Nail biopsy
Nail biopsy
The main indications for nail biopsies are inflammatory nail disorders restricted to the nails, longitudinal melanonychia, and nail tumors. Different types of biopsies can be performed (Fig. 23.2).4,5
1130 Diseases of the nails
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2 3 4
2 Matrix Nail bed H
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4 5
Prior to cutting, the blocks are placed in KOH for 30 minutes and in a solution of detergent and ammonia for 20 minutes.1 Five percent trichloroacetic acid in 10% formalin, 5% trichloroacetic acid with a modification of the water-soluble Carbowax embedding method, ‘chitin softening solution’, and softening in cedar oil have also been suggested.1
• The sample needs to be correctly oriented. We usually try to perform sections parallel to the longitudinal axis of the nail. Lateral longitudinal biopsies are cut, starting from the central part of the nail and progressing toward the skin side. Three- to four-millimeter punch biopsies are embedded as such (without having been previously cut in two). A few sections are first made. If they are correctly oriented, other sections are performed. For nail biopsies, multiple sections are systematically performed.
• Special stainings and immunohistochemistry are often necessary.
• The longitudinal nail biopsy allows examination of all the nail apparatus components, but leaves a slightly narrowed nail (Fig. 23.3).
• Matrix biopsies should preferably be taken after partial nail plate avulsion. A 3-mm punch biopsy is the most frequently used. Transverse crescentic biopsies are also sometimes obtained. The more recently described matrix shave biopsy is mainly used for longitudinal melanonychia.6,7
• In the nail bed, a 3- to 4-mm punch biopsy or a longitudinal elliptic biopsy are the most frequently employed.
• Distal nail plate samples, which are easily obtained with nail clippers, can be used for the diagnosis of onychomycosis.8
Fig. 23.1 Normal nail: proximal nail fold (1), cuticle (2), lunula (3), nail plate (4), distal nail groove (5), hyponychium (H). The small dots represent the stratum granulosum.
Fig. 23.2 Nail biopsies: lateral-longitudinal biopsy (1), punch and transverse crescentic matrix biopsies (2), punch and longitudinal elliptic nail bed biopsies (3).
Fig. 23.3 Nail: lateral longitudinal biopsy. Courtesy of B. Richert, MD, PhD, Université Libre de Bruxelles, Belgium.