Nail pathology.

When dealing with nails, pathologic examination is often indispensable to reach an accurate diagnosis. This requires a biopsy correctly performed by the dermatologist, a specimen correctly handled in the pathology lab, and a pathologist with good knowledge of the various nail conditions. The normal nail histology is first described in this paper. The pathologic aspects of melanocytic lesions, nonmelanocytic tumors of the nail apparatus, inflammatory nail conditions, and onychomycosis are then considered, together with their main differential diagnoses.