Dermatopathology Flashcards
Acantholysis
Loss of keratin cohesiveness

Acanthosis
Increased thickness of stratum spinosum

Alopecia
Hair loss/ failure to grow
Atopy
Allergic skin disease
Ballooning degeneration
Intracellular oedema

Bullae
Collection of fluid > 1cm in diameter

Folliculitis
Luminal, mural or perifollicular inflammation of the hair follicle

Furunculosis
Luminal, mural or perifollicular inflammation secondary to rupture of the follicular wall (keratin = non-self)

Dermal pyogranulomatous inflammation
Furunculosis
Hyperkeratosis
Increased keratin thickness (may be para/ orthrokeratotic nuclei)

Parakeratotic
Nuclei seen
Orthokeratotic
No nuclei seen
Pustule
Cavitation of epidermis filled with inflammatory cells

Pigmentary incontinence
Melanin/ melanophages within the dermis

Seborrhoea
Increased scale with or without greasiness

Seborrhoea olesa
Increased scale with increased greasiness
Seborrhoea sicca
Increased scale without greasiness
Spongiosis
Epidermal intercellular oedema

Vesicle
Fluid filled blister

Name three aetiological agent which cause vasculitis
Rickettsia
Autoimmunity - immune complexes
Erysipelothrix - septic emboli
Purpura
Purple-red rash of the skin
Vasculitis is characterised by what gross changes?
Erythema
Plaques
Macules
Purpura
Ulceration
Dermal atrophy with chronicity
Describe this lesion

The skin of this pig shows multifocal to coelescing ‘diamond-shaped’ erythrematous red lesions. They range in size from 3x3 cm to 1x1cm. They are dark red at the periphery but often have a pale centre.
Acute severe multifocal-coelescing erythrematous vasculitis
Diamond disease - Erysipelothrix
What pathological change is seen on this histological slide?

Adnexal atrophy - fading follicles, characteristic of chronic vasculitis
What type of vasculitis is characterised in this image?
What aetiology would be expected?

Neutrophilic
Due to type 3 hypersensitivity or septicaemia
What type of vasculitis is characterised in this image?
What aetiology would be expected?

Lymphoplasmacytic
Cell-mediated
What type of vasculitis is characterised in this image?
What aetiology would be expected?

Eosinophilic
Type 1 hypersensitivity
What histological changes would be expected with vasculitis?
Karyorrhectic cell debris
Fibrinoid necrosis + fibrin/ haemorrhage
Faded follicles with chronicity
Describe the lesion.

Multifocal to coelescing redenning of the skin. Round lesions show flaking scale at the edges and range from 1x1cm to 3x3cm. Erythrematous papules.
Histologically: subcorneal pustules and n# infiltration
Acute moderate to severe multifocal to coelescing haemorrhagic dermatitis
Aetiology: Pemphigus foliaceus
Describe this lesion

The skin of this piglet shows extensive focal erythema. Large grey to brown crusts are present. Approximately 20% of the skin of the face is affected.
Acute severe focally extensive bacterial dermatitis.
Aetiology: Staphylococcus hyicus exotoxin (MMP)
Describe the lesion

Subcorneal pustular dermatitis
Epidermis covered with ortho- and parakeratotic hyperkeratosis
Neutrophils and bacterial colonies
Aetiology: Staphylococcus hyicus
Which pathogen is shown here?

Dermatophilus congolensis
Thick, parakeratotic crusts found on the head, back and hindquarters (ie persistently soaked) areas of a horse would be indicative of what pathogen?
Dermatophilus congolensis
Which species of bacteria are implicated in deep pyoderma?
Staphylococcus
Streptococcus
Corynebacterium
Pseudomonas
How would deep pyoderma lesions progress with increased pathology?
- Follicular papules
- Pustule
- Crust formation and coalescing ulcers and alopecia
- Dark red nodules, ulcers and fistulae
- Lymphadenopathy and fever
- Epidermal acanthosis
Abscess
Focal non-specific severe suppurative inflammation of the deep dermis and panniculum
Describe the histological appearance of an abscess.
Central core of neutrophilic debris and necrotic material surrounded by granulation tissue.
Well demarcated
Describe the histological appearance of cellulitis.
Poorly demarcated
Extensive suppurative/ pyogranulomatous inflammation
Oedema
Haemorrhage
Thrombosis
What histological changes are seen here?

“Sulphur granules” -
masses of basophilic to amphophilic organisms bordered by bright eosinophilic Splendore-Hoeppli material
Caused by Actinomyces/ Nocardia
Panniculitis
Inflammation of adipose tissue
Epitheliotrophic viruses.
Name four.
What histological changes are seen?
Pox viruses
- Capri - sheep pox
- Parapox - orf
- Orthopox - cowpox
- Suipox - swine pox
Histo: Cytoplasmic inclusion bodies
Describe the lesion

Multifocal-coelescing crusting lesions. Peripheral erythema of lesions. Papules and pustules. Ulceration of lesions is seen.
Intracytoplasmic inclusion bodies on histology
Cowpox - particularly in immunosupressive lesions
Multifocal-coelescing raised to flat-grey crusts seen at the lip commissure of a lamb.
What aetiology would be expected?
Orf - parapox virus
Contagious pustular dermatitis
Orf
Multifocal to coelescing nodular oval masses over the ear pinnae.
Suggest an aetiological agent.

Swinpox
Aetiology of dermatophytosis
Microsporium
Trichophyton
Epidermophyton
Which of these statements is incorrect?
- In impetigo (superficial pyoderma) the prototype lesion is a neutrophilic pustule
- “Greasy pig” disease is caused by a poxvirus
- Herpes virus and poxvirus can cause a dermatopathological disease in cats
- In deep pyoderma the initial lesion is a suppurative folliculitis
- Orf virus is causing proliferative lesions at the lip commissures
2
What species of Malassezia is usually implicated in malassezia dermatitis?
Pachydermatis (commensal)
Which of these two species of fungi cause pruritic skin disease?
Malassezia or Trichophyton
Malassezia
Describe this lesion

Chest and legs of the dog are focally extensively affected. There is severe lichenification of the skin with multifocal areas of erthema. The affected area shows severe alopecia and hyperpigmentation.
Chronic focally extensive severe dermatitis
Malassezia

Peanut shaped malassezia fungi
What histological changes are present in Malassezia dermatitis?
- Parakeratotic hyperkeratosis, epidermal hyperplasia with spongiosis. Mixed cell exocytosis occurs
- Yeasts aggregate within crusts or the stratum corneum

Which species cause dermatophytosis?
Microsporium
Trichophyton
Epidermophyton
Transmission of dermatophytosis.
Infected hair/ keratin fragments
Describe this lesion

Multifocal to coelescing, raised, alopecic areas of skin. The peripheral area of each round lesion (2x2cm) shows mild crusting. Lesions apear firm to touch.
Chronic MF-C moderate granulomatous dermatitis
Dermatophytosis

Fungal hyphae surround the hair follicle.
Dermatophytosis
Kerion
Mycotic pyogranuloma
Mycetoma
Which species is commonly involved?
Tumour-like lesion caused by fungi (due to wound contamination)
Actinomyces spp.

Fungal hyphae surrounded by lymphocytes and plasma cells.
Extensive fibrosis
Eumycotic mycetoma - Actinomyces
Pythiosis and lagenidiosis is caused by what fungal species present in stagnant water?
Pythium insidiosum and Lagenidium

Necrotic debris surrounded by inflammatory cells - eosinophils and epithelioid macrophages
Chronic focal severe eosinophilic necrotising dermatitis
Pythiosis and Lagenidiosis
Describe this lesion

Focal raised ulcerated nodule (4x4cm)
Exposed subcut tissue is reddened and haemorrhagic fluid oozes from a deep tract.
Chronic focal severe haemorrhagic dermatitis
Pythiosis
Describe the two aspects of Zygomycosis.
- Mucorales (angioinvasion and dissemination)
- Entomophthorales (local subcutaneous granulomas)
Outline the lifecycle of Benoitosis protozoa and describe the lesions they cause.
- Lifecycle - 2 host cycle - cat is definitive host
- Lesions - Intracellular cyst

Describe the immune response and therefore lesions caused by infections of Leishmaniasis.
- TH1 - alopecic
- TH2 - nodular

Amastigotes found within macrophages in blood sample - Leishmaniasis
Which parasitic species are associated with Myiasis?
- Cuterebra spp.: rabbit, rodents and, aberrantly, cats
- Hypoderma bovis and H. Lineatum : cattle (warble)
- Blowflies (lucilia, calliphora, etc): sheep

Folliculitis, keratolysis, degenerative neutrophils
Chronic focal moderate suppurative necrotising dermatitis/ folliculitis
Demodecosis
Bruise
Locat subcut/ intradermal haemorrhage
Progression leads erythrophagocytosis and degradation of haem pigment and therefore the colour change
Describe this lesion

MF-C
Oedematous, firm plaques
Well demarcated
Urticaria - Type 1 hypersensitivity
Atopic dermatitis
Cause
IgE hypersecretion
Excoriation
Self-trauma related abrasion

Eosinophil infiltration of skin - autoimmune reaction
Insect hypersensitivity is what type of reaction
T1/ T4 hypersensitivity caused by insect saliva, venom etc
Name the three aspects of the pemphigus autoimmunity complex
Condition, autoimmunity against..
- Pemphigous folliaceous - desmoglein1
- Pemphigous vulgaris - desmoglein 3
- Bullous pemphigoid - BPAG1/2
Pemphigus complex

Pemphigus foliaceus
Superficial epidermis affected
Pemphigus complex

Pemphigus vulgaris
Detachment at mucocutaneous junction
Pemphigus complex

Bullous pemphigoid
Cutaneous and mucosal detachment
What is the difference between Discoid and Systemic Lupus Erythematosus
Systemic -Involvement of multiple organs +/- skin lesions
Discoid - Localized cutaneous form
Photosensitive dermatitis restricted to the nasal planum is indicative of what autoimmune condition?
Discoid lupus erythematosus
Describe erythema multiforme
- Type III and IV hypersensitivity reactions -deposition of immune-complexes in vasculature and basal membrane
- Two forms:
Minor - symmetrical bilateral erythematous papules and macules. Classical “target” lesions
Major - widespread mucosal lesions, extensive necrotising and vesiculobullous skin lesions and systemic illness
•Histo: Characteristic interface dermatitis with necrotic keratinocytes and satellitosis. Epidermal necrosis

Describe alopecia areata
Bulbal inflammation and fragmentation of hairs
Histo: Peribulbar lymphocytic folliculitis - pigmentary incontinence - chronic lesions: telogen and atrophic follicles. Active inflammatory changes are difficult to observe
Deficiencies in vitamin a cause what clinical presentation?
Squamous epithelial hyperkeratosis (follicular keratosis)
Deficiency in vitamin e cause what clinical presentation?
Panniculitis due to steatonecrosis (lack of antioxidant protection)
Deficiency in vitamin b causes what clinical presentation
Dry seborrhoea with alopecia
You are presented with a pig with bilateral and symmetrical papules, erythema and crusts.
Discuss
Zinc deficiency
Histo - acathosis, epithelial hyperkeratosis (parakeratotic)
Superficial necrolytic dermatitis is characteristed by “french flag” histology.
What pathological changes lead to this?

- Parakeratotic hyperkeratosis (red),
- Spongiosis and oedematous spinous layer (white)
- Basal layer hyperplasia (blue)
Unknown aetiology but associated with hormonal imbalances.
Grossly appears as erosions and erythema
You are presented with a dog with symptoms as follows:
Bilateral and symmetrical hypotrichosis and alopecia of trunk, abdomen. Skin is diffusely thinned and less elastic. Hyperpigmentation, comedones and calcinosis cutis are also observed.
What would you suspect to find on histology?
Possible diagnosis?
Diffuse cutaneous atrophy with orthokeratotic hyperkeratosis and follicular keratosis

Describe the difference between eosinophilic lesions in cats.
- Eosinophilic plaque:
- Highly pruritic
- Inguinal, axillary and lateral thigh areas
- Eosinophilic granuloma:
- Raised, pink variably pruritic nodular lesions
- Haired skin (linear) and oral mucosa (nodular)
- •Indolent ulcer:
- Ulcerated plaque-like lesion on the upper lip
- Non pruritic and non painful
Describe

Degenerate collagen surrounded by eosinophilic inflammatory cells - FLAME FIGURE
Eosinophilic granuloma

Severe eosinophilic infiltrates of the skin associated with indolent ulcer
Describe this lesion found on a horse.

Severe collagen degeneration associated with collagenolytic granuloma
Where on the horse would you find eosinophilic lesions?
Axialla
Lateral trunk
(collagenolytic are spread about)
Epithelial tumours
Keratinocyte derived
Cutaneous adnexal tumours
Keratinocytes of follicles and glandular tissue
Describe this lesion

Focal, well demarcated 2x2cm round lesion. Encalsulated friable material.
Subacute focal moderate keratinous dermal cyst

Exophytic
Hyperkeratotic, hyperplastic epithelial growth
Dermal stalks support
Papilloma - caused by papillomavirus
Koilocytes
keratinocytes with eccentric pyknotic nucleus and peripheral clear halo (ballooning degeneration)

Describe

Ulcerated exophitic mass.
Dermal neoplasia
Squamous cell carcinoma

Keratin pearls often associated with squamous cell carcinoma

Poor demarcation
Locally invasive
Anisocytosis, anisokaryosis
Multiple mitosis

Basal cell tumour
Small hyperchromic nuclei
High mitotic index
INFUNDIBULAR KERATINISING ACANTHOMA

Infundibular differentiation with keratohyalin granules in the granular layer
Central lumen filled with keratin surrounded by squamous epithelial cells and collagen

TRICHOLEMMOMA
Clear keratinocytes similar to the isthmic outer root sheath cells
Benign, originating from the external hair root sheath

PILOMATRICOMA
Derrived from follicular matrix cells
Appear chalky white on cut surface
Benign
Signs of matrical differentiation as seen in the hair bulb
Ghost cells - eosinophilic anuclear cells

Trichoepithelioma

Neoplastic proliferation of all three layers of the hair follicle
Multinodular cream masses
Hyperplasia of follicular epithelium, hyperkeratosis

Trichblastoma
Germ cell proliferation

Sebaceous gland adenoma - similar construction to sebaceous gland - vacuolated (fatty) cells with peripheral nucleus

Sebaceous epithelioma
Few sebocytes - lots of basal cells
A common perianal tumour found in dogs
Perianal adenoma - modified sebaceous gland neoplasia
What type of hepatoid gland tumour is shown here?

Highly organised, well-demarcated, little pleomorphism (well differentiated)
Adenoma
What type of hepatoid gland tumour is shown here?

Disorganised lobular pattern
Higher cellular atypia and mitotic index
Local invasion
What type of apocrine tumour is seen here?

Adenoma - well differentiated (non-encapsulated), little mitosis and pleomorphism

Fibroma - characterised by streams of well differentiated fibrocytes and collagen


Sarcoid - fibroblast tumour
Biphasic tumour: both an epidermal and a dermal component, although the connective tissue is the preponderant proliferating tissue

Streams of neoplastic cells, infiltration into muscular tissue. Lymphocytic inflammation.
Pleomorphic and mitotic cells

Myxoma
Tumour originating from primitive fibroblasts
Loosly arranged spindloid cells

Describe this lesion

Focal ulcerated red raised lesion, exudative
Cutaneous haemangiopericytomat - whorls of neoplastic cells surround vessels

Describe this lesion

Non-encapsulated, well-circumscribed dermal or subcutaneous nodule formed by the confluence of dilated blood-filled channels lined by flattened endothelium.
Dermal haemangioma
Describe the lesions seen in this slide

Anisocytosis
Anisokaryosis
Pleomorphic cells
Mitosis
Aberent vascular channels
Haemangiosarcoma
Describe the histological changes associated with lipoma
Resembles normal adipose tissue
Infiltrative lipomas also resemble normal tissue but infiltrate between muscle fibres - rare

Pleomorphic vacuolated fatty cells
Liposarcoma
Histiocytoma
Derived from langerhanns cells - dentritic immunological cells
Often single domed mass which regress with lymphocyte infiltration
Describe this lesion

Non-encapsulated, pleomorphic, highly mitotic cells with close association with eosinophils.
Plasmacytic differentiation may occur: Perinuclear halo, Russel bodies, Amyloid

Calcinosis cutis
Caused by hyperadrenocorticism
Widespread dermal mineralisation of collagen and basement membrane

Calcinosis circumscripta
Localised mineralisation of dermis
Dermal lakes and inflammation in acute and fibrosis and metaplasia of cartilage in chronic lesions
