Dermatology: biopsy skin

Introduction

• Skin histopathology is a valuable aid to differential and definitive diagnosis of many skin disorders.

Uses

• Definitive diagnosis of certain skin diseases.
• Categorization of skin disease.
• Exclusion of some diseases.

Advantages

• Provides useful information.

Disadvantages

• May not be diagnostic in all cases.
• Sutures, dehiscence.
• Most animals require sedation.
• Nasal, facial and footpad lesions: may require short-acting general anesthesia.
• Must be obtained early in course of disease before chronic inflammatory changes occur.
• Exercise caution if:
  • Bleeding disorders or concurrent medication, eg aspirin or anticoagulants affecting bleeding.
  • Immunosuppressed animals: rare (may be wound healing problem).
  • Local anesthesia : injecting lidocaine with adrenalin near extremities and into patients with circulatory disorders (maximum 1 ml of 2% lidocaine /5 kg bodyweight).

Preparation

• 5-20 min (depending on the site).

Requirements

Materials required

Minimum equipment

• Sterile surgical instruments.

Minimum consumables

• Local anesthetic (lidocaine ) preferably without adrenalin.
  Adrenalin can cause histological artifacts in vasculature.
• 25-gauge needles and syringe.
• Disposable biopsy punch, eg 6 mm.
• Scalpel blade or 4-8 mm biopsy punch.
• Suture material.
• Small-toothed forceps.
• Wooden tongue depressors or cardboard.
• 10% neutral buffered formalin for most samples. For some types of immunohistochemistry protocols, samples should be snap frozen rather than fixed in formalin.

Sequelae

Complications

• Rare.
• Hemorrhage in animals with bleeding disorders, taking aspirin or anticoagulants (stop 1-2 weeks before biopsy).
• Delayed wound healing in immunosuppressed patients + those on corticosteroids.
• Lidocaine toxicity particulary if injected near extremities and into patients with circulatory disorders (maximum 1 ml of 2% lidocaine/5 kg bodyweight).

Reasons for treatment failure

• Improper site selection.
• Improper preparation, eg surgical scrubbing.
• Intradermal local anesthetic injection.
• Shearing of specimen by blunt punch or poor technique.
• Squeeze artifacts due to crushing with forceps.
• Hemorrhage due to inadequate blotting can obscure pathologist's view of tissue.
• Dehydration due to drying in air: specimen must be placed in formalin within 1-2 minutes.
• Shrinkage, curling and folding due to failure to use wooden or cardboard splints.
• Freezing.

Sources

Publications

• Recent references from PubMed.
• Rizzo L B, Ritchey J W, Higbee R G, Bartels K E & Lucroy M D (2004) Histologic comparison of skin biopsy specimens collected by use of carbon dioxide or 810-nm diode lasers from dogs. JAVMA 225 (10), 1562-1566 PMID.