Nail Biopsy: Indications and Methods

Abstract

Nail biopsy is a safe and useful diagnostic procedure for many nail disorders when routine clinical and laboratory methods fail to produce a diagnosis. Prerequisites for nail biopsy are an understanding of the surgical anatomy of the nail, adequate anesthesia and hemostasis, and a nail abnormality for which histopathology can provide the diagnosis. Indications and methods for nail biopsy vary according to the site and type of pathology in the nail unit. Nail bed and perionychial biopsies can be performed easily and with minimal scarring. They are most commonly used to diagnose tumors as well as infectious and inflammatory disorders of the nail. The most important reason to biopsy the nail matrix is to make or exclude the diagnosis of melanoma in a patient with longitudinal melanonychia. Great care must be taken in nail matrix biopsy to minimize the risk of permanent nail dystrophy.

Nail matrix biopsy of longitudinal melanonychia: Diagnostic algorithm including the matrix shave biopsy

“…Traditional teachings suggest that matrix punch biopsies, 3 mm or less, are unlikely to cause a permanent dystrophy and that larger specimens are removed in a transverse orientation to facilitate repair and avoid dystrophic nail plate scarring. 1,2 More specifically, however, only 3-mm biopsies from the distal matrix are truly safe from permanent nail dystrophy; the proximal matrix, responsible for a majority of the nail plate production as well as the superficial nail plate, 3,4 is more susceptible to scarring or developing a split nail, even with a 3-mm punch. 2,5 Laterally based LM may be excised with lateral longitudinal excisions.…”

“…1,2 More specifically, however, only 3-mm biopsies from the distal matrix are truly safe from permanent nail dystrophy; the proximal matrix, responsible for a majority of the nail plate production as well as the superficial nail plate, 3,4 is more susceptible to scarring or developing a split nail, even with a 3-mm punch. 2,5 Laterally based LM may be excised with lateral longitudinal excisions. 6,7 This procedure is more invasive than a punch biopsy, is more technically demanding, and has more potential for complications, including acquired malalignment 8 and postoperative cyst or spicule formation.…”

“…Traditionally, transversely oriented curvilinear or elliptical excisions in the matrix are used for these biopsies. 2,11 These are technically more challenging and often require undermining and more demanding tissue reapproximation of the friable matrix. 2,10 Others recommend longitudinal matrix excisions for narrow bands and have demonstrated excellent results.…”

“…More challenging clinical scenarios involve LM originating in the proximal matrix or LM wider than 3 mm located medial to the lateral matrix. A 3-mm punch into the proximal matrix has the potential to cause a permanent nail dystrophy 2,10 or may result in a partial, incisional biopsy in the setting of a band wider than 3 mm, risking a false-negative result. Furthermore, multiple 3-mm punch biopsies in the setting of a wide pigmented band may increase the likelihood of permanent nail scarring and still may not completely sample the entire lesion.…”

“…2,5 Laterally based LM may be excised with lateral longitudinal excisions. 6,7 This procedure is more invasive than a punch biopsy, is more technically demanding, and has more potential for complications, including acquired malalignment 8 and postoperative cyst or spicule formation. 9,10 Other techniques have been elegantly described, including longitudinal matrix excision and total nail unit ''en bloc excision'' and are excellent resources for those interested in pursuing more advanced nail surgery.…”