Skin Biopsy

Skin biopsy is the removal of a small piece of tissue under local anesthesia from a lesion suspected of being malignant or from other dermatoses. One of three techniques may be used: shave biopsy, punch biopsy, or excisional biopsy. Shave biopsy uses a scalpel to slice a superficial specimen from the site. Punch biopsy removes an oval core from the center of a lesion down to the dermis or subcutaneous tissue. Excisional biopsy removes the entire lesion with a small border of normal skin.

Lesions suspected of being malignant usually have changed color, size, or appearance or fail to heal properly after injury. Fully developed lesions should be selected for biopsy whenever possible because they provide more diagnostic information than lesions that are resolving or in early developing stages.

Purpose

• To provide differential diagnosis among basal cell carcinoma, squamous cell carcinoma, malignant melanoma, and benigngrowths.
• To diagnose chronic bacterial or fungal skin infections

Patient preparation

• Explain to the patient that the biopsy provides a specimen for microscopic study.
• Describe the procedure to the patient, and answer any questions.
• Inform him that he needn't restrict food or fluids.
• Tell him who will perform the procedure and where.
• Have the patient or an appropriate family member sign an informed consent form.
• Check the patient's history for hypersensitivity to the local anesthetic.

Procedure and posttest care

• Position the patient comfortably, and clean the biopsy site before the local anesthetic is administered.

Shave biopsy

• The protruding growth is cut off at the skin line with a #15 scalpel and the tissue is placed immediately in a properly labeled specimen bottle containing 10% formaldehyde solution.
• Apply pressure to the area to stop the bleeding.

Punch biopsy

• The skin surrounding the lesion is pulled taut, and the punch is firmly introduced into the lesion and rotated to obtain a tissue specimen. The plug is lifted with forceps or a needle and severed as deeply into the fat layer as possible.
• The specimen is placed in a properly labeled specimen bottle containing
  10% formaldehyde solution or in a sterile container, if indicated.
• Closing the wound depends on the size of the punch: A 3-mm punch requires only an adhesive bandage, a 4-mm punch requires one suture, and a 6-mm punch requires two sutures.

Excisional biopsy

• A #15 scalpel is used to excise the entire lesion; the elliptical incision is made as wide and as deep as necessary and includes a margin of apparently normal skin.
• The tissue specimen is removed and placed immediately in a properly labeled specimen bottle containing 10% formaldehyde solution.
• Apply pressure to the site to stop the bleeding.
• The wound is closed using 4-0 suture. If the incision is large, skin graft may be required.

All procedures

• Check the biopsy site for bleeding.
• If the patient experiences pain, administer an analgesic.
• Advise the patient with sutures to keep the area as clean and dry as possible. Facial sutures are removed in 3 to 5 days; trunk sutures, in 7 to 14 days. Tell the patient with adhesive strips to leave them in place for 14 to 21 days.

Precautions

• Send the specimen to the laboratory immediately.

Normal findings

Normal skin consists of squamous epithelium (epidermis) and fibrous connective tissue (dermis).

Abnormal findings

Histologic examination of the tissue specimen may reveal a benign or malignant lesion. Benign growths include cysts, seborrheic keratoses, warts, pigmented nevi (moles), keloids, dermatofibromas, and multiple neurofibromas.

Malignant tumors include basal cell carcinoma, squamous cell carcinoma, and malignant melanoma. Basal cell carcinoma occurs on hair-bearing skin; the most common location is the face, including the nose and its folds. Squamous cell carcinoma most often appears on the lips, mouth, and genitalia. Malignant melanoma, the deadliest skin cancer, can spread through the body by way of the lymphatic system and blood.

Cultures can be used to detect chronic bacterial and fungal infections in which flora are relatively sparse.

Interfering factors

• Improper selection of the biopsy site
• Failure to use the appropriate fixative or a sterile container
• Failure to send the specimen to the laboratory immediately