ABSTRACT
This chapter summarizes conditions typified clinically by hyperpigmentation that can be diagnosed by specific histopathologic changes. Some diseases with very similar histopathologies but diverse clinical findings have also been included to demonstrate the limitations of histopathological diagnosis. The chapter discusses various disorders of hyperpigmentation with their histopathological correlates according to the histological level of the pigmentary change. Pigmentation in the cornified layer may be caused by exogenous pigment, such as self-tanner or dirt; hyperkeratosis, like in terra firma-forme dermatosis. Self-tanners contain sugar molecules like dihydroxyacetone or erythrulose that react with proteins and amino acids of the cornified layer, leading to discoloration. Melanocytic neoplasms, both benign and malignant, may be covered by a heavily pigmented cornified layer. Dermatosis papulosa nigra is a condition seen on the face of patients with dark skin types. Various medications, such as antimalarial drugs, phenothiazines, tetracyclines, and minocycline, may induce pigmentary alterations.
