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.

Disadvantages

• Excisional if lesion small enough, or incisional.
• 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 lignocaine    with adrenaline near extremities and into patients with circulatory disorders (maximum 1ml of 2% lignocaine/5kg body weight).
• Select primary lesions if possible.

Requirements

Materials required

Minimum equipment

• Sterile surgical instruments.

Minimum consumables

• Local anesthetic (1-2% lidocaine    ) preferably without adrenaline.
  Adrenaline can cause histological artifacts in vasculature.
• 25G needles and syringe.
• Scalpel blade or 4-8mm biopsy punch.
• Suture material.
• Small-toothed forceps or 25g needle.
• Wooden tongue depressors or cardboard.
• 10% neutral buffered formalin.
• Special fixative may be required eg Michel's fixature for immunofluorescence testing.

Preparation

• 5-20 minutes.

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 particularly if injected near extremities and into patients with circulatory disorders (maximum 1ml of 2% lidocaine/5kg body weight).

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

• Noxon J O (1995) Diagnostic procedures in feline dermatology.Vet Clin North Am Small Anim Pract. 25 (4), 779-799.