VETM*4490: Derm Path

3 general components of 'skin'

• epidermis

• dermis

• adnexa

cells of the epidermis = ...?

keratinocytes

(basal, spinous, granular, squamous types)

type of keratinocytes in the stratum corneum

squamous (corneocytes)

type of keratinocytes in the stratum granulosum

granular

type of keratinocytes in the stratum spinosum

spinous

type of keratinocytes in the stratum basale

basal cells

structures that hold spinosal keratinocytes in the stratum spinosum together

desmosomes

structures that anchor basal cells in the stratum basale to the dermis

hemisdesmosomes

"desmo-" in desmosome means...?

ligament

difference between cornification vs. keratinization

same thing

granular keratinocytes in the stratum granulosum have ____________ granules

keratohyaline

general term for thickening of the stratum corneum

hyperkeratosis

what are the 3 histologically recognized layers of the stratum corneum

• basket weave layer

• compact keratin layer

• nucleated cells

significance of finding basket weave hyperkeratosis on histology

means it was stimulated to thicken but no trauma (wasn't scratched off)

significance of finding compact hyperkeratosis on histology

means the basket weave layer was either removed or did not develop (most commonly scratching b/c pruritis)

term for incr. nucleated corneocytes in the stratum corneum

parakeratosis

(a.k.a. parakeratotic hyperkeratosis)

where does the arrector pili muscle insert on the hair follicle

isthmus; deeper than the sebaceous gland

the stratum corneum is generally how many cell layers

20

general response of epidermis to injury

hyperplasia

term for hyperplasia of the stratum granulosum

hypergranulosis

term for hyperplasia of the stratum spinosum

acanthosis

term for hyperplasia of the stratum basale

basal cell hyperplasia

product of the sebaceous gland & its function

sebum -> contributes to lipid barrier

the isthmus of a hair follicle extends from __________ to __________ histologically

sebaceous gland to arrector pili muscle attachment site

components of the dermis

• CT (collagen, elastin)

• blood vessels

• nerves

• lymphatics

non-neoplastic skin masses

• cysts

• hamartomas

• misc

definition of a cyst

cavity lined by epithelium

definition of a hamartoma

excessive normal tissue in a location where it is normally found (usually fibroadnexal)

types of cysts

• follicular (infundibular, isthmus, panfollicular)

• glandular (sebaceous duct, sweat glands)

epidermal neoplasms that can arise from spinous keratinocytes

• acanthoma

• squamous cell carcinoma in situ

• squamous cell carcinoma (SCC)

epithelial neoplasms that can arise from basal keratinocytes

• basal cell tumour

• basal cell carcinoma

the prefix "acantho-" means...?

spiny

epithelial neoplasms that arise from a combination of epidermal cell types

• papilloma

• basosquamous tumour

• basosquamous carcinoma

the prefix "kerato-" means...?

keratin-producing

the suffix "-blastoma" means...?

adult stem cell tumour

how common are trichoepitheliomas? Are they benign or malignant?

very common, benign

list 3 general tumour types of the sebaceous gland

• adenoma

• epithelioma

• carcinoma

list 2 general tumour types of sweat glands

• adenoma

• carcinoma

prefixes that refer to the dermis & subcutaneous CT?

fibro-

myxo-

the prefix "rhabdomyo-" refers to...?

skeletal muscle

mesenchymal (stromal) tumours of skin are usually:

a) benign

b) infiltrative w/o metastasizing

c) infiltrative w/ mets

d) highly variable

a) benign

b) infiltrative w/o metastasizing

c) infiltrative w/ mets

d) highly variable

round cell tumours [5]

• histiocytic

• mast cell tumour

• plasmacytoma

• lymphoma

• TVT

the _____________ are referred to as "hepatoid glands"

perianal

3 general tumour types of perianal glands

• adenoma

• epithelioma

• carcinoma

is the metastatic rate of apocrine adenocarcinomas of the apocrine gland of the anal sac high or low

high

differentials for nailbed mass

• inclusion cyst

• keratoacanthoma

• SCC

• osteosarcoma

• malignant melanoma

how many biopsies should you take when doing skin biopsies

6 = good

3 = minimum

(taken from multiple sites from a range of lesions)

how to prep a skin site for biopsy

• don't surgically prep the biopsy site

• include scale and crust

• don't clip the hair completely off (they section along the hair)

instruments to use for skin biopsy

1. Baker skin punch:

6mm usually

3mm for delicate sites

2. Scalpel -> wedge/ excisional biopsy for large lesions

where to take skin biopsies for the following lesions:

a) pruritis or scales

b) crusts

c) nodules

d) ulceration

e) alopecia

a) pruritis or scales: range of affected areas

b) crusts: pustules, vesicles, new lesions, crusts

c) nodules: incisional biospy

d) ulceration: edge of lesion, vesicles

e) alopecia: severe & less severely affected areas

when are derm cases good candidates for biopsy?

• clinical work-up unsuccessful

• clinical features of immune-mediated disease or other diseases where biopsy confirmation is necessary

• no response to apparently appropriate therapy

• anything really unusual or serious (ex. hyphomycosis, pustular demodicosis)

information to include when sending skin biopsies to derm pathologist

• full signalment -breed, age, sex

• history - duration, major clinical issues, previous workup & response, other test results

• description of lesions - correct terminology, distribution, pruritus scale, pictures

• attempted treatments & results - esp. Abx, parasite Tx, steroids

• your DDx - preferably ranked

3 parts of a derm path report

• description of microscopic lesions

• diagnosis

• comment

name of the C fibre nerves that extend into the epidermis and transmit 'itch signals'

intraepidermal nerve fibres (IENF)

how are intraepidermal nerve fibres (IENF) stimulated

• directly (ex. traumatic neuroma, nerve sheath tumour, dry skin, intradermal lymphocytes)

• chemical mediators

• keratinocyte products (cytokines)

how can superficial pyoderma result from pruritus

itchy -> scratch off stratum corneum -> reduced barrier function -> superficial infection

deepest layers of epidermis removed in 'hot spot' (superficial spreading pyoderma)

stratum basale & spinosum

how can pruritus cause alopecia

scratching, chewing, etc. -> hair breakage

examples of chemical mediators that stimulate IENF (-> pruritus)

• insect bite (venom = vasoactive amines - histamine & serotonin)

• mast cell degranulation (d/t scratching, IgE mediated -> type I hypersensitivity)

how can histamine result in:

a) erythema

b) wheals

a) erythema: vasodilation -> hyperemia

b) wheals: incr permeability -> edema

most common & least specific derm pattern

perivascular dermatitis

"acral" refers to...?

peripheral

what are 'actinic' effects

effects from sun rays

how does low humidity result in pruritus

dry skin -> direct stimulation of IENFs

how does epitheliotrophic lymphoma cause pruritus

the neoplasic intraepidermal lymphocytes directly stimulate the IENF

why do insect bites cause pruritus

the venom = vasoactive amines (histamine, serotonin) -> chemical mediators, stimulation of IENF

Medical treatments for pruritus that target chemical mediators

• antihistamines

• corticosteroids

• cyclosporine

• oclacitinib (Apoquel)

• caninized monoclonal Ab against IL-31 (Cytopoint)

histo term for erythema (reddening of skin)

vascular dilation

(often with endothelial hypertrophy)

define hives

a.k.a. wheals

= transient sharply circumscribed raised lesions resulting from dermal edema

histo term for wheal

dermal edema

outcomes/ sequelae of pruritus

• self trauma & reduced barrier function -> scaling, ulceration, alopecia, actinic effects, pyoderma

• perivascular dermatitis (PVD)

histo patterns seen with perivascular dermatitis

epidermis:

• compact hyperkeratosis

• hypergranulosis

• acanthosis

dermis:

• vascular dilation

• edema

• endothelial hypertrophy

cell type expected in perivascular dermatitis (PVD) due to cutaneous adverse food reaction (CAFR; food allergy)?

a) cell-poor

b) eosinophilic

c) neutrophlic

d) lymphocytic

e) histiocytic

a) cell-poor

b) eosinophilic

c) neutrophlic

d) lymphocytic

e) histiocytic

cell type expected in perivascular dermatitis due to xerosis (dry skin)?

a) cell-poor

b) eosinophilic

c) neutrophlic

d) lymphocytic

e) histiocytic

a) cell-poor

b) eosinophilic

c) neutrophlic

d) lymphocytic

e) histiocytic

cell type expected in perivascular dermatitis (PVD) due to leishmania?

a) cell-poor

b) eosinophilic

c) neutrophlic

d) lymphocytic

e) histiocytic

a) cell-poor

b) eosinophilic

c) neutrophlic

d) lymphocytic

e) histiocytic

cell type expected in perivascular dermatitis (PVD) due to superficial pyoderma?

a) cell-poor

b) eosinophilic

c) neutrophlic

d) lymphocytic

e) histiocytic

a) cell-poor

b) eosinophilic

c) neutrophlic

d) lymphocytic

e) histiocytic

cell type expected in perivascular dermatitis (PVD) due to chronic antigenic stimulation ex. chronic pyoderma?

a) cell-poor

b) eosinophilic

c) neutrophlic

d) lymphocytic

e) histiocytic

a) cell-poor

b) eosinophilic

c) neutrophlic

d) lymphocytic-plasmacytic

e) histiocytic

cell type expected in perivascular dermatitis (PVD) due to flea allergy dermatitis (FAD)?

a) cell-poor

b) eosinophilic

c) neutrophlic

d) lymphocytic

e) histiocytic

a) cell-poor

b) eosinophilic

c) neutrophlic

d) lymphocytic

e) histiocytic

cell type expected in perivascular dermatitis (PVD) due to canine atopic dermatitis (CAD)?

a) cell-poor

b) eosinophilic

c) neutrophlic

d) lymphocytic

e) histiocytic

a) cell-poor

b) eosinophilic

c) neutrophlic

d) lymphocytic

e) histiocytic

^could be cell poor or eosinophilic

cell type expected in perivascular dermatitis (PVD) due to canine allergic dermatitis?

a) cell-poor

b) eosinophilic

c) neutrophlic

d) lymphocytic

e) histiocytic

a) cell-poor

b) eosinophilic

c) neutrophlic

d) lymphocytic

e) histiocytic

histo term for scales

• thickened stratum corneum

• hyperkeratosis

• parakeratosis

derm term for an accumulation of loose fragments of keratin (stratum corneum)

scale

a scale is a ____________ (process) defect

cornification

difference between a primary vs. secondary cornification disorder

primary = failure to release corneocytes

secondary = reactive hyperplasia

3 examples of primary cornification disorders (failure to release corneocytes)

• nasodigital hyperkeratosis

• nasal hyperkeratosis of Labs

• ichthyosis

secondary cornification disorders (reactive hyperplasia) occurs d/t...? [3]

basic response of epidermis to injury:

• trauma, scratching

• infection

• altered barrier function

clinical correlate of hyperkeratosis

scaling

term for retention of nuclei in the stratum corneum

parakeratosis

3 causes of parakeratosis

• Zn responsive dermatosis

• vitamin A responsive dermatosis

• superficial necrolytic dermatitis (hepatocutaneous syndrome)

clinical correlate of parakeratosis

scaling

clinical correlate of hypergranulosis (hyperplasia of stratum granulosum)

no clinical correlate

clinical correlate of acanthosis (hyperplasia of stratum spinosum)

no clinical correlate

histological term for a skin plaque

same: plaque

which part of the hair follicle is identical to the epidermis?

infundibulum

histological term for excessive keratin forming in infundibulum of hair follicle

follicular keratosis & follicular parakeratosis

clinical term for excessive keratin forming in infundibulum of hair follicle

follicular casts;

comedones

what are comedones

follicles plugged with keratin (blackheads, whiteheads)

histo term for comedones

follicular dilatation and keratosis

what is a 'crust'

dried inflammatory exudate on surface of skin

ex. dark crust usually = hemorrhagic;

yellow-green crust typical of pyoderma

histo term for crusts

serocellular crust