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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.

A 29 year-old lady attended the Accident and Emergency Department of a District General Hospital complaining of increasing black discoloration of the tip of her left middle finger; the appearance resembled that of gangrene. However, it was established that she had been applying silver nitrate to her finger, as prescribed by her general practitioner for the treatment of a small granuloma. Hence, the true diagnosis was of localised tissue necrosis, secondary to application of the silver nitrate sticks. On early discontinuation of the therapy, there was complete recovery. In consequence, it is recommended that the practice of unsupervised local application of silver nitrate to the fingers should be discontinued. Opportunity is taken herein to review the uses of silver nitrate in clinical situations - and of silver in any of its many other forms - together with their respective adverse effects.