dermpath - skin biopsies

Question 1

when do we take a skin biopsy?

Answer 1

◼ Skin biopsies are taken for non ‘mass’ skin disease.
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Non mass skin disease
◼ Inflammatory skin diseases
◼ Noninflammatory skin diseases

Question 2

Diagnosis in Clinical Derm - 9 steps

Answer 2

1. Signalment
2. History (pruritic or not; treatments and response)
3. Differential diagnosis
4. Examination of skin
5. Tentative diagnosis
6. Diagnostic (Laboratory) tests – Biopsy is a test
7. Match with signalment and history
8. Final diagnosis
9. Response to therapy
   ALWAYS PERFORM dermatologic clinical examination including cytology.

Question 3

Laboratory tests in Clin Derm

Answer 3

◼ Parasitological examination / response trial
◼ Cytology
> Skin scraping
> Hair plucking
> Coat brushing
> Acetate tape preparation
> FNA
◼ Culture and sensitivity
◼ Biopsy -DERMPATH
ALWAYS perform dermatological examination

Question 5

1. Biopsy appropriate cases - what are they?

Answer 5

◼ Biopsy is part (not start!) of clinical workup
◼ Exclude diseases clinically
> Skin scraping and tape strip cytology
> Trichogram
> Culture
> Ectoparasites
> Fungi – Malassezia
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ALWAYS perform dermatological examination

Question 6

Biopsy -
Indications as per
Canadian Academy of Vet Dermatology

Answer 6

◼ Nodular skin lesions
◼ Suspect epitheliotropic lymphoma
◼ Failure to respond to therapies
◼ Suspect autoimmune disease
◼ Persistent alopecia of unknown cause
◼ Suspected disease that is long, expensive or life threatening
◼ Follicular casts
◼ Rapidly progressive systemically ill pet
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Important: you do NOT biopsy pruritic skin disease as a first line. You only do so when everything fails.

Question 7

how many biopsies should we take?

Answer 7

Take MULTIPLE biopsies from a range of lesions
6 is good > 1 for bacterial culture, 5 for histopathology
(3 is minimum… but foster not a fan of this)

Question 8

biopsy - what is an “excellent submission”

Answer 8

6 samples, each 6 mm
> Take MULTIPLE biopsies from a range of lesions……place in separate containers or mark for identification

Question 9

Biopsy trimming, marking

Answer 9

◼ Biopsies are trimmed in the direction of the hair.
◼ Mark direction with permanent marker

Question 10

To get the BEST results from skin biopsies…….
- prep
- technique
- instrument

Answer 10

◼ Don’t surgically prepare the biopsy site!!
◼ This is very important if there are scales, crusts, vesicles, or pustules
◼ Include scale (keratin) and crust (exudate)
◼ Be gentle!! Don’t crush, squeeze, dehydrate the biopsy
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Choose the right biopsy instrument
◼ Baker skin biopsy punch
> 6mm preferable for most situations
> 3mm for delicate sites
Wedge or excisional biopsies for large lesions/nodules

Question 11

Biopsy - Periphery vs center of lesion??

Answer 11

◼ Need to be where the action is…
◼ No fixed rule, common sense, clinical acumen
◼ Separate biopsies, if different areas need to be identified

Question 12

Clinical signs and location for biopsy
◼ Pruritic
◼ Scaling
◼ Crusting
◼ Nodular
◼ Ulcerative
◼ Alopecia

Answer 12

◼ Pruritic – range of affected areas
◼ Scaling – range of affected areas
◼ Crusting – pustules, vesicles, new lesions, crusts
◼ Nodular – excisional or wedge biopsies
◼ Ulcerative – edge of lesion, vesicles
◼ Alopecia – severe and less severely affected

Question 13

Good candidates for BIOPSY…….

Answer 13

◼ Clinical work-up unsuccessful…
◼ Clinical features of immune-mediated disease or other diseases where biopsy confirmation is necessary
◼ No response to apparently appropriate therapy…
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Anything really unusual…….Or really serious
- eg. hyphomycosis, pustular demodicosis

Question 14

biopsy for chronically itchy dogs - how helpful?

Answer 14

◼ LOW expectation for a definitive diagnosis
◼ Know why you are doing the biopsy – ie rule out some diagnoses
◼ Pathology report will have a long comment on work-up of a pruritic animal!!!

Question 15

what we need to include with biopsy
- What the dermatopathologist need to know

Answer 15

1. Full signalment
2. History
3. Description of lesions
4. Treatments tried and result
5. Your differential diagnoses

Question 16

what is considered full signalment information, to tell the dermatopathologist?

Answer 16

◼ Breed
> Many dermatoses are breed-associated
> ‘Mixed breed’ is NOT helpful > rather put down phenotype
> Most texts list breed susceptibilities to skin diseases
◼ Age
> Juvenile cellulitis usually seen in puppies
> Canine atopic dermatitis rarely develops in puppies or aged dogs
◼ Sex
> Sex hormone responsive
> Male feminization
> M, Mn, F, Fs – which is it? If you neuter/spay the animal and take biopsies, it is not Mn or Fs

Question 17

what part of history should be included with a skin biopsy?

Answer 17

◼ Duration of problem(s)
◼ Major clinical problem(s) identified
◼ Previous work-up, results and response
◼ Results of recent cytology, skin scrapings, fungal or bacterial cultures, other clinical pathology etc

Question 18

what information / description of lesions should we include with a biopsy?

Answer 18

◼ use a diagram for location of lesions
> Distribution, distribution, distribution
◼ presence or absence of pruritus and pruritus scale
◼ Crust is not Scale
◼ describe lesions using correct terminology
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◼Send pictures!

Question 19

we should tell the dermatopathologist information about treatments tried and result, especially…

Answer 19

◼ Antibiotics (dose and duration)
◼ Treatment for parasites (dose, number of therapies)
◼ Corticosteroid therapy (dose, duration, most recent treatment)
Always perform ‘dermatology clinical examination’

Question 20

should we include Ddx with biopsy?

Answer 20

◼ Must know diseases you are genuinely considering, preferably ranked
◼ Best to confirm a diagnosis or exclude diagnosis
◼ Not helpful to list every possibility

Question 21

Dermatopathology report - what is included

Answer 21

◼ The 3 parts of a pathology report are
> Description of microscopic lesions
> Diagnosis
> Comment
◼ Read Dermatopathology references
◼ Telephone if discrepancy between clinical signs and diagnosis
** Use a Dermatopathologist**