dermatological diagnostics

Question 1

how many samples do you take for a skin biopsy

Answer 1

sample a representative range of lesions
- take multiple samples (min 3 unless solitary lesion)
- sample fully developed primary lesions where possible, avoiding traumatised skin/necrotic crust

Question 2

what are the best sites to take skin biopsy for alopecia

Answer 2

• across the margin of the alopecic area AND
• the area of maximum hair loss
• normal haired skin wedge biopsy across margin of alopecic area often more useful than punch

Question 3

what is the best site to take a skin biopsy for ulcerated skin

Answer 3

skin adjacent to the ulcer where the epidermis is still intact

Question 4

what is the best site to take a biopsy for pustules, vesicles or bulla

Answer 4

• remove whole lesion without disruption
• often very delicate
• difficult with a punch not to cause damage
• consider wedge biopsy

Question 5

how do you prepare the sample site for biopsy

Answer 5

• avoid disrupting skin surface
• clip hair but not too short, scissor preferred to clippers
• do not disturb crusts or skin surface
• no not prep or scrub the skin unless excisional biopsy of nodules

Question 6

how do you mark a site for skin biopsy

Answer 6

• draw circle around lesion in indelible marker
• infiltrate local anaesthetic into subcutis around periphery of circle
• care not to exceed max volume of local for weight
• check efficacy of analgesia by pricking with a needle

Question 7

what is a punch biopsy

Answer 7

• quick and convenient
• use 6mm or 8mm biopsy punches routinely, 3/4mm only for delicate structures
• hold perpendicular to skin surface
• rotate in one direction, not back and forth
• no not reuse

Question 8

what is a wedge biopsy

Answer 8

• excision with scalpel

Question 9

how do you handle the biopsy once taken

Answer 9

• care not to destroy sample
• handle gently by subcutaneous tissue only (never by dermis or epidermis)
• use fine instruments or needle

Question 10

how do you prep a biopsy sample for histopath

Answer 10

• blot blood gently from underside of sample
• place promptly into 10% formalin minimum 10x the volume of the tissue sample
• if thin sample, place on a stiff card or end of woode tongue depressor subq tissue down to prevent curling, then place whole unit in formalin
• separate normal, marginal and central lesions in different pots
• give pathologist brief hx, suspected ddx

Question 11

how do you prepare a biopsy sample for prep of bacterian and fungal tissue culture

Answer 11

• withdraw antibiotics for 5-7 days, topical antimicrobials 3+ days priror to sampling for bacterial culture
• gently blot surface with alcohol swab to remove contamination and allow to dry
• submit small punch tissue biopsy in sterile glass tube +/- spot of sterile saline
• avoid contamination with formalin as kills organisms
• if necessary, can go in fridge or freezer

Question 12

what does perivascular dermatitis look like

Answer 12

Question 13

what does interface dermatitis look like on histopath

Answer 13

Question 14

what does vasculitis look like histopathologically

Answer 14

Question 15

what does nodular/diffuse dermatitis look like histopath

Answer 15

Question 16

what does intradermal vesicular/pustular dermatitis look like on histo

Answer 16

Question 17

what does subepidermal vesicular/pustular dermatitis look like on histo

Answer 17

Question 18

what does panniculitis look like on histopath

Answer 18

Question 19

what does atopic dermatosis look like on histopath

Answer 19

Question 20

What is an acanthocyte?

Answer 20

Epidermal cell free in a vesicle/pustule, caused by acantholysis.

Question 21

What is acantholysis?

Answer 21

Loss of cohesion between cells of the living epidermis.

Question 22

What is acanthosis?

Answer 22

Hyperplasia of stratum spinosum.

Question 23

What is apoptosis?

Answer 23

Individual cell death, requiring energy.

Question 24

What is dyskeratosis?

Answer 24

Abnormal, premature or imperfect keratinisation of keratinocytes.

Question 25

What is epidermolysis?

Answer 25

Degeneration of epidermal basal layer → separation of epidermis from dermis.

Question 26

What is exocytosis (in dermatopathology)?

Answer 26

Migration of inflammatory cells from dermis → epidermis.

Question 27

What is hydropic degeneration?

Answer 27

Vacuoles in stratum basale → intrabasal or subepidermal clefts.

Question 28

What is hyperkeratosis?

Answer 28

Increase in stratum corneum (orthokeratotic/parakeratotic; basket-weave/compact).

Question 29

What is intracellular oedema?

Answer 29

Occurs with hydropic degeneration of basal cells and ballooning degeneration (seen with herpes virus infections).

Question 30

What is necrolysis?

Answer 30

Epidermal necrosis with no dermal involvement and minimal inflammation.

Question 31

What is orthokeratosis?

Answer 31

Excessive cornification – keratinocytes lose nuclei.

Question 32

What is parakeratosis?

Answer 32

Excessive cornification – keratinocytes retain

Question 33

What is pigment incontinence?

Answer 33

Release of melanin granules into superficial dermis.

Question 34

What is spongiosis?

Answer 34

Intercellular oedema in the epidermis.