Skin Biopsy
Definition
A skin biopsy is a procedure in which a small piece of living skin is removed from the body for examination, usually under a microscope, to establish a precise diagnosis. Skin biopsies are usually brief, straightforward procedures performed by a skin specialist (dermatologist) or family physician.
Purpose
The word biopsy is taken from Greek words that mean "to view life." The term describes what a specialist in identifying diseases (pathologist) does with tissue obtained from a skin biopsy. The pathologist visually examines the tissue under a microscope.
A skin biopsy is used to make a diagnosis of many skin disorders. Information from the biopsy also helps the doctor choose the best treatment for the patient.
Doctors perform skin biopsies to:
- make a diagnosis
- confirm a diagnosis made from the patient's medical history and a physical examination
- check whether a treatment prescribed for a previously diagnosed condition is working
- check the edges of tissue removed with a tumor to make certain it contains all the diseased tissue
Skin biopsies also can serve a therapeutic purpose. Many skin abnormalities (lesions) can be removed completely during the biopsy procedure.
Precautions
A patient taking aspirin or another blood thinner (anticoagulant) may be asked to stop taking them a week or more before the skin biopsy. This adjustment in medication will prevent excessive bleeding during the procedure and allow for normal blood clotting.
Some patients are allergic to lidocaine, the numbing agent most frequently used during a skin biopsy. The doctor can usually substitute another anesthetic agent.
Description
The first part of the skin biopsy test is obtaining a sample of tissue that best represents the lesion being evaluated. Many biopsy techniques are available. The choice of technique and precise location from which to take the biopsy material are determined by factors such as the type and shape of the lesion. Biopsies can be classified as excisional or incisional. In excisional biopsy, the lesion is completely removed; in incisional biopsy, a portion of the lesion is removed.
The most common biopsy techniques are:
- Shave biopsy. A scalpel or razor blade is used to shave off a thin layer of the lesion parallel to the skin.
- Punch biopsy. A small cylindrical punch is screwed into the lesion through the full thickness of the skin and a plug of tissue is removed. A stitch or two may be needed to close the wound.
- Scalpel biopsy. A scalpel is used to make a standard surgical incision or excision to remove tissue. This technique is most often used for large or deep lesions. The wound is closed with stitches.
- Scissors biopsy. Scissors are used to snip off surface (superficial) skin growths and lesions that grow from a stem or column of tissue. Such growths are sometimes seen on the eyelids or neck.
After the biopsy tissue is removed, bleeding may be controlled by applying pressure or by burning with electricity or chemicals. Antibiotics often are applied to the wound to prevent infection. Stitches may be placed in the wound, or the wound may be bandaged and allowed to heal on its own.
The second part of the skin biopsy test is handling and examining the tissue sample. Drying and structural damage to the tissue sample must be prevented, so it should be placed immediately in an appropriate preservative, such as formaldehyde.
The pathologist can use a variety of laboratory techniques to process the biopsy tissue. Tissue stains and several different kinds of microscopes are used. Because there are many skin disorders (broadly called dermatosis and dermatitis), the pathologist has extensive training in their accurate identification. Cases of melanoma, the most malignant kind of skin cancer, have almost tripled in the past 30 years. Because melanoma grows very rapidly in the skin, quick and accurate diagnosis is important.
Preparation
The area of the biopsy is cleansed thoroughly with alcohol or a disinfectant containing iodine. Sterile cloths (drapes) may be positioned, and a local anesthetic, usually lidocaine, is injected into the skin near the lesion. Sometimes the anesthetic contains epinephrine, a drug that helps reduce bleeding during the biopsy. Sterile gloves and surgical instruments are always used to reduce the risk of infection.
Aftercare
If stitches have been placed, they should be kept clean and dry until removed. Stitches are usually removed five to 10 days after the biopsy. Sometimes the patient is instructed to put protective ointment on the stitches before showering. Wounds that have not been stitched should be cleaned with soap and water daily until they heal. Adhesive strips should be left in place for two to three weeks. Pain medications usually are not necessary.
Risks
Infection and bleeding occur rarely after skin biopsy. If the skin biopsy may leave a scar, the patient usually is asked to give informed consent before the test.
Normal results
The biopsy reveals normal skin layers.
Key terms
Benign — Noncancerous.
Dermatitis — A skin disorder that causes inflammation, that is, redness, swelling, heat, and pain.
Dermatologist — A doctor who specializes in skin care and treatment.
Dermatosis — A noninflammatory skin disorder.
Lesion — An area of abnormal or injured skin.
Malignant — Cancerous.
Pathologist — A person who specializes in studying diseases. In particular, this person examines the structural and functional changes in the tissues and organs of the body that are caused by disease or that cause disease themselves.
Abnormal results
The biopsy reveals a noncancerous (benign) or cancerous (malignant) lesion. Benign lesions may require treatment.
Resources
Organizations
American Academy of Dermatology. 930 N. Meacham Road, P.O. Box 4014, Schaumburg, IL 60168-4014. (847) 330-0230. Fax: (847) 330-0050. http://www.aad.org.
skin
the outer covering and largest organ of the body. It serves as a protective barrier against microorganisms, helps shield delicate tissues underneath from mechanical and other injuries, insulates against heat and cold, and helps eliminate body wastes. It guards against ultraviolet radiation by producing a protective pigment and it helps produce vitamin D. Its sense receptors detect pain, cold, heat, touch and pressure.
The skin consists of an outer cellular, avascular epidermis, and an inner fibrous corium (dermis, true skin) resting upon a hypodermis of fat and panniculus muscle.
See also cutaneous, epidermal, epidermis.
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Basic structure of the skin. By permission from McCurnin D, Poffenbarger EM, Small Animal Physical Diagnosis and Clinical Procedures, Saunders, 1991
skin appendages
skin-associated lymphoid tissues (SALT)
see skin-associated lymphoid tissue.
autoimmune skin disease
skin biopsy
removal of a small section of skin for histopathological examination. See also keyes punch.
skin cancer
include squamous cell carcinoma, papilloma and fibropapilloma, intracutaneous cornifying epithelioma (keratoacanthoma), basal cell tumors and tumors of the adnexa, perianal gland and hair follicles.
congenital absence of skin
see epitheliogenesis imperfecta.
skin depigmentation
see hypopigmentation.
skin emphysema
see subcutaneous emphysema.
skin fold thickness
a measure of obesity in humans but not a valid indicator in dogs or cats as the skin lifts off the subcutaneous tissue.
skin fungal infection
skin gangrene
death of tissue and usually involves dermis, epidermis and subcutaneous tissue, e.g. severe saddle galls, heat burns, chemical burns, Claviceps purpurea poisoning. The affected area is cold and bluish in color. This changes to black and the area begins to lift at the edges and to dry out.
skin inflammation
see dermatitis.
skin leukosis
occurs in marek's disease. Called also cutaneous lymphosarcoma.
skin-maggot fly
see cordylobiaanthropophaga.
skin memory
see mnemodermia.
skin receptor
cutaneous sensory endorgans.
skin resiliency test
see skin tenting test (below).
skin tag
see fibrovascular papilloma.
skin tension lines
see tension line.
skin tenting test
a fold of skin is picked up and then quickly let go. The amount that it will stretch is an indication of its extensibility. The speed with which it returns to a normal position is determined by the degree of hydration of the skin and subcutaneous tissue and the amount of fat in the subcutaneous tissue, e.g. in an animal that is 10 to 12% dehydrated the skin fold will not disappear until 20 to 45 seconds have elapsed.
)
Tenting of the skin in a dehydrated cow. By permission from Blowey RW, Weaver AD, Diseases and Disorders of Cattle, Mosby, 1997
skin test
application or intradermal injection of a substance to the skin to test the body's reaction to it. Such a test detects an animal's sensitivity to such allergens as dust and pollen, or to preparations of microorganisms believed to be the cause of a disorder.
There are several types of skin tests, including the patch test, the scratch test, and the intradermal test.
skin wool
scoured wool from a fellmonger.
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