A clinical mimicker of melanoma with distinctive histopathology: Topical silver nitrate exposure

Exposure to silver-containing compounds can result in reversible discoloration of the skin, presenting as an irregular brown or black macule, which can have a clinical appearance similar to melanoma. Both the clinical scenario and the histopathology are unique. Silver nitrate darkens with exposure to light, and the area can appear to change over time. On microscopic examination, there are coarse pigmented granules dispersed throughout the corneal layer, and largely absent from the remainder of the epidermis-although the precise location may depend on the duration of topical exposure. While argyria, its irreversible counterpart, has been well-characterized, only a single source has previously reported the histopathology of transient topical silver nitrate exposure. We present two cases, review the clinical and histopathologic differentials, and detail the distinctive histopathology that enables a diagnosis to be suggested in this clinical mimicker of melanoma.

Cutaneous deposits

: The cutaneous deposition disorders are a group of unrelated conditions characterized by the accumulation of either endogenous or exogenous substances within the skin. These cutaneous deposits are substances that are not normal constituents of the skin and are laid down usually in the dermis, but also in the subcutis, in a variety of different circumstances. There are 5 broad categories of cutaneous deposits. The first group includes calcium salts, bone, and cartilage. The second category includes the hyaline deposits that may be seen in the dermis in several metabolic disorders, such as amyloidosis, gout, porphyria, and lipoid proteinosis. The third category includes various pigments, heavy metals, and complex drug pigments. The fourth category, cutaneous implants, includes substances that are inserted into the skin for cosmetic purposes. The fifth category includes miscellaneous substances, such as oxalate crystals and fiberglass. In this article, the authors review the clinicopathologic characteristics of cutaneous deposition diseases, classify the different types of cutaneous deposits, and identify all the histopathologic features that may assist in diagnosing the origin of a cutaneous deposit.