Histopath-Jager-Ch2: General Reactions of the Skin to Injury Flashcards
What is epidermal hyperplasia?
Increase in the number of nucleated cells
How many nucleated layers thick is a normal epidermis in the dog and cat?
No more than 2 layers thick
What is acanthosis?
Hyperplasia of stratum spinosum
What are rete ridges?
Folds of epidermis from increased thickening of stratum spinosum, which penetrate into the superficial dermis.
Which body locations have rete ridges normally?
Footpads, nasal planum, and scrotal skin (lesser extent)
T/F Epidermal hyperplasia indicates chronic lesions.
False. Can be seen as early as 36-48 hours after superficial traumatic injury.
What are the 4 types of epidermal hyperplasia? Which is the most common?
Irregular epidermal hyperplasia (most common) Regular epidermal hyperplasia Papillated epidermal hyperplasia Pseudocarcinomatous epidermal hyperplasia
What is irregular epidermal hyperplasia?
Hyperplastic changes in which the rete ridges formed are uneven in shape and height. Most common form.
What is regular epidermal hyperplasia?
Even width and depth. Tips may be club shaped. Uncommon. May point towards specific diseases (ex lichenoid psoriasiform dermatosis of springer spaniels).
What is papillated epidermal hyperplasia?
Digitate projections of the epidermis, as in warts or papillomas. Also seen with seborrheic dermatitis and callosities.
What is pseudocarcinomatous epidermal hyperplasia?
Extreme, irregular epidermal hyperplasia. Branched and fused rete ridges have superficial resemblance to invasive SCC. May have numerous mitotic figures, but does not demonstrate atypia of malignant cells. No invasion through BMZ. Seen at border of chronic ulcers and overlying various suppurative, granulomatous or neoplastic processes.
What is hypergranulosis?
Increase in width of stratum granulosum
What is orthokeratotic hyperkeratosis?
Increased thickness of stratum corneum. Represents either increase in production of keratin or decrease in normal attrition of cornified layer.
How many layers should you be able to see in a normal stratum corneum on H&E staining?
7-10 layers.
What types of diseases should you consider if you see orthokeratotic hyperkeratosis in the absence of acanthosis?
Disorders of keratinization, corneocyte adhesion or endocrine-related dermatoses.
What are the three major types of orthokeratotic hyperkeratosis?
Basket-weave
Compact
Laminated
What is basket-weave orthokeratotic hyperkeratosis?
Excess of normal type of keratin. Typical of endocrine, primary seborrhea and dermatophytosis
What is compact hyperkeratosis?
Normally found only on areas of the body where there is likely to be wear and tear, such as the footpads. The normal basket-weave keratin may be replaced with the more protective compact keratin when the skin surface is subjected to chronic low-grade trauma, such as persistent licking.
What is laminated orthokeratotic hyperkeratosis?
Seen in few diseases of abnormal keratinization. Ex. ichthyosis.
What is parakeratotic hyperkeratosis?
Thickened stratum corneum in which the nuclei of ther keratinocytes are retained.
Indicates failure of normal epidermal differentiation.
Ex. zinc-responsive dermatoses, thallium toxicosis, superficial necrolytic dematitis, lethal acrodermatitis of bull terriers and some seborrheic diseases (Malassezia dermatitis)
What is dyskeratosis?
Premature keratinization of cells of stratum spinosum.
Hypereosinophilic cytoplasm, degenerative changes to nucleus.
Dyskeratosis can be difficult to distinguish between which other keratinocyte abnormality?
What can help you differentiate between the two?
Apotosis.
Dyskeratosis seen more often in conjunction with diffuse parakeratosis (altered epidermal differentiation).
Apoptosis seem more often in conjunction with hydropic interface dermatitis or satellitosis.
What diseases could be suspected with dyskeratosis?
Zinc-responsive disease, some vit A dermatoses, some epidermal neoplasms (esp SCC)
What is spongiosis?
Intercellular edema in the epidermis
Describe epidermal pallor.
What two conditions does this finding make you suspicious for?
Edema, typically within stratum spinosum.
Swollen cells with very pale eosinophilic cytoplasm.
May see peripherally displaced nucleus.
Seen with zinc-related disorders and is characteristic to hepatocutaneous syndrome.
What term would you use for pale-staining, swollen keratinocytes in pox viral infections in several species?
Ballooning degeneration.
What is hydropic degeneration? Where would it be found?
Intracellular edema with presence of one or more clear vacuoles within cytoplasm. Usually restricted to cells of the stratum basale of epidermis and outer root sheath of follicle.
In which diseases is hydropic degeneration commonly seen?
Lupus erythematosus, lichenoid dermatoses, drug eruption, dermatomyositis
What are some consequences of epidermal edema?
- Spongiosis often leads to the formation of spongiform vesicles
- Intracelllular edema may lead to reticular degeneration and formation of multilocular vesicles
- Hydropic degeneration may lead to formation of intra- and subepidermal clefts or vesicles
How do you differentiate between microvesicles, vesicles, and bullae?
Microvesicles - inapparent to naked eye
Vesicle <1cm
Bulla >1cm
What are some changes that can lead to vesicles and bullae?
Spongiosis
Intracellular edema
Hydropic degeneration of basal keratinocytes
Acantholysis
Physicochemical damage to BMZ by heat, friction or freezing
Immune mechanisms disruptin the DE adhesions (as in BP)
Genetic defects in structural molecules (hemidesmosomal complexes, anchoring filaments)
T/F Vesicles and bullae are common in feline and canine dermatoses.
False. Uncommon. The thinness of the normal epidermis results in rapid rupture of any vesicles or bullae formed. Diseases like BP that cause vesiculobullous lesions in people usually present with extensive ulceration in animals.
What is the term for vesicles containing substanial numbers of leukocytes?
Vesicopustules
What are clefts?
Empty, slit-like spaces that form within the epidermis or at the DE junction.
What is acantholysis?
Loss of cohesion amoung viable keratinocytes, leading to formation of clefts, vesicles or bullae
What is the difference between vesicles/bullae and clefts?
Vesicles/bullae are fluid-filled, clefts are empty
Describe the appearance of an acantholytic keratinocyte.
Round shape, hypereosinophilic cytoplasm, morphologically normal nucleus
What type of pustules are common in the dog?
Neutrophil-rich
What type of pustules are typical of staphylococcal pyoderma
Spongiform pustules - multilocular accumulations of neutrophils among the keratinocytes of the outer stratum spinosum and granulosum.
What are Munro’s microabscesses?
Desiccated accumulations of neutrophils in the stratum corneum
What are Pautrier’s microabcesses?
Contain cytologically atypical lymphocytes. Virtually pathognomonic for epitheliotropic lymphoma.
In what conditions might you see small spongiotic foci containing mononuclear cells?
Atopic dermatitis and seborrheic disorders
What is a crust?
Reflects a previous epidose of exudation.
Desiccated conglomeration of clotted plasma proteins, leukocytes, erythrocytes, epithelial squames and often microorganisms.
What are 5 different types of crust? What is most common?
- Serous crust - eosinophilic proteinaceous coagulum representing plasma
- Haemmorrhagic crust - RBCs. Beware of overinterpretting contamination from bx procedure
- Cellular crust - degenerate leukocytes, usually neutrophils
- Serocellular crust - mix of plasma and leukocytes - most common type of crust in exudative lesions
- Palisading crust - crust is organized into horizontal strata. Reflects episodic bursts of leukocytic exocytosis, pustule formation and/or parakeratosis.
Which type of crust is typical for dermatophytosis?
Palisading crust
What is exocytosis?
Migration of leukocytes and erythrocytes into the epidermis
Which cytokine is constitutively produced by keratinocytes?
IL-1
Describe the appearance of apoptotic keratinocytes.
Shrunken, hypereosinophilic cytoplasm, fragmented (karyorrhectic) or pyknotic nuclei.
In which layer of the epidermis is apoptosis most commonly seen?
Basal cell layer, but may occur at any level.
What is satellitosis?
Clustering of mononuclear cells, most probably cytotoxic T-lymphocytes, around dead keratinocytes. Apoptosis is induced by the T-cells.
What are colloid bodies?
Fragments of apoptotic keratinocytes which escape phagocytosis and lie, surrounded by basement membrane, in the upper dermis.
What are 4 mechanisms for which hyperpigmentation can occur?
Increase rate of melanosome production
Increase in melanosome size
Increase in degree of melanization of the melanosome
Increase in number of melanocytes (chronic sunlight exposure)
What are lentigenes?
Focal, hyperpigmented macules resulting from melanocytic hyperplasia and increased melanin production.
Congenital lesions on MC junctions in orange, cream and tricolored cats.
What is the term for the presence of melanin within the dermis?
Pigmentary incontinence
Describe dermal edema
Very pale-staining dermis due to separation of collagen bundles by edematous interstitium. Separation of the bundles of collagen may be severe enough to produce a web-like effect, likened to gossamer.
May see dilation of lymphatics.
Describe the appearance of granulation tissue.
Proliferation of fibroblasts and BVs with prominent endothelia.
BV grow perpendicularly to skin surface
Newly laid down collagen fibers and fibroblasts are oriented roughly parallel to skin surface.
Typically seen in repairing ulcers.
What is fibrosis?
Replacement of normal collagen with increased connective tissue. Increased # of collagen bundles, usually of smaller diameter and more densely packed than normal dermal collagen, and an increased # of fibroblasts.
How is sclerosis characterized?
Large, hypereosinophilic, somewhat hyaline collagen bundles and reduced numbers of fibroblasts.
May represent scar or failure of normal collagen fiber turnover.
With what condition is cutaneous amyloidosis most frequently seen?
Cutaneous plasmacytomas.
Also described as a cutaneous manifestation of systemic amyloidosis.
Which stain can be used to demonstrate amyloid?
Congo red stain
What stain can be used to demonstrate lipid deposits?
Oil red O
Where are cholesterol clefts most commonly seen?
In areas of inflammation targeting ceruminous glands of the ear, but may occur in cutaneous xanthomas, traumatic panniculitis and feline pansteatitis induced by Vit E deficiency.
What are flame figures?
Deposits of eosinophilic debris, presumably the contents of degranulated eosinophils, on hyaline-appearing collagen bundles in the dermis.
In what conditions are flame figures commonly seen?
Eosinophilic collagenolytic disease in the cat, such as linear granuloma, and in arthropod bite-reactions.
Describe the appearance of dystrophic mineralization.
Basophilic granular deposits of mineral salts on collagen bundles.
What is the term for extrusion of foreign material or altered endogenous substances, such as mineralized collagen bundles, to the skin surface through the surface epidermis or through the follicular epithelium.
Transepidermal elimination
T/F Collagen changes on histopathology of patients with Ehlers-Danlos syndrome can be difficult to identify.
True. These disorders have dramatic clinical consequences, but histological lesions are often subtle and are rarely sufficiently convincing to be diagnostic.
What are two stains that can be used for elastin?
orcein-Giemsa
Verhoeff’s elastin
What is the term for an increase in dermal glycosaminoglycans?
Mucinosis
What stains can be used to demonstrate mucinosis?
Colloidal iron (blue or green), toluidine blue, and alcian blue (blue).
What are some diseases in which mucinosis (secondary to increased fibroblast secretory activity) is prominent?
Canine hypothyroidism, acromegaly, canine lupus erythematosus, T-cell lymphoma
Marked follicular hyperkeratosis is seen in which diseases?
Primary seborrhea, Vit A responsive seborrhea, follicular dystrophy, feline acne, canine demodicosis, endocrine-related dermatoses, some forms of sebaceous adenitis and Schnauzer comedo syndrome
Name three different morphological expressions of fat necrosis. Which is the most common?
- Microcystic fat necrosis - most common
- Hyalinizing fat necrosis
- Mineralizing fat necrosis
How is microcystic fat necrosis characterized?
Small, round microcysts, which are often at the center of pyogranulomas.
Form from lipid released from the degenerating lipocytes or by confluence of necrotic lipocytes
How is hyalinizing fat necrosis described? For which diseases is this typical?
Lipocytes converted into a feathery, eosinophilic amalgam trapping scattered fat microcysts.
Typical for lupus panniculitis and rabies-induced vaccine reactions in dogs.
How is mineralizing fat necrosis characterized? In which condition is it most commonly seen?
Deposition of irregular, granular, basophilic granules, often in the peripheral cytoplasm of the necrotic lipocytes.
Seen in pancreatic panniculitis and some cases of traumatic panniculitis.
