquired melanocytic nevi with lasers. Note: *For most nevi, ablative lasers can remove the lesions without the use pigment-specific lasers. Abbreviations: alex, alexandrite; Er:YAG, erbium yttrium aluminum garnet; fd, frequency-doubled; Nd:YAG, neodymium yttrium aluminum garnet; Qsw, Q-switched; Sp, shortpulsed.