127

Manju Dawkins

23 Punch Skin Biopsy

A. Definition

1. A small, full-thickness biopsy utilizing a cylindrical

instrument

B. Indications

1. Diagnosis of skin lesions (1–8)

2. Electron and light microscopic identification of certain

hereditary and metabolic disorders (9–15)

3. Genetic, enzymatic, or morphologic studies on established fibroblast strains (16)

4. Treatment of small skin lesions

C. Types of Skin Biopsy (6,10,17)

1. Punch skin biopsy is appropriate when epidermis, dermis, and, sometimes, subcutaneous fat is required.

 Allows for pathologic evaluation and rapid diagnosis

of certain conditions

2. Shave biopsies are performed to obtain epidermis and

superficial dermis.

3. Incisional biopsies are used predominantly for disorders of

deep subcutaneous fat or fascia (e.g., erythema nodosum).

4. Excision of larger lesions by a trained dermatologist or

surgeon is preferable when planning to remove an entire

large lesion.

D. Contraindications

There are no absolute contraindications to skin biopsy.

1. Consider whether risk outweighs benefit if a bleeding

disorder is present.

2. Caution should be exercised in certain anatomic

locations where nerves and arteries are more superficial.

3. Many cephalic and midline lesions may require

radiologic examination prior to biopsy to rule out

connection to the intracranial or intraspinal space

(18,19).

E. Equipment

Sterile

1. Gloves

2. Towel or tray to form sterile area

3. 70% alcohol or other suitable antiseptic agent

4. 4- × 4-in gauze squares

5. Lidocaine HCl 1% with or without epinephrine in

1-mL tuberculin syringe with 27- or 30-gauge needle

6. Blunt tissue forceps

7. Fine, curved scissors or no. 15 scalpel blade

8. Sharp 2- to 6-mm punch (Fig. 23.1). Disposable

punches ranging from 2 to 8 mm are available

 Specimens obtained with a 2-mm punch are very

small and may not yield enough tissue for an accurate

diagnosis. One recent study showed that accurate diagnoses were achieved in 79 out of 84 cases, when comparing 2-mm punch biopsies to excisional specimens

(20). In most cases, a 3- to 4-mm punch is appropriate.

 Skin biopsy has been performed on the fetus

(11,21,22) and may be done postmortem on stillborn

or recently deceased infants to produce fibroblast cultures for karyotype (see Chapter 25). Under the latter

circumstances, punch or excisional biopsy from the

freshest-appearing, least-macerated skin area(s) is

appropriate.

9. 5-0 or 6-0 nylon suture with small curved needle on needle

holder, Dermabond (Ethicon, Somerville, New Jersey)

Nonsterile

1. Adhesive bandage with petrolatum jelly

2. Appropriate transport medium affixed with patient’s

information (Table 23.1)

3. Razor if necessary

F. Precautions

1. Avoid sites, if possible, where a small scar would potentially be cosmetically disfiguring.

a. Tip, bridge, and columella of nose

b. Eyelids

128 Section IV ■ Miscellaneous Sampling

c. Lip margins

d. Nipples

e. Fingers or toes

f. Areas overlying joints

g. Lower leg below the knee

2. Avoid a very small punch (2 mm or less), because this

may limit the ability to interpret pathologic findings.

3. Avoid multiple procedures at one site.

4. Be gentle, to avoid separating epidermis from dermis.

5. Check biopsy site for signs of infection until healing

occurs.

6. Avoid freezing tissue for electron microscopy because

cellular detail will then be destroyed (Table 23.1).

7. 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.

G. Technique (6,8,17,23,24)

See Fig. 23.1.