L2 - Dermatohistopathology PDF

Integumentary system: Lecture 1 Contents ❑ General Functions VETERINARY PATHOLOGY II ❑ SYSTEMIC VPM 3419: ❑ Normal structure INTEGUMENTARY ❑ Dermatohistopathology SYSTEM - Epidermal changes - Dermal changes - Subcutaneous cha...

Integumentary system: Lecture 1 Contents ❑ General Functions VETERINARY PATHOLOGY II ❑ SYSTEMIC VPM 3419: ❑ Normal structure INTEGUMENTARY ❑ Dermatohistopathology SYSTEM - Epidermal changes - Dermal changes - Subcutaneous changes VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II Integumentary system: Lecture 1 Contents ❑ General ❑ Functions ❑ Normal structure ❑ Dermatohistopathology - Epidermal changes - Dermal changes - Subcutaneous changes VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  General 40% ❑ The largest of the body system & forms an anatomic boundary between the animal and its external environment. ❑ Skin diseases: common cases in SA practice, can be an indicator of systemic diseases, considerable economic losses in food-producing animals & zoonosis. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  Functions ❑ Protection / barrier: protection against ultravoilet light, mechanical, chemical and thermal insult and acts as an effective barrier to the loss of water, electrolytes and macromolecules, and to the invasion of microrganisms. ❑ Sensation: contains a variety of receptors for touch, pressure, pain and temperature. ❑ Thermoregulation: hairs and subcutaneous adipose tissues insulated the body against heat loss, whilst excess heat can be evaporated through sweat and an increased blood flow of the dermis. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  Functions ❑ Metabolic functions: subcutaneous adipose tissue constitutes a major store energy (triglycerides). Epidermis synthesizes Vitamin D. ❑ Motion, shape, colour: the flexibility, elasticity and toughness of the skin allow motion and provide shape and form. Process in skin (melanin formation, vascularity and keratinization) help determine the coat and skin colour. Pigmentation of the skin prevents damage from solar radiation. ❑ Indicator: may be important indicator of internal diseases. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  Skin structure ❑ Composed of epidermis, dermis, hair follicle, adnexal glands and subcutis (hypodermis). VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II Skin structure VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  Epidermis, Dermis and Hypodermis epi- VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II Skin structure EP: epidermal peg DP: Dermal papilla VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  Epidermis ❑ Epidermis: production of horny layer 1. Stratum basale (basal layer): a single layer of cell; cuboidal or columnar. Mitosis is rarely seen in normal animal partly because of low turnover. 2. Stratum spinosum (prickle layer): several layers of polygonal cells. 3. Stratum granulosum (granular layer): 1 or more cells thick which composed of nucleated, flattened keratinocytes. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  Epidermis 4. Stratum lucidum (clear layer): a thin band of flattened, unstained cells (occurs in footpad skin and Provide better clusive miss between the shin nasal planum). - no heir folick-> 5. Stratum corneum (horny layer): many layers of dead, fully keratinized, flattened cells. ❑ The progeny of the basal cell layer undergo differentiation during their outward migration, to synthesize keratins and slough off at the skin surface. ❑ In addition to keratinocytes, the epithelium consists 3 types of dendritic cells: melanocytes, Langerhan's cells and indeterminate cells. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II Skin structure VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II Skin structure VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II Melanin and keratohyalin granules VPM 3417: VETERINARY PATHOLOGY III VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  Epidermal appendages (adnexa) 1. Hair follicles ❑ Simple hair follicles (eg. cattle and horses). ❑ Compound hair follicles (eg. sheep, goats, dogs and cats). ❑ Hair follicles undergo cyclic growth: anagen (actively growth), catagen (transtional), telogen (resting). VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  Hair follicle The structure from which the hair grows. Parts: internal root sheath, external root sheath and at the base the dermal papilla and germinal matrix. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II Hair follicle VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II Hair follicle VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  Hair follicle Hair with epithelial root sheaths (ORS & IRS). Cross section of a hair with a sebaceous gland. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  Epidermal appendages (adnexa) 2. Glands of skin ❑ Sebaceous glands: holocrine that develop as part of the follich. hair follicle complex. adjacent tohair -sebum (triglyceride+cholesterol) ❑ Apocrine sweat glands@epitrichial: also develop as part of the hair follicle complex which opens via excretory ducts into the pilary canal of the hair follicles. -fatty sweat secretion (thick clear) -solely effective in hoofed animals like horses, camels, donkeys ❑ Eccrine sweat glands@atrichial: open directly to the epidermal surface - merocrine secretion. -water+salt (thin watery clear) -dogs, cats (pads/paws) VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  QUESTION: Glands of skin? Hair follicle? 2 Sebaceous gland 1 Sweat gland Compound hair follicle VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  Epidermal appendages (adnexa) 3. Dermis (Corium) bes Br ishem ❑ Support and nourish the epidermis and appendages. ❑ Composed of collagen, reticulin (immature collagen) and elastin fibres embedded in a glycosaminoglycan- rich ground substance. ❑ In addition to fibroblasts; dermis + for mast cells, mononuclear cells: lymphocytes and macrophages (a few), eosinophil and neutrophil (rare). ❑ Superficial dermis has finer fibres than the deep dermis. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  Dermis Dermis: consists of 2 layers: (1) Papillary Layer: subepithelial loose connective tissue. (2) Reticular Layer: dense connective tissue deep to papillary layer; contains epidermally derived hair, sweat and sebaceous glands. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  Epidermal appendages (adnexa) 4. Hypodermis (Subcutis) ❑ Heat insulator + give body contour. ❑ Composed of lipocytes, blood vessels, nerves and connective tissue. ❑ Cutaneous vasculature: superficial, middle and deep. Nerve fibers in general follows blood vessels, whilst lymphatic present in the superficial dermis. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  Nerves Sympathetic autonomic nervous system Light touch, heat Itch, pain, touch, pressure, temperature Pressure, mechanoreceptor Arterioles, APM, apocrine Eccrine VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  Types of skin ❑ Normal: differ - species and locations (e.g. location: thin & thick skin; skin of ventral abdomen vs. paw or nasal planum) VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  Types of skin ❑ Normal: differ - species and locations (e.g. location: thin & thick skin; skin of ventral abdomen vs. paw or nasal planum) -Thin skin = thin epidermis VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  SUMMARY / REVISION Histology of Skin: https://www.youtube.com/watch?v=acXjaANVK4M Thin Skin Histology: https://youtu.be/-KmfEbKmKFw Thick skin Histology: https://www.youtube.com/watch?v=IQOkSF4rYrs VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  VPM 3417: VETERINARY PATHOLOGY III VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II Dermatohistopathology Contents ❑ 1. Epidermal changes ❑ 2. Dermal changes ❑ 3. Subcutaneous changes VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Epidermal changes ❑ Hyperkeratosis: increase thickness of the stratum corneum. may be absolute (common) or relative (rare). - absolute: actual increase in thickness - relative: apparent increase due to thinning of underlying epidermis Further specified as orthokeratotic (anuclear) and parakeratotic (nucleated). Generalised (horizontal layer) or Focal (vertical defect). VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Epidermal changes ❑ Hyperkeratosis: Often nondiagnostic findings, chronic stimuli (superficial trauma, inflammation, sun exposure). - Diffuse parakeratotic hyperkeratosis is most consistent with eg. Ectoparasitism, dermatophilosis, dermatophytosis, Malassezia dermatitis and zinc responsive dermatoses. - Diffuse orthokeratotic hyperkeratosis suggests nutritional deficiencies, seborrheic dermatitis, developmental abnormalities (ichthyosis, follicular dysplasia). VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Epidermal changes ❑ Hypokeratosis: decrease thickness of the stratum corneum (less common). exceptionally rapid epidermal turnover time, reduced cohesion or both, between cells of stratum corneum. Exfoliative or seborrheic skin disorders (excessive surgical prep, topical medicaments, friction on intertriginous areas). VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Epidermal changes ❑ Dyskeratosis: premature and faulty keratinization of viable cells (st. spinosum). Shrunken cell, separated from adjacent keratinocytes, pyknotic nuclei & brightly eosinophilic cytoplasm (accumulation of keratin filaments) [difficult to distinguish from necrotic keratinocytes] eg. papilloma, squamous cell carcinoma, seborrheic complexes. ❑ Hypergranulosis / hypogranulosis: increase or decrease thickness of the stratum granulosum: common but undiagnostic. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II Epidermis, Dermis and Hypodermis HYPERKERATOSIS VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II Epidermis, Dermis and Hypodermis HYPOKERATOSIS Butler et al., 2012 VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II Epidermis, Dermis and Hypodermis DYSKERATOSIS VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Epidermal changes ❑ Hyperplasia/Acanthosis: increase thickness of the noncornified epidermis due to an increase number of epidermal cells. Acanthosis specifically indicates an increase thickness of the stratum spinosum. ❑ Hypoplasia/atrophy: decrease thickness of the noncornified epidermis due to decrease no. of cells (hypoplasia) or decrease size of cells (atrophy). eg. Hyperadrenocorticism. ACANTHOSIS EPIDERMAL ATROPHY VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Epidermal changes ❑ Necrosis / Necrolysis: death of cells or tissues. Nuclear changes; karyorrhexis, pyknosis and karyolysis. Keratinocytes loss of intercellular bridges and cytoplasm eosinophilic. Coagulation or caseation. ▪ Focal: drug eruption, microbial infections. ▪ Generalised: vasculitis, immunological. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  Epidermis, Dermis and Hypodermis ❑ Intercellular oedema (spongiosis): widening of the intercellular bridges of the epidermis (eg. acute or subacute dermatosis). spines VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Epidermal changes ❑ Intracellular oedema: increase size, cytoplasmic pallor and displacement of the nucleus peripherally. May be confused with artifacts (eg. freezing, delayed- fixation artifacts). Ballooning degeneration: specific feature of viral infection. Cytoplasm: swollen & eosinophilic, but without vacuolation. Nuclei; enlarged or condensed & occasionally multiple. Hydrophic degeneration: intracellular oedema of the stratum basale. Usually associated with eg. lupus erythematosus, drug eruptions. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Epidermal changes ❑ Acantholysis: loss of cohesion between epidermal cells resulting in intraepidermal clefts, vesicles and bullae; may be caused by eg. severe spongiosis, ballooning degeneration, proteolytic enzymes. ❑ Exocytosis: migration of inflammatory cells and/or erythrocytes through the intercellular spaces of the epidermis (eg. inflammatory dermatosis, vasculitis, coagulation defect). VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II Pustule and Acantholysis Acantholysis = loss of cohesion between keratinocytes. Eg. Pemphigus foliaceous VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Epidermal changes ❑ Clefts (lacunae): slit-like spaces that do not contain fluid within the epidermis or at the dermoepidermal junction; may be caused by acantholysis or hydropic degeneration of the basal cells, although it may also be handling artifacts. cleft - V flut Cyst > - X fluid VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Epidermal changes ❑ Microvesicles, vesicles, bullae (blisters): macroscopic or microscopic fluid-filled, relatively acellular spaces within or below the epidermis. Caused by eg. Ballooning degeneration, acantholysis, subepidermal oedema, intracellular or intercellular oedema. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II 1. Epidermal changes ❑ Vesicle VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Epidermal changes ❑ Microabscesses, pustules: macroscopic or microscopic intraepidermal and subepidermal; cavities filled with inflammatory cells. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II Pustule Subcorneal pustule with numerous acantholytic cells admixed with neutrophils. Eg. Pemphigus foliaceous VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Epidermal changes ❑ Hyperpigmentation (hypermelanosis): excess melanin deposited within the epidermis, and often concurrently, in dermal melanophages. Focal or diffuse. Causes: chronic inflammatory dermatoses, developmental or neoplastic disorders. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Epidermal changes ❑ Hypopigmentation (hypomelanosis): decrease melanin in the epidermis. Congenital or acquired idiopathic defects in melanization. Eg. Vitiligo, leukoderma, toxic (monobenzyl ether in rubbers or plastic), inflammatory disorders (lupus erythematosus). VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Epidermal changes ❑ Crust: consolidated, desiccated surface mass composed of varying combination of keratin, serum, cellular debris, and often microorganisms. Crusts; serous (serum), haemorrhagic (blood), cellular (inflammatory cells), serocellular (exudative: serum + inflammatory cells). VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Epidermal changes ❑ Horn cysts (keratin cysts): circular cysts structures surrounded by flattened epidermal cells and containing concentrically arrange lamellar keratin (eg. basal cell tumors). VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  1. Epidermal changes ❑ Horn pearls (squamous pearls): focal, circular, concentric layers of squamous cells showing gradual keratinization toward the centre, often accompanied by dyskeratosis (eg. squamous cell carcinoma). VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  2. Dermal changes ❑ Dermal collagen: Examples Collagen hyalinization; confluence and increase eosinophilic, glassy, refractile appearance eg. chronic inflammation. Fibrinoid degeneration; deposition on or replacement with a brightly eosinophilic fibrillar or granular substance resemble fibrin (eg. connective tissue disease). Other changes: lysis, degeneration, dystrophic mineralization and atrophy. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  2. Dermal changes ❑ Fibroplasia, fibrosis, sclerosis: formation and development of fibrous tissue in increase amounts (granulation tissue). Fibrovascular proliferation, prominent fibroblast. Edema and inflammatory cells are constant features of fibroplasia. Fibrosis is a later stage of fibroplasia; fibroblasts and collagen fibrils increase, whilst sclerosis (scar) may be end point of fibrosis; collagen fibrils increase, but fibroblast reduced. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  2. Dermal changes ❑ Exuberant Granulation Tissue Vertically oriented capillaries (C) and horizontally oriented fibroblasts, few collagen fibres provide a ‘lattice-work’ appearance to granulation tissue. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  2. Dermal changes ❑ Papillomatosis: projection of dermal papillae above the surface of the skin, resulting in an irregular undulating configuration of the epidermis. Often associated with epidermal hyperplasia (eg. chronic inflammation & neoplasm). VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  2. Dermal changes ❑ Pigmentary incontinence: presence of melanin granules free within the subepidermal dermis, and within dermal macrophages (melanophages). VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  2. Dermal changes ❑ Dermal oedema: dilated lymphatics, widened perivascular and interstitial spaces. ❑ Mucinous degeneration: increase amounts of an amorphous, stringy, granular, basophilic material that separates, thins or replaces dermal collagen fibrils and surround blood vessels and appendages (eg. Canine hypothyroidism). VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  2. Dermal changes ❑ Follicular epithelium: Follicular keratosis, plugging and dilatation. Others; perifolliculitis, folliculitis, follicular atrophy (eg. hormonal disease). ❑ Sebaceous, apocrine sweat glands: suppurative and granulomatous inflammations (sebaceous adenitis, hidradenitis). May become atrophic, cystic (hormonal) or hyperplastic (chronic inflammation). ❑ Cutaneous blood vessels: eg. dilatation, endothelial swelling, hyalinization, vasculitis, thromboembolism. VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II  3. Subcutaneous changes ❑ Subcutaneous fat: suppurative and granulomatous dermatoses, inflammatory changes (eg. Panniculitis, steatitis) and necrosis. tumom also VPM 3419: SYSTEMIC VETERINARY PATHOLOGY II Circulatory disturbances VPM 3417: VETERINARY PATHOLOGY III