Evolution of Spitz nevi
The natural evolution of melanocytic nevi is a complex, multifactorial process involving constitutional and environmental factors. Among the various types of melanocytic nevi, Spitz nevi are the most controversial due to their morphologic vicinity to melanoma. Spitz nevi usually present as solitary, pink-to-red plaques or nodules, but pigmented Spitz nevi are also commonly seen. Spitz nevi usually appear in children and young adults, they peak during the second and third decades of life, and are only rarely seen from the seventh decade to the ninth decade. Indpendently of age, sex, location, palpability, and pigmentation of the lesion, most Spitz nevi tend to go through spontaneous involution over time. A majority of Spitz nevi exhibit an involution pattern over a period of 2 years. Spontaneous involution seems a plausible explanation for the epidemiologic data reporting the frequency of Spitz nevi as being inversely correlated to pa- tient age. The 2 main variants of Spitz nevi are the amelanotic and the pigmented ones.
Classic Spitz nevi are usually nonpigmented plaques or nodules commonly found on the face and limbs of children and young adults. However, the spreading use of dermoscopy has allowed the recognition of an increasing number of pigmented Spitz nevi because of the unique morphologic features revealed by the dermatoscope.
Globular pattern
Most commonly the initial dermoscopic face of pigmented Spitz nevi is represented by a globular lesion which tends to acquire the classic starburst appearance after a variable number of months.
Starburst pattern
The starburst pattern is typified by streaks, pseudopods, or finger-like projections regularly distributed on the periphery of an otherwise symmetric and hyperpigmented macule or plaque. The presence of streaks is not pathognomonic in Spitz nevi because they can also be found in melanoma, representing the behavior of a benign or malignant lesion by growing horizontally. In benign lesions like Spitz nevi, streaks tend to disappear over time as soon as the lesions stop growing. In this stable phase Spitz nevi are thus seen in dermoscopy as homogeneous, heavily pigmented lesions which can be more difficult to recognize.
Homogenous pattern
Their homogenous pattern is typified by structureless brown- to-black pigmentation. Over a variable period of several months to a few years, a progressive decrease in pigment occurs until possible complete involution of the lesion is observed.
Dermoscopic recognition of amelanotic Spitz nevi is much more difficult. Dotted vessels, tan globules, and reticular depigmentation are common findings but the diagnosis should always be based on a combination of clinical and dermoscopic features.
Involution
After a growing phase of several months, the lesion starts to become smaller until it finally disappears. In conclusion, spontaneous involution seems to be by far the most common biologic behavior of both pigmented and nonpigmented Spitz nevi.
