Subungual epidermoid carcinoma.

Subungual Bowen's disease and squamous cell carcinoma are not as rare as has been implied by earlier literature. The course of the lesions is protracted. Clinically the diseases may mimic onychomycosis, chronic paronychia, eczema, verruca vulgaris, pyogenic granuloma, subungual exostosis, or malignant melanoma. Histologic examination is the key to diagnosis. As only two metastases have occurred in 110 patients, subungual epidermoid carcinomas should be regarded as low-grade malignancies that can be managed by conservative surgical ablation. The microscopically controlled excision technic (Mohs chemosurgery) is ideal for these tumors. Amputation of the affected digit is too drastic, especially when the thumb, the most common site, is involved.