Nail Plate, Nail Bed, and Nail Matrix Biopsy

CHAPTER 28 Nail Plate, Nail Bed, and Nail Matrix Biopsy



Steven E. Roskos


Nail biopsy is a simple procedure that can be used to diagnose tumors, inflammatory diseases, and infections of the nail. Nail plate biopsy is the simplest of the nail biopsies and is useful for diagnosing proximal subungual onychomycosis as well as distinguishing melanoma from other types of nail pigmentation. Nail bed biopsy is helpful in diagnosing many disorders, including psoriasis, lichen planus, squamous cell carcinoma, melanoma, and subungual epidermoid inclusions. Nail matrix biopsy is used to distinguish between benign pigmented streaks (longitudinal melanonychia) and melanoma.


The presence of melanocytes in the germinal tissue of the nail matrix makes this a possible site for development of melanoma. Primary subungual melanomas frequently appear as pigmented bands or streaks in the nail plate, and they account for up to 3.5% of all cutaneous malignant melanomas (15% to 20% in blacks). Distinction between the numerous benign causes of pigmented streaks (trauma, malnutrition, and normal occurrence in many blacks and Asians) and malignant lesions is frequently difficult. Biopsy is often recommended to confirm the diagnosis.



Anatomy


The nail plate is the hard, translucent structure composed of keratinized squamous cells, commonly called the “nail” itself. The nail bed refers to the softer tissue beneath the nail that provides germinal tissue for the nail plate and to which the nail plate is attached (Fig. 28-1). The nail matrix lies beneath the proximal nail fold and synthesizes 90% of the nail plate.


image

Figure 28-1 Anatomy of the nail, dorsal view. Also shows possible shapes for obtaining a nail biopsy.



Indications



• Thickened, distorted nail plate with a negative evaluation for fungal infection (potassium hydroxide [KOH] scraping, culture)

• Longitudinal pigmented linear streak in the nail plate suspect for malignancy

• Tumor of the nail bed

• Subungual hyperkeratosis

• Diagnosis of disorders such as psoriasis and lichen planus


Contraindications



• Allergy or sensitivity to local anesthetics (see Chapter 4, Local Anesthesia)

• Bleeding diathesis or uncontrolled anticoagulation therapy (no need to stop warfarin, aspirin, or clopidogrel)


Equipment



• Antiseptic (chlorhexidine, povidone–iodine, or alcohol)

• Sterile gloves

• 3-mm disposable skin biopsy punch

• Local anesthetic (e.g., 1% or 2% lidocaine) without epinephrine

• 27-gauge needle (for toes) or 30-gauge needle (for fingers)

• Sterile scissors with straight blades (or a narrow Locke periosteal elevator)

• Sterile rubber band, small Penrose drain, or Ellman disposable digit tourniquet

• Two sterile, straight hemostats

• 5-0 or 6-0 nylon suture

• Needle driver

• No. 15 scalpel (for nail matrix biopsy)

• Fine sterile scissors with curved blades (for nail matrix biopsy)

• Steri-Strips (for nail matrix biopsy)

• Tissue forceps (for nail matrix biopsy)

• Xeroform gauze

• Sterile gauze and tubular gauze dressing

• Antibiotic ointment (Bacitracin or Polysporin)

• Adhesive bandage or an adhesive wrap like Coban or Co-Flex tape

• Suture scissors

• Sterile specimen container filled with 10% formalin (for histology)

• Sterile specimen container without formalin (for fungal culture)


Precautions


When sampling the nail matrix, be careful not to damage the proximal matrix. Most linear melanomas (95%) originate from the distal matrix. Biopsies of the distal nail matrix are very unlikely to produce permanent scarring because this part of the matrix produces the ventral portion of the nail plate. Biopsies of the proximal nail matrix will usually cause a permanent nail plate abnormality in the form of a longitudinal fissure. For pigmented streaks less than 3 mm wide, punch biopsy as described in this chapter is an adequate technique. Larger lesions require more extensive excision and are more likely to cause nail deformity.



Preprocedure Patient Education


It is important to explain to the patient what information you hope to gain from the biopsy and how it will affect treatment decisions. Explain that a biopsy is not guaranteed to produce an accurate diagnosis. Describe the procedure in detail, including the anesthesia. Make sure the patient understands the risks, which include bleeding, distortion of the nail during regrowth, infection, onycholysis (separation of nail from nail bed), permanent nail abnormality, and scarring. The patient should be given an opportunity to read the patient education handout and the consent form before signing it (see patient education and patient consent forms online at www.expertconsult.com).



Technique



Nail Plate (Nail) Biopsy



1 Soak the affected digit and nail in warm water for 10 minutes to soften the nail plate.

2 With steady pressure, hold the punch perpendicular to the nail; rotation of the punch will produce a round biopsy specimen without pain. No anesthetic is required.

3 Elevate the biopsy sample and lyse the underlying nail bed tissue with the scissors or scalpel.

4 Place the specimen in a sterile container if it is being sent for fungal culture, or a formalin-filled container if it is being sent for histology or periodic-acid Schiff (PAS) staining.


Nail Bed Biopsy



1 Soak the digit in warm water for 10 minutes to soften the nail plate.

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May 14, 2017 | Posted by in GENERAL & FAMILY MEDICINE | Comments Off on Nail Plate, Nail Bed, and Nail Matrix Biopsy

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