Gouty Tophi: A Squamous Cell Carcinoma Mimicker?

BACKGROUND: Digital lesions can have a broad differential diagnosis. Squamous cell carcinoma (SCC), the most common digital malignant neoplasm, must be excluded as the cause of persistent digital lesions causing nail dystrophy. OBJECTIVE: To describe a patient with a periungual hyperkeratotic lesion on the left fifth digit which, upon initial dermatopathologic examination, appeared to be a malignancy. However, on further biopsy, the lesion proved to be a gouty tophus. METHODS: Case report and literature review. RESULTS: An 84-year-old white man presented with a hyperkeratotic papule on the lateral proximal nail fold of the left fifth digit, which resulted in nail dystrophy for 1 year. Similar lesions were present on several other digits which did not affect the nail plate. Initial biopsy was consistent with actinic keratosis and was treated with cryotherapy. When the lesion persisted, repeat biopsy was performed, demonstrating fragments of squamous epithelium with focal atypia and an infiltrative growth pattern. SCC could not be excluded and the patient was referred for Mohs micrographic surgery (MMS) consultation. An excisional biopsy was performed and a white chalky material was observed at the base of the defect. Histopathology confirmed a gouty tophus. The patient was referred to his primary care physician and was treated with allopurinol. CONCLUSION: This is the first report of gouty tophus of the periungual region presenting as a hyperkeratotic lesion. Initial clinical diagnosis favored SCC and histologic evidence suggested a possible early SCC. This lesion can be confused with digital squamous cell carcinoma. The presence of pseu- docarcinomatous hyperplasia may complicate accurate diagnosis.