Dermatopathology

Question 1

What are primary skin lesions?

Answer 1

Develop as a direct result of the disease process

Question 2

What are secondary skin lesions?

Answer 2

Evolve from primary lesions or develop as a consequence of the patient’s activities

Question 3

What are some examples of primary skin lesions?

Answer 3

Macule, patch, wheal, papule, nodule, tumour, vesicle, bulla, pustule, comedo, follicular cast, alopecia, scale and crusts

Question 4

What are some examples of secondary skin lesions?

Answer 4

Epidermal collarette, scar, excoriation, erosion, ulcer, fissure, lichenification, hyperpigmentation and callus

Question 5

What needs to be noted as well as the type of lesion present?

Answer 5

The configuration of the lesion

Question 6

In what diseases are single lesions more common?

Answer 6

Dermatophytosis or cutaneous neoplasia

Question 7

What do linear lesions tend to indicate?

Answer 7

External trauma or lesions associated with a blood vessel, dermatome or congenital malformation

Question 8

What is associated with annular lesions?

Answer 8

Peripheral spreading of disease such as in pyoderma or dermatophytosis

Question 9

What do symmetrical skin lesions typically show?

Answer 9

Systemically-mediated disease

Question 10

What approach is used in histological interpretation of skin biopsies?

Answer 10

Pattern analysis approach of how the inflammatory cells are distributed in the skin

Question 11

What are the different methods of taking a skin biopsy?

Answer 11

Disposable biopsy punches (6mm/8mm) and close defect with 1 or 2 sutures
Excisional biopsies especially if large lesions or bullae present

Question 12

How would you take a skin biopsy?

Answer 12

In quiet animals can be done just under 2% lignocaine (local anaesthetic) but sedation is advised in more fractious animals
If taking excisional biopsies perform under general anaesthetic

Question 13

What lesions should be biopsied?

Answer 13

Intact primary lesions and don’t include a margin of unaffected skin although in ulcerative diseases elliptical excisions across the lesion margins are valuable

Question 14

What does a perivascular inflammatory pattern look like histologically?

Answer 14

Inflammatory cells around the dermal blood vessels and can be classed as superficial, mid or deep

Question 15

What do different inflammatory cells present indicate in terms of disease process?

Answer 15

Neutrophils = self-trauma or pyoderma
Eosinophils = ectoparasites or hypersensitvity
Mononuclear cells = chronic dermatitis or immunologic causes

Question 16

What does an interstitial pattern look like histologically?

Answer 16

Spreading out of inflammatory cells from the original perivascular pattern

Question 17

What is the histological appearance of an interface inflammatory process? What does it indicate?

Answer 17

Dermo-epidermal junction is obscured by an accumulation of inflammatory cells
Auto-immune disease targeting epidermis/drug reaction

Question 18

What else might be seen with an interface inflammatory process?

Answer 18

Loss of pigment or vesicles/bullae and erosions/ulcers

Question 19

What is does a nodular inflammatory pattern look like histologically? What disease is it commonly seen in?

Answer 19

Dense clusters of inflammatory cells

Granulomatous dermatitis

Question 20

What causes vesicles and bullae (blisters)?

Answer 20

Death of clusters of epidermal cells or from loss of adhesion between cells and there is an accumulation of fluid exudate in the defect

Question 21

How do pustules differ from vesicles and bullae?

Answer 21

Inflammatory cells predominate rather than fluid

Question 22

What diseases commonly cause vesicles and pustules?

Answer 22

Vesicles are commonly caused by viral infections such as foot and mouth
Pustules are caused by bacterial infections

Question 23

What does acantholysis refer to? How does it occur? Why is it important?

Answer 23

Destruction of desmosomal attachments between keratinocytes
Can be enzymatic or as a result of auto-immune attack
Presence or absence is an important part of assessing intra-epidermal vesicular or pustular dermatitis

Question 24

What defects are see with intra-epidermal vesicular or pustular dermatitis?

Answer 24

Pustules and vesicles or bullae

Question 25

What is the histological appearance of sub-epidermal vesicular dermatitis?

Answer 25

Epidermis is separating from the underlying dermis

Question 26

What can cause sup-epidermal vesicular dermatitis?

Answer 26

Structural protein defects in newborn animals

Acquired disease reflecting auto-immune attack on structural proteins

Question 27

What does folliculitis look like histologically?

Answer 27

Inflammation of the hair follicle with inflammatory cells surrounding the hair follicle

Question 28

What is folliuculitis often preceded or accompanied by? What other pattern can it occur as part of?

Answer 28

Perifolliculitis

Perivascular pattern

Question 29

What is furunulosis? What is the result of furunculosis in the dermis?

Answer 29

Inflammatory destruction of the hair follicle with rupture and extrusion of follicle contents into the dermis. Foreign body response is set up and may progress to scarring or fistula formation or panniculitis

Question 30

What is an atrophic pattern? What is the most commonly affected layer? What is it often a result of?

Answer 30

Not inflammatory but characterised by reductions in the size of different components of the skin
Most commonly epidermal thinning with small telogen-phase follicles
Endocrine disease