SKIN BIOPSY

When do I do it?

  • Sample any lesion(s) that look unusual or behaves in an unexpected manner
  • Consider a skin biopsy if the animal has failed to respond to an empirical course of therapy
  • Consider a skin biopsy if the animal is systemically ill
  • Biopsy any nodule or non-healing ulcer as these may be neoplastic
  • If the potential therapy is potentially dangerous or expensive a diagnosis should be confirmed with histopathology
  • To rule out other diagnoses

What can I find?

  • Confirm a clinical diagnosis
  • Rule out a suspected clinical diagnosis
TECHNIQUE IMAGES : SKIN BIOPSY
Disposable biopsy punch
Disposable biopsy punch
Skin biopsy equipment
Equipment needed for performing a skin biopsy
Biopsy punch being used
The punch is held at right angles to the skin and turned in 1 direction applying pressure
Removing sample
The sample is removed by gently grasping the base of the punch with a forceps, elevating it and then cutting. 

What do I need?

  • Skin punch biopsy (4 mm or 6 mm), thumb forceps, iris scissors, scalpel blade if performing a wedge biopsy, needle holder, suture material, 10% formalin

How do I do it?

  • Local anesthesia with sedation and pain management if needed
  • Skin is NOT prepped
  • If necessary, gently clip the overlying hair
  • 1-2% lidocaine or bupivacaine
  • Sodium bicarbonate to reduce stinging (1:9)
    0.1ml bicarbonate to 0.9ml lidocaine
  • Epinephrine 1:1,000 into hub of the syringe
    0.75–1cc per site, use 25 gauge needle
  • Recommended safe dose of 2% lidocaine
    Dogs:1–1.5 ml/ 4kg
    Cats: 0.5–0.75 ml/ 4kg
    Dilute 50:50 with saline if larger volume needed
  • Wait up to 10 minutes for the injection to take effect

Tip

  • Take several samples to increase the likelihood of selecting a diagnostic area
  • Request a complete microscopic description, not just a diagnosis, as this may help a dermatologist determine the cause of the problem
  • Send the samples to a pathologist with an interest in dermatology as they are more likely to be able to match the microscopic changes with a specific etiologic diagnosis
  • Provide the pathologist with a list of differential diagnoses and describe the signalment, clinical pattern and lesions seen, and past therapies

abscess

A discrete swelling containing purulent material, typically in the subcutis

Photo of abscess

Perianal abscess in a dog

alopecia

Absence of hair from areas where it is normally present; may be due to folliculitis, abnormal follicle cycling, or self-trauma

Photo of alopecia

Extensive alopecia secondary to cutaneous epitheliotropic lymphoma

alopecia (“moth-eaten”)

well-circumscribed, circular, patchy to coalescing alopecia, often associated with folliculitis

Photo of alopecia (“moth-eaten”)

“Moth-eaten” alopecia secondary to superficial bacterial folliculitis

angioedema

Regional subcutaneous edema

Photo of angioedema

Angioedema due to cutaneous drug eruption

annular

Ring-like arrangement of lesions

Photo of annular

Annular lesions in a dog with erythema multiforme

atrophy

Thinning of the skin or other tissues

Photo of atrophy

Cutaneous atrophy due to glucocorticoids

bulla

Fluid-filled elevation of epidermis, >1cm

Photo of bulla

Bullae in a dog with bullous pemphigoid

hemorrhagic bullae

Blood-filled elevation of epidermis, >1cm

Photo of hemorrhagic bullae

Interdigital hemorrhagic bulla in a dog with deep pyoderma and furunculosis

comedo

dilated hair follicle filled with keratin, sebum

Photo of comedo

Comedones on the ventral abdomen of a dog with hypercortisolism

crust

Dried exudate and keratinous debris on skin surface

Photo of crust

Multifocal crusts due to pemphigus foliaceus

cyst

Nodule that is epithelial-lined and contains fluid or solid material.

Photo of cyst

Epidermal inclusion cyst

depigmentation

Extensive loss of pigment

Photo of depigmentation

Depigmentation of planum nasale in dog with vitiligo.

ecchymoses

Patches due to hemorrhage >1cm

Photo of ecchymoses

Ecchymoses of a dog’s leg due to vasculitis

epidermal collarettes

Circular scale or crust with erythema, associated with folliculitis or ruptured pustules or vesicles

Photo of epidermal collarettes

Epidermal collarettes in a dog with Staphylococcus superficial bacterial folliculitis

erosion

Defect in epidermis that does not penetrate basement membrane. Histopathology may be needed to differentiate from ulcer.

Photo of erosion

Erosions in a dog with vasculitis

erythema

Red appearance of skin due to inflammation, capillary congestion

Photo of erythema

Erythema in a dog with cutaneous drug eruption

eschar

Thick crust often related to necrosis, trauma, or thermal/chemical burn

Photo of eschar

Eschar from physical trauma

excoriation

Erosions and/or ulcerations due to self-trauma

Photo of excoriation

Excoriations in a cat with atopic dermatitis

fissure

Excessive stratum corneum, confirmed via histopathology. This term is often used to describe the nasal planum and footpads.

Photo of fissure

Fissures of the footpads in a dog with superficial necrolytic dermatitis

fistula

Ulcer on skin surface that originates from and is contiguous with tracts extending into deeper, typically subcutaneous tissues

Photo of fistula

Perianal fistulas in a dog

follicular casts

Accumulation of scale adherent to hair shaft

Photo of follicular casts

Follicular casts surrounding hairs from a dog with hypothyroidism

hyperkeratosis

Excessive stratum corneum, confirmed via histopathology. This term is often used to describe the nasal planum and footpads.

Photo of hyperkeratosis

Idiopathic hyperkeratosis of the nasal planum (left) and footpads (right)

hyperpigmentation

Increased melanin in skin, often secondary to inflammation

Photo of hyperpigmentation

Inflammatory lesions (left) resulting in post-inflammatory hyperpigmentation (right)

hypopigmentation

Partial pigment loss

Photo of hypopigmentation

Idiopathic hypopigmentation of planum nasale

hypotrichosis

Lack of hair due to genetic factors or defects in embryogenesis.

Photo of hypotrichosis

Congenital hypotrichosis in chocolate Labrador puppies.

leukoderma

Lack of cutaneous pigment

Photo of leukoderma

Macular leukoderma in a dog

leukotrichia

Loss of hair pigment

Photo of leukotrichia

Progressive leukotrichia in patient with vitiligo.

lichenification

Thickening of the epidermis, often due to chronic inflammation resulting in exaggerated texture

Photo of lichenification

Lichenification of skin in a dog with chronic atopic dermatitis and Malassezia dermatitis

macule

Flat lesion associated with color change <1cm

Photo of macule

Pigmented macule (left) Erythematous macule (right)

melanosis

Increased melanin in skin, may be secondary to inflammation.

Photo of melanosis

Post inflammatory hyperpigmentation of this dog’s thigh

miliary

Multifocal, papular, crusting dermatitis; a descriptive term, not a diagnosis

Photo of miliary

Miliary dermatitis in a flea allergic cat

morbiliform

A erythematous, macular, papular rash; the erythematous macules are typically 2-10 mm in diameter with coalescence to form larger lesions in some areas

Photo of morbiliform

Morbiliform eruptions in a dog with a cutaneous drug reaction

nodule

A solid elevation >1cm

Photo of nodule

Nodules on nose of dog with cutaneous histiocytosis.

onychodystrophy

Abnormal nail morphology due to nail bed infection, inflammation, or trauma; may include: Onychogryphosis, Onychomadesis, Onychorrhexis, Onychoschizia

Photo of onychodystrophy

Onychodystrophy in dog with chronic allergies

onychogryphosis

Abnormal claw curvature; secondary to nail bed inflammation or trauma

Photo of onychogryphosis

Onychogryphosis in a dog with symmetric lupoid onychodystrophy

onychomadesis

Claw sloughing due to nail bed inflammation or trauma

Photo of onychomadesis

Onychomadesis in a dog with symmetric lupoid onychodystrophy

onychorrhexis

Claw fragmentation due to nail bed inflammation or trauma

Photo of onychorrhexis

Onychorrhexis in a dog with symmetric lupoid onychodystrophy

onychoschizia

Claw splitting due to nail bed inflammation or trauma

Photo of onychoschizia

Onychoschizia in a dog with symmetric lupoid onychodystrophy

papule

Solid elevation in skin ≤1cm

Photo of papule

Papules on a dog with superficial bacterial folliculitis

papules

Solid elevation in skin ≤1cm

Photo of papules

Papules on a dog with superficial bacterial folliculitis

paronychia

Inflammation of the nail fold

Photo of paronychia

Paronychia in a dog with symmetric lupoid onychodystrophy

patch

Flat lesion associated with color change >1cm

Photo of patch

Hypopigmented patch (left), erythematous patch (right)

petechiae

Small erythematous or violaceous lesions due to dermal bleeding

Photo of petechiae

Petechiae in a dog with cutaneous vasculitis

phlebectasia

Venous dilation; most commonly associated with hypercortisolism

Photo of phlebectasia

Phlebectasia and cutaneous atrophy due to hypercortisolism in a dog

plaques

Flat-topped elevation >1cm formed of coalescing papules or dermal infiltration

Photo of plaques

Plaques in a cat with cutaneous lymphoma

pustule

Raised epidermal infiltration of pus

Photo of pustule

Pustules on the abdomen of a dog with superficial staphylococcal pyoderma.

reticulated

Net-like arrangement of lesions

Photo of reticulated

Reticulated leukotrichia on the back of a horse

scale

Accumulation of loose fragments of stratum corneum

Photo of scale

Loose, large scales due to ichthyosis in a Golden Retriever

scar

Fibrous tissue replacing damaged cutaneous and/or subcutaneous tissues

Photo of scar

Scarring (right) following the healing of an ulcer (left) in a dog with sterile nodular dermatitis

serpiginous

Undulating, serpentine (snake-like) arrangement of lesions

Photo of serpiginous

Serpiginous urticarial lesions on a horse

telangiectasia

Permanent enlargement of vessels resulting in a red or violet lesion (rare)

Photo of telangiectasia

Telangiectasia in a dog with angiomatosis

ulcer

A defect in epidermis that penetrates the basement membrane. Histopathology may be needed to differentiate from an erosion.

Photo of ulcer

Ulcerations of the skin of a dog with vasculitis.

urticaria

Wheals (steep-walled, circumscribed elevation in the skin due to edema ) due to hypersensitivity reaction

Photo of urticaria

Urticaria in a horse

vesicle

Fluid-filled elevation of epidermis, <1cm

Photo of vesicle

Vesicles and bullae on ear pinna due to bullous pemphigoid

wheal

Steep-walled, circumscribed elevation in the skin due to edema

Photo of wheal

Wheals associated with intradermal allergy testing in a horse