Dermatopathology Flashcards
What are primary skin lesions?
Develop as a direct result of the disease process
What are secondary skin lesions?
Evolve from primary lesions or develop as a consequence of the patient’s activities
What are some examples of primary skin lesions?
Macule, patch, wheal, papule, nodule, tumour, vesicle, bulla, pustule, comedo, follicular cast, alopecia, scale and crusts
What are some examples of secondary skin lesions?
Epidermal collarette, scar, excoriation, erosion, ulcer, fissure, lichenification, hyperpigmentation and callus
What needs to be noted as well as the type of lesion present?
The configuration of the lesion
In what diseases are single lesions more common?
Dermatophytosis or cutaneous neoplasia
What do linear lesions tend to indicate?
External trauma or lesions associated with a blood vessel, dermatome or congenital malformation
What is associated with annular lesions?
Peripheral spreading of disease such as in pyoderma or dermatophytosis
What do symmetrical skin lesions typically show?
Systemically-mediated disease
What approach is used in histological interpretation of skin biopsies?
Pattern analysis approach of how the inflammatory cells are distributed in the skin
What are the different methods of taking a skin biopsy?
Disposable biopsy punches (6mm/8mm) and close defect with 1 or 2 sutures
Excisional biopsies especially if large lesions or bullae present
How would you take a skin biopsy?
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
What lesions should be biopsied?
Intact primary lesions and don’t include a margin of unaffected skin although in ulcerative diseases elliptical excisions across the lesion margins are valuable
What does a perivascular inflammatory pattern look like histologically?
Inflammatory cells around the dermal blood vessels and can be classed as superficial, mid or deep
What do different inflammatory cells present indicate in terms of disease process?
Neutrophils = self-trauma or pyoderma
Eosinophils = ectoparasites or hypersensitvity
Mononuclear cells = chronic dermatitis or immunologic causes
What does an interstitial pattern look like histologically?
Spreading out of inflammatory cells from the original perivascular pattern
What is the histological appearance of an interface inflammatory process? What does it indicate?
Dermo-epidermal junction is obscured by an accumulation of inflammatory cells
Auto-immune disease targeting epidermis/drug reaction
What else might be seen with an interface inflammatory process?
Loss of pigment or vesicles/bullae and erosions/ulcers
What is does a nodular inflammatory pattern look like histologically? What disease is it commonly seen in?
Dense clusters of inflammatory cells
Granulomatous dermatitis
What causes vesicles and bullae (blisters)?
Death of clusters of epidermal cells or from loss of adhesion between cells and there is an accumulation of fluid exudate in the defect
How do pustules differ from vesicles and bullae?
Inflammatory cells predominate rather than fluid
What diseases commonly cause vesicles and pustules?
Vesicles are commonly caused by viral infections such as foot and mouth
Pustules are caused by bacterial infections
What does acantholysis refer to? How does it occur? Why is it important?
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
What defects are see with intra-epidermal vesicular or pustular dermatitis?
Pustules and vesicles or bullae
