Dermatology Online Journal

Histopathology of the Nail
Emily F. Omura MD
Dermatology Online Journal 7(1): 23E

---

Indications for nail biopsy include disease confined to the nails, a potentially scarring condition, to confirm a fungal infection before oral therapy, and to diagnose a malignancy. Good communication between surgeon and pathologist is essential for correct orientation and interpretation of the specimen. Methods for softening the hard keratin of the nail plate for cutting, and for increasing adherence to the glass slide, are described. Nail specimens are received most often as clippings to confirm a fungal infection. Hyphae and spores are usually seen in the lower portion of the nail plate, explaining the difficulty of getting positive KOH preparations or cultures from the nail surface. PAS stain should always be done on nail specimens. The most important reason for nail biopsy is to diagnose a tumor. The "red flag" should appear when a single nail is involved and when the problem is of long duration. Subungual squamous cell carcinoma, keratoacanthoma, verruca, and fibrokeratoma, glomus tumor, and osteochondroma are described, but melanoma is the disease in which a delay in diagnosis, due to reluctance to biopsy the nail or to an inadequate specimen, may have the worst consequences for the patient. The histologic features of subungual melanoma are shown. Some diseases may occur in nails alone, including psoriasis and lichen planus. Biopsies of these conditions, plus Darier disease, sarcoid, myxoid cyst, Langerhans cell histiocytosis, and Pseudomonas infection are described.

© 2001 Dermatology Online Journal