Hypopigmentation refers to a localized or diffuse area of decreased pigmentation within an otherwise ordinary pigmented lesion. Localized hypopigmentation may be observed also in focal and multifocal variants.
The underlying histopathology of hypopigmentation is poorly understood, but obviously correlates with epidermal and dermal areas of decreased melanin pigmentation.
Like in pigmentation, the diagnostic significance of hypopigmentation is limited. The various kinds of hypopigmentation are commonly found within Clark nevi. In rare instances areas of irregularly outlined hypopigmentation may be observed also in melanomas.