Dermoscopy of Atypical Nevi
There are several variations of Clark nevi. One must understand and recognize these variations in order to differentiate these lesions from melanoma. There are limitation in the ability of dermoscopy and physical examination to differentiate between Clark nevi and melanoma in situ or early invasive melanoma.
A paper entitled Dermoscopic Classification of Atypical Melanocytic Nevi (Clark Nevi) was published in the Archives of dermatology in 2001. The classification is easily applicable because only 3 dermoscopic structural features (reticular, globular, homogeneous) and 2 descriptors of pigmentation have to be identified. The homogeneous pigmentation is either dark (hyperpigmentation) or light (hypopigmenation). Pigmentation can appear in different distribution patterns.
Classification is therefore by predominate structural component and distribution of pigmentation. The three dermoscopic structural types are reticular, globular, and homogeneous. Two structural components may be present in a single lesion. This results in 6 dermoscopic subtypes: reticular, globular, homogeneous, reticular-globular, reticular-homogeneous, and globular-homogeneous. The most common type of atypical nevus is the reticular type, followed by the reticular-homogeneous and globular-homogeneous types. No more that three structural components are present in benign atypical nevi.
In addition, Clark nevi are classified by pigmentation distribution into 3 groups. Nevi with uniform pigmentation, nevi with multifocal hyperpigmentation or hypopigmentation, and nevi with central or eccentric hyperpigmentation or hypopigmentation.