Contributors: Rosanna Marsella, Irene Rochlitz, David Scarff

 Species: Feline   |   Classification: Techniques

Introduction Requirements Preparation Procedure Aftercare Outcomes Further Reading


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


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


  • 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 Lidocaine with adrenaline near extremities and into patients with circulatory disorders (maximum 1ml of 2% lignocaine/5kg body weight).
  • Select primary lesions if possible.

Technical Problems

  • Artifacts may cause difficulty in interpretation.
  • Representative tissue must be submitted.

Time Required


  • 5-20 minutes.


  • 5-20 minutes.

Decision Taking

Criteria for choosing test

  • Primary lesions.
  • Deep lesions.
  • Masses or any possible neoplastic lesions.
  • Non-healing lesions.
  • Conditions failing to respond to therapy (generally within 3 weeks).
  • Unusual or atypical dermatoses.
  • Conditions suspected which require therapy which may be expensive, of extended duration or hazardous.
  • Dermatosis diagnosed by biopsy, eg immune-mediated skin disease .
    Stop topical or systemic glucocorticoid therapy 2-4 weeks before biopsy.If secondary bacterial pyoderma Bacterial skin disease: overviewadminister course of systemic antibiotic therapy before biopsy.

Risk assessment

  • Sedation or general anesthesia: routine checks
  • If known bleeding disorder: caution.



Other involvement

  • Veterinary specialist dermatohistopathologist.

Materials Required

Minimum equipment

  • Sterile surgical instruments.

Minimum consumables

  • Local anesthetic (1-2% lidocaine 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.


Site Preparation

  • Select primary lesions (macules, papules, pustules, vesicles, bullae, nodule and tumors).
  • Avoid excoriated sites.
  • Clip hair very gently, if necessary.
    Do not cleanse or prepare site in any way.


Either Assistant holding.
Or Sedation and assistant holding.
Or General anesthesia.
Cats will almost always require general anesthesia or profound sedation.



Step 1 - Select site

  • For wedge biopsy - biopsy at junction of normal and abnormal skin; ensure wedge orientation is correct.
    The lesion should be at one pole of ellipse and normal tissue at other because samples are cut longitudinally during processing.
  • For punch biopsy sample lesional tissue and 'normal' skin separately.

Step 2 - Marking site

  • Mark site of biopsy with indelible marker to prevent inadvertent sampling of non-blocked areas.
  • Place 4 dots equidistant from site or encircle site.

Step 3 - Local anesthesia

  • Using a syringe with 25G needle, introduce lidocaine 2% into subcutaneous tissue directly beneath lesion.

Step 4 -

  • For minimal patient discomfort, gently reposition the needle (without removing it) to deposit anesthetic in fan-like pattern.

Step 5 -

1 ml of lidocaine per site is adequate; maximum 1ml/5 kg body weight.
  • Wait 5-8 minutes before performing biopsy.

Core Procedure

Step 1 - Punch biopsy

  • Place punch directly over lesion to be sampled.
  • Rotate gently in one direction while exerting gentle downwards pressure.
    Do not rotate back and forth because this may cause sample damage by shearing forces.
  • Continue until punch 'drops' into subcutaneous tissue  Skin: punch biopsy 01 .
  • Use 25g needle to raise sample from site.
  • Use scalpel blade to cut sample plug from small pedicle of subcutaneous tissue and fat to which it is attached.

Step 2 - Wedge biopsy

  • Excise ellipse of tissue using a surgical blade.
  • Do not exceed 2cm in width or length because larger specimens may not fix adequately.
  • Grasp one end with forceps when freeing section from subcutaneous tissues.

Step 3 - Specimen preservation

  • Gently remove specimen with a pair of small toothed forceps or mosquito hemostats.
  • Grasp only by hair stubble, subcutaneous fat or edge of dermal-epidermal junction.
    Excessive manipulation can make specimen useless.
  • Blot excess blood.
  • Place subcutaneous side of biopsy on small piece of tongue depressor or cardboard to prevent curling during fixation (wedge biopsy only)  Skin: punch biopsy 02  Skin: punch biopsy 03 .
  • Allow to stand for 30-60 seconds.
  • Place in 10% neutral buffered formalin as soon as biopsy has adhered, ensuring volume of fixative is at least x10 volume of sample.
  • Allow specimen to fix for 24 hours.
  • Special procedure if suspect mycobacterial skin disease: collect biopsy, cut into three pieces etc.


Step 1 - Suture biopsy site

  • Standard skin suturing technique.

Step 2 - End sample

  • Use specialist veterinary dermatohistopathologist.
  • Include details of history (including medication), clinical appearance, sites biopsied and differential diagnosis.



Antimicrobial therapy

  • Only if immunosuppressed animal.



  • 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

Poor biopsy sampling

  • 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.

Further Reading


Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Noxon J O (1995) Diagnostic procedures in feline dermatology. Vet Clin North Am Small Anim Pract 25 (4), 779-99 PubMed.

Other sources of information

  • Ihrke P J (1996) Bacterial Skin Disease in the Dog - a Guide to Canine Pyoderma. Veterinary Learning Systems. pp 59-61. (Biopsy technique with special reference to pyoderma.)
  • Ogilvie G K & Moore A S (1995) Managing the veterinary cancer patient: A practice manual. Veterinary learning systems pp6-8.
  • Moriello K A & Mason I S (1995) Eds Handbook of Small Animal Dermatology. 1st edn. Oxford: Pergamon. pp 31-33. (Step by step procedure with photographs.)
  • Muller G H et al (1995) Muller and Kirk's Small Animal Dermatology. 5th edn. Philadelphia: W B Saunders. pp 111-118. (Detailed account.)