Atlas of Procedures in Neonatology, 4th Edition
Punch Skin Biopsy
- A small, full-thickness biopsy utilizing a cylindrical instrument
- Diagnosis of skin lesions (1,2,3,4,5,6,7 and 8)
- Electron and light microscopic identification of certain hereditary and metabolic disorders (9,10,11,12,13,14 and 15)
- Genetic, enzymatic, or morphologic studies on established fibroblast strains (16)
- Treatment of small skin lesions
- Types of Skin Biopsy (6,10,17)
- Punch skin biopsy is appropriate when full thickness is necessary.
- Allows for pathologic evaluation and rapid diagnosis of certain conditions
- Incisional biopsies are used predominantly for disorders of deep subcutaneous fat or fascia (e.g., erythema nodosum).
- Excision of larger lesions by a trained dermatologist or surgeon is preferable when planning to remove an entire large lesion.
Bleeding disorder when risk outweighs benefits
- Towel or tray to form sterile area
- 70% alcohol or other suitable antiseptic agent
- 4- x 4-in gauze squares
- Lidocaine HCl 1% with epinephrine in 1-mL tuberculin syringe with 27- or 30-gauge needle (use epinephrine-free local anesthesia on extremeties to avoid distorting skin vascularity in patients with urticaria pigmentosa)
- Blunt tissue forceps
- Fine, curved scissors or no. 15 scalpel blade
- Sharp 3- or 4-mm punch1(Fig. 22.1)
Skin biopsy has been performed on the fetus (11,18) and may be done postmortem on stillborn or recently deceased infants to produce fibroblast cultures for karyotype (see Chapter 24). Under the latter circumstances, punch or excisional biopsy from the freshest-appearing, least-macerated skin area(s) is appropriate.
- 5-0 or 6-0 nylon suture with small curved needle on needle holder, Dermabond (Ethicon, Somerville, NJ, USA) or Steri-Strip (3M Health Care, St. Paul, MN, USA)
- Adhesive bandage with petrolatum jelly
- Appropriate transport medium affixed with patient's information (Table 22.1) (In addition, a razor may be required for hairy areas)
- Avoid sites, if possible, where a small scar would potentially be cosmetically disfiguring.
- Tip, bridge, and columella of nose
- Lip margins
- Fingers or toes
- Areas overlying joints
- Lower leg below the knee
- Avoid very small punch (2 mm or less), because this limits ability to interpret pathologic findings.
- Avoid multiple procedures to one site.
- Be gentle, to avoid separating epidermis from dermis.
- Check biopsy site for signs of infection until healing occurs.
- Avoid freezing tissue for electron microscopy because cellular detail will then be destroyed (Table 22.1).
- For specimens undergoing routine microscopic examination, avoid placing biopsy specimen in or on saline because artifactual hydropic degeneration of basal cells and subepidermal bullous formation may occur.
FIG. 22.1. Punch skin biopsy. Top (inset): Disposable biopsy punch. Bottom (inset): Cutting the dermal pedicle.
- Technique (6,8,17,19,20)
See Fig. 22.1.
- Restrain and position patient.
- Choose site for biopsy.
- For suspected malignant lesions, choose more atypical areas if unable to excise completely.
- For large or chronic lesions, obtain specimen from periphery, including some normal skin.
- For most dermatoses, choose site of early or fully developed, but not end-stage, lesion.
- For acute eruptions and bullous disease, choose an early lesion, including some normal skin.
- For discrete small lesions, try to leave 1- to 2-mm margins of normal skin around the lesions.
- Avoid excoriated, crusted, or traumatized lesions.
- Shave skin, if necessary.
- Prepare as for minor procedure (see Chapter 4).
- Inject 0.25 to 0.5 mL of lidocaine (with/without epinephrine) intradermally beneath the lesion.
- Wait 5 minutes.
- Stretch skin surrounding lesion taut.
- Carefully place punch over the lesion and twist in rotary back-and-forth cutting motion until subcutaneous fat is obtained. Biopsy should include epidermis, full thickness of dermis, and some subcutaneous fat.
- Remove punch.
- Use blunt forceps in one hand to grasp the lateral edge of the biopsy specimen and elevate it, utilizing care to avoid crush artifact.
- Use scalpel blade or scissors in the other hand to cut the punch specimen at its base, as deep into the subcutaneous fat tissue as possible.
- Place specimen in container with appropriate preservative or transport medium.
- Label container with patient name, date, and exact site of biopsy.
- Control bleeding at site of biopsy with gentle pressure on sterile 4- x 4-in gauze square.
- Approximate wound margins and apply Dermabond. No further care is required.
- If suture or Steri-Strips are placed, leave for 5 days on face and for 12 days on trunk, limbs, or scalp.
- Although not recommended by the author, some practitioners allow the wound to heal by secondary intention. If no suture is placed, expect healing by primary epithelialization in 7 to 14 days, with a residual white area a few millimeters in diameter if the biopsy extended to the dermisâ€“subcutaneous fat interface.
TABLE 22.1 Punch Biopsy Preservatives and Transport Media
- Complications (6)
- Unsightly scarring or keloid formation (rare)
- Excessive bleeding (rare, except in patient with coagulation defect)
- Pathologic uncertainty
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- Martin J, Jacobs K.Skin biopsy as a contribution to diagnosis in late infantile amaurotic idiocy with curvilinear bodies. Eur Neurol.1973;10:281.
- O'Brien J, Bernet J, Veath M, Paa D.Lysosomal storage disorders: diagnosis by ultrastructural examination of skin biopsy specimens. Arch Neurol. 1975;32:592.
- Spicer S, Garvin A, Wohltmann H, et al. The ultrastructure of the skin in patients with mucopolysaccharidoses. Lab Invest.1974;31:488.
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- Golbus M, Sagebiel R, Filly R, et al. Prenatal diagnosis of ichthyosiform erythroderma (epidermolytic hyperkeratosis) by fetal skin biopsy. N Engl J Med.1980;302:93.
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- Ruiz-Maldonado R, Parish LC, Beare JM.Therapeutic aspects of pediatric dermatology. In: Ruiz-Maldonado R, Parish LC, Beare JM, eds. Textbook of Pediatric Dermatology. Philadelphia: Grune & Stratton; 1989:50.