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1
Q

What are the four layers of the epidermis - in order.

A
  1. Stratum basale - basal layer
  2. Stratum spinosum - spinous layer
  3. Stratum granulosum - granular layer
  4. Stratum corneum - cornified layer
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2
Q

Where is the skin the thinnest?

A

Inguinal and axillary regions

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3
Q

What is unique about scrotal skin histologically?

A
  1. Thicker than haired skin
  2. Rete ridges
  3. Epidermal pigmentatin is prominent
  4. Few pilosebaceous units
  5. Smooth muscle bundles present in the dermis
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4
Q

What is unique about the footpads histologically?

A
  1. Very thick
  2. Marked rete ridge formation
  3. Multilayered stratum spinosum
  4. Two-or-three cell thick stratum granulosum
  5. Wide, compact stratum corneum
  6. No pilosebaceous units
  7. Atrichial (eccrine) glands present in panniculus
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5
Q

What is unique about the nasal planum histologically?

A
  1. Thick epidermis
  2. Rete ridges
  3. Laminated stratum corneum
  4. Thin or absent stratum granulosum
  5. Melanotic stratum spinosum
  6. No hair follicles or pilosebaceous units
  7. Prominent nerves and vessels
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6
Q

What are some tips to obtain a good biopsy?

A
  • Multiple biopsies from several sites
  • Primary lesions are much better than secondary
  • 6mm or excisional biopsy are ideal
  • Minimize operator-induced artifact
  • Don’t surgically prepare the sites
  • Give signalment, history, DDX, etc
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7
Q

Define epidermal hyperplasia.

A

Increase in the number of nucleated cells in the epidermis.

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8
Q

Define acanthosis

A

Epidermal hyperplasia, specifically hyperplasia of the stratum spinosum.

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9
Q

Does epidermal hyperplasia always indicate chronicity?

A

No.

Even superficial traumatic injury - like tape stripping - can induce a burst of mitotic activity in the transient amplifying cell population that results in acanthosis by 36-48 hours. You will probably see mitotic figures in the basal layer.

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10
Q

What are the four morphological types of epidermal hyperplasia?

A
  1. Irregular
  2. Regular
  3. Papillated
  4. Pseudocarcinomatous
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11
Q

Define irregular epidermal hyperplasia

A

Hyperplastic changes in which the rete ridges formed are uneven in shape and height. This is the most common form of epidermal hyperplasia.

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12
Q

Define regular epidermal hyperplasia

A
  • Rete ridges are even in width and depth
  • Uncommon
  • Seen with lichenoid psoriasiform dermatosis of springer spaniels
  • In humans, regular epidermal hyperplasia = psoriasiform hyperplasia
    • Seen with psoriasis
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13
Q

Define papillated epidermal hyperplasia

A

Digitate projections of the epidermis

Seen with warts and papillomas

Seborrheic dermatitis

Callous

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14
Q

What is pseudocarcinomatous epidermal hyperplasia?

A

Extreme, irregular epidermal hyperplasia which is branched and fused. There are a bunch of rete ridges which branch and link up.

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15
Q

Define hypergranulosis

A

Increase in the width of the straytum granulosum

You will see a more dark blue granules of keratohyalin.

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16
Q

What is orthokeratotic hyperkeratosis?

A

Increased thickness of the stratum corneum

It is either because of an increase in the production of keratin, or a decrease in the normal attrition of the cornified layer.

Usually there is about 7-10 layers; don’t overinterpret this. In real life, there are usually 40+ layers to the stratum corneum.

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17
Q

If you see orthokeratosis without acanthosis, what should you suspect?

A

Disorders of keratinization, corneocyte adhesion or endocrine-related dermatoses.

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18
Q

What are the three morphological types of orthokeratotic hyperkeratosis?

A
  1. Basket-weave orthokeratosis
  2. Compact orthokeratotic hyperkeratosis
  3. Laminated orthokeratotic hyperkeratosis
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19
Q

What is basket weave orthokeratosis?

A

Excess of the normal type of keratin covering the haired parts of the body. This is an artifact of fixation. You will see this type of hyperkeratosis in endocrine skin disease, primary seborrhea or dermatphytosis.

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20
Q

What is compact orthokeratotic hyperkeratosis?

What is your top differential for it?

A

Loss of the basket weave, thick and packed keratin.

Seen with chronic low-grade trauma (licking) or on the footpads.

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21
Q

What conditions do you see laminated orthokeratotic hyperkeratosis?

A

Ichthyosis

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22
Q

What is parakeratotic hyperkeratosis? What does it indicate?

A

Thickened stratum corneum in which the nuclei of the keratinocytes are retained. Excess production of abnormally keratinized stratum corneum.

Indicates a failure of normal epidermal differentiation.

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23
Q

Give five examples of conditions where parakeratotic hyperkeratosis is seen.

A
  1. Zinc-responsive dermatosis
  2. Thallium toxicosis
  3. Superficial necrolytic dermatitis (hepatocutaneous)
  4. Lethal acrodermatitis of bull terriers
  5. Seborrheic diseases like Malassezia dermatitis
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24
Q

What is dyskeratosis?

A

Refers to premature keratinization of cells in the stratum spinosum. Often occurs in combination with parakeratosis - indicating an abnormality of epidermal differentiation.

This can be difficult to distunguish from apoptosis. The dyskeratotic keratinocytes have hypereosinophilic cytoplasm and degenerative changes of the nucleus. You should look at the picture as a whole to determine if apoptosis vs. dyskeratosis.

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25
What are some conditions where you might expect epidermal dyskeratosis?
1. Zinc-responsive dermatosis 2. Some Vitamin A responsive dermatoses 3. Epidermal neoplasia like SCC
26
What is another word for (INTERCELLULAR) epidermal edema?
Spongiosis Spongiosis is refers to intercellular edema of the epidermis. Named for the spongy appearance which results from the separation of keratinocytes between edema fluid.
27
What does INTRAcellular epidermal edema represent?
Degenerative changes of the actual keratinocyte
28
What does epidermal pallor indicate?
This describes an edematous change that will usually affect the cells of the stratum spinosum. The affected cells are swollen with very pale eosinophilic cytoplasm. It doesn't look like vacuoles, the cells just look a bit more eosinophilic. You see this with zinc-responsive dermatosis and SND.
29
What is ballooning degeneration?
Swollen, acantholytic keratinocytes Pale-staining swollen keratinocytes Not common - pox virus, viral lesions
30
Discuss vacuolar alteration of the epidermis
This refers to multiple small vesicles above and below the basement membrane zone. Can be artifact, or a non-specific finding.
31
How do you differentiate a vesicle, bullae or microvesicle?
Vesicles \< 1 cm Bullae \> 1 cm Microvesicle - can't see with naked eye Can be see within the epidermis at any level or at any level of the dermoepidermal junction.
32
What is a cleft?
Empty, slit-like spaces that form within the epidermis or at the dermoepidermal junction. These occur at areas of weakened keratinocyte adhesion between adjacent cells or between basal cells and basal lamina. Artifactual clefts usually occur at the edges of samples.
33
What is acantholysis?
Loss of cohesion among viable keratinocytes which an lead to formation of clefts, vesicles or bullae. Often markers for immune-mediated lesions. Loss of adhesion junctions.
34
What are pustules?
Intraepidermal or subepidermal accumulations of inflmmatory cells and fluis.
35
What is a Munro microabscess?
Desiccated accumulations of neutrophils in the stratum corneum. Suggestive of supefcicial microbial infection.
36
When do you tend to see eosinophilic pustules?
Parasitic diseases Can also see with allergic, immune-mediated, microbial (Malassezia) and idiopathic skin diseases (sterile eosinophilic pustulosis).
37
What is Pautrier's microabscess? What disease do you see these with?
Mononuclear pustule. These microabscesses will contain cytologically atypical lymphocytes. = CTCL
38
What is a crust? What are the types?
Previous episode of exudation. Desiccated conglomeration of clotted plasma proteins, leukocytes, erythrocytes, epithelial cells, +/- microorganisms. 1. Serous crust 2. Hemorrhagic crust 3. Cellular crust 4. Serocellular crust 5. Palisading crust (dermatophytosis)
39
What is exocytosis?
Migration of leukocytes and erythrocytes into the epidermis.
40
When might you see: 1. Neutrophilic exocytosis 2. Lymphocytic exocytosis 3. Eosinophilic exocytosis 4. Mast cell exocytosis 5. Erythrocytes?
1. Neutrophils = acute exudative reactions 2. Eosinophils = ectoparasites, allergy 3. Lymphocytes = Seborrhea, Malassezia, atopy, ectoparasitism, immune-mediated (SLE), CTCL 4. Mast cells = allergy, cats 5. Erythrocytes = artifcat, coagulation, trauma
41
Do keratinocytes play a role in the process of exocytosis?
YES! Keratinocytes produce IL-1 constitutively. When a keratinocyte is damaged, IL-1 will be released. Other cytokines will be released - IL-6, IL-8 - and growth factors - GM-CSF. Inflammatory cells will be called toward the keratinocytes (exocytosis) by these chemical mediators.
42
List five causes of depigmentation
1. VKH 2. CETL 3. Contact irritant dermatitis 4. Leishmania 5. Dermatophytes (Microsporum persicolor)
43
What is a rule out for multinucleate giant cell exocytosis?
Drug reaction
44
List three causes of full-thickness coagulative epidermal necrosis
1. Physical damage-burns, freezing 2. Ischemia (vasculitits vs thromboembolism) 3. Immune (EM, TEN)
45
A histologic pattern is most apparent at ___ magnification.
low
46
Pemphigus foliaceous's target
Desmoglein-1
47
The most common autoimmune disease classified as a vesicular and bullous disease
Pemphigus foliaceous
48
What skin disease is most commonly associated with acantholysis?
Pemphigus foliaceous
49
crossover syndrome of Pemphigus foliaceous and Discoid Lupus Erythematosus.
Pemphigus Erythematosus
50
Pemphigus vulgaris targets
Desmoglein-3 (very rare and severe vesicobullous and ulcerative AI ds)
51
2nd most common AI ds classified in interface ds of the dermal-epidermal jxn.
Discoid Lupus Erythematosus
52
Discoid Lupus Erythematosus lesions are restricted to \_\_\_.
the face (nasal planum spec) (skin sloughing off)
53
A necrotizing skin ds where cytotoxic T cells attack keratinocytes causing apoptosis.
Erythema multiforme (EM)
54
What causes Malazzezia dermatitis?
Mallasezia pachydermatisis (Korean snowmen); lichenification (skin thickening)
55
What is the most common type of hypersensitivity dermatitis in cats and dogs?
flea bite hs
56
What is the most common cause of panniculitis?
trauma
57
What is the most common malignant skin tumor in dogs?
mast cell tumor (is benign in cat)
58
what is the general rule when it comes to melanocytoma?
haired skin: benign; mucocutaneous jxns & hairless mucosa-malignant
59
what is the 3 most common locations of malignant melanoma?
oral cavity, lip, nailbed
60
what is the ddx for malignant melanoma?
subungal squamous cell carcinoma, keratoacanthoma
61
Anal sac gland carcinoma involves what type of gland?
apocrine
62
Is anal sac gland carcinoma common in dog or cat?
no neither; female is more common though
63
what is the importance of anal sac gland carcinoma?
causes hypercalcemia
64
what is the ddx for anal sac gland carcinoma?
hepatoid (perianal) gland tumor
65
What are the 3 most common locations for a HSA?
spleen, heart, skin
66
malignant tumor of vascular endothelium
HSA
67
what type of HSA is more aggressive?
intradermal
68
name 3 bovine papilloma virus induced skin tumors
papillomas in cattle, fibromas in deer, sarcorids in horse (#1 malignant skin tumor in horse \<4yo)
69
what breed is associated with acquired pattern alopecia?
Dachshunds
70
where do males get acquired pattern alopecia?
pinnae
71
where do females get acquired pattern alopecia?
skin cd to pinnae, chest, ab, cd thighs
72
what are the ddx for acquired pattern alopecia?
endocrinopathies, canine ear margin seborrhea
73
when does cyclical (seasonal) flank alopecia occur?
late fall to early spring (hair grows back late spring)
74
Witch's feet is the common histo pattern to this alopecia ds.
cyclical (seasonal) flank alopecia
75
what is the most common endocrinologic skin ds in dogs?
hypothyroidism
76
where does alopecia occur in hypothyroidism?
frictional areas (get scales)
77
myedema (droopy face) is common in this alopecia ds
hypothyroidism
78
Alopecia X occurs in what kind/breed of dogs? where?
plush coated dogs in the frictional areas
79
This alopecia ds causes decrease elasticity and thinning of the skin, along with comedones (blackheads)
hyperglucorticioidsm (Cushing's)
80
aggressive fibrosarcoma w/ high mortality in cats seen at vaccination sites
Vaccine- associated fibrosarcoma
81
Are vaccine-assoc fibrosarcomas highly recurrent?
yes
82
Squaomous cell carcinomas occur in what kind of animals?
white (sun-damaged skin) (cats-related to FIV possiblity, whitefaced cows, etc)
83
What grade of mast cell tumor is most common?
Grade 2- possible metastasis & recurrence w 3 yr survival rate of 55%.
84
What is the best organ to biopsy for a mast cell tumor determination?
regional ln
85
what is the most common non-neoplastic mass?
fibroadnexal hamartoma
86
CD3+ is a ____ cell marker
T
87
CD79a- is a ___ cell marker
B
88
Cutaneous LSA are of __ cell origin
T cell (look for CD3+)
89
malignant tumor of melanocytes
malignant melanoma
90
benign tumor of melanocytes
melanocytoma
91
most common tumor in young dogs and unique to dogs
cutaneous histocytoma (solitary button tumor, spont regresses)
92
common benign tumor of fat
lipoma
93
What sex of dog is more likely to have a hepatoid (perianal) gland adenoma and how do you fix it?
intact male--\>recommend castration
94
Uv light can induce this kind of tumor in white animals
squamous cell carcinoma (external nares, pinnae, eyelids)
95
the largest organ in the body
skin
96
growing stage of hair
anagen
97
transitional phase of hair (short)
catagen
98
resting stage of hair (hair is really thin)
telogen
99
old hair is shedding (phase)
exogen
100
"French flat" or patriotic ds (red white blue histo) is common for what epidermis ds? and what is the ddx?
superficial necrolytic dermatitis (ddx: distemper virus-thick crusty footpads)
101
What are Splendore-Hoeppli bodies?
Reaction pattern where eosinophils encircle something (collagen, hyphae, etc.)
102
What are hyphal "ghosts"?
clear spaces representing poorly stained hyphae

Histopathology (6 decks)

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