Skin Biopsy Guidelines

Question 1

describe site selection for biopsy

Answer 1

the goal is to collect primary lesions!!

1. nodules: directly into nodules/bumps (incisional)
   -elliptical wedge biopsies are best suited for solitary nodules that can be entirely excised and deep nodular lesions in the panniculus (usually poorly accessed with punches)

Question 2

describe erosions versus ulcers

Answer 2

erosions: shallow epidermal defect that does not penetrate basal membrane

ulcers: break in continuity of epidermis and basement membrane

clinical signs accompanying erosions and ulcers that are consistent with autoimmune blistering skin disease:
-mucosal or mucocutaneous lesions
-bilaterally symmetrical distribution, especially on the face

-enhance yield in this case via 5 rules:
1. never biopsy an entirely ulcerated area
2. select a new lesion, which may be proximal to an ulcerated area
3. prefer a wedge biopsy across the margin of normal and ulcerated skin
4. take multiple biopsies from representative areas of various stages
5. biopsy before instituting glucocorticoid therapy

Question 3

how to sample erosions/ulcers on the nasal planum?

Answer 3

at the margin of lesional to non-lesional skin

take multiple biopsies from representative areas of various stages

Question 4

describe how to sample with alopecia

Answer 4

if it is the primary lesion (cushing’s or vaccine-induced vasculitis), collect multiple skin biopsies:

1. the central (most alopecic area)
2. marginal to healthy
3. healthy

Question 5

describe getting samples ready for submission

Answer 5

1. 10% buffered formalin is standard
2. BUT before you dunk:
   -consider if you want to do cytology, if you need to ink margins because you want tumor margins, if you need fresh tissue for culture, PCR, etc.
3. for really small pieces: put in a cassette, but do NOT crush in the lid and LABEL!!!!
   -if come with sponges, remove the sponges because could make you crush the tissue in the lid
4. if you think you have a neoplasm and want margins, INK them and use sutures for orientation before you submit
5. fresh tissues for culture and PCR:
   -place each tissue in separate tube with enough sterile saline (not bacteriostatic) to keep moist
   -if you use a whirl-pack bag wrap tissue in sterile moistened gauze
   -fresh tissue usually better than swab
6. jars:
   -everybody in a separate container unless in labeled cassette

Question 6

describe filling out the submission form

Answer 6

1. signalment
2. location, clinical signs, distribution of lesions
3. treatment history:
   -usually discontinue oral corticosteroids and immunomodulatory therapies prior to biopsy but if you haven’t SAY SO
4. other diagnostics: skin scraping, clin path findings, cultures, etc.
5. response to treatment
6. additional pertinent information
7. any differentials to rule in/rule out

Question 7

what happens to samples submitted to a lab?

Answer 7

takes about 24 hours to generate a slide for evaluation once submit

1. embedded in parafin wax
2. stained with hematoxylin and eosin
3. +/- special stains: based on the look of the etiologic agents, the specific cell types, the type of pigment, and presence of fibrosis, amyloid, or fibrin
4. +/- immunohistochemistry: for
   -etiologic agent determination
   -tumor type determination
   -prognostication

Question 8

describe how to interpret the biopsy report

Answer 8

1. gross:
   -what was submitted, what it looked like, and how trimmed
2. histopathology:
   -a detailed description of what the pathologist sees
3. diagnoses:
   -morphologic: severe, chronic, focal, pyogranulomatous dermatitis with hyphae (example)
   -etiologic: pythium dermatitis
   -disease or condition: cutaneous pythiosis
4. comment: read CAREFULLY
   -interpretation of findings
   -may include a ddx
   -may rule in/out some of your ddx
   -may request to do additional testing: IHC for infectious agent or tumor type, PCR from scrolls
   -may suggest you refer
   -express the need for a second opinion