Dermoscopy of Atypical Nevi Examples
The following four subtypes are distinctive and due to a specific distribution of hypopigmentation or hyperpigmentation throughout the lesion, namely, central, multifocal, or peripheral.
1. Atypical nevus with central hypopigmentation: This is a variant of the reticular type with a more or less centrally situated hypopigmented area and a reticular pattern surrounding the periphery.
2. Atypical nevus with central hyperpigmentation: This type is composed of a rim of prominent pigment network lines at the periphery and a central, diffuse, irregularly outlined black hyperpigmentation. This reticular-homogeneous type with central hyperpigmentation is also know as the hypermelanotic nevus.
3. Atypical nevus with multifocal hypo/hyperpigmentation: There are several, small, isolated hypopigmented areas, that leads to an uneven distribution of the pigment network. Patchy distribution of pigmentation, simulates the uneven pigmentation observed in melanoma. Atypical nevi with the reticular pattern and uneven pigmentation are especially prone to over diagnosis as melanoma.
4. Atypical nevus with peripheral hyperpigmentation: There is a reticular pattern with a prominent eccentric peripheral hyperpigmentation. Eccentric peripheral hyperpigmentation is also often found in malignant melanoma. Therefore atypical nevi with eccentric peripheral hyperpigmentation should be excised or monitored using dermoscopy at frequent intervals. When the eccentric peripheral hyperpigmentation increases, excision of the lesion is necessary.
A delicate vascular pattern characterized by the presence of comma and dotted vessels is often see in atypical nevi.
Most individuals have one predominant type of atypical nevus. Therefore a lesion that does not belong to the predominant type of atypical nevus in a given patient should be considered an atypical lesion and excised or examined frequently.