Dermatopathology Flashcards
(32 cards)
skin is composed of what layers? what is underneath?
- epidermis
- dermis
> contains adnexa >eg. hair follicles, glands
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- subcutaneous striated muscle is under that
Histology of Epidermis
- Cells of the epidermis are:
> types?
> what is cornification? purpose
- thickness / barrier?
- shape?
- Cells of the epidermis are keratinocytes
> Basal, spinous, granular, squamous (corneocytes) types
> Cornification is a unique form of cell death - Very thin viable cell layer. Cornified layer is the main barrier.
- Normal undulation and corrugation
Epidermis - keratinocytes - layers and components in them
Cornified cell layer (Stratum corneum)
◼ Squamous keratinocytes = corneocytes
◼ Basket weave keratin
◼ Compact keratin
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Granular layer (Stratum granulosum)
◼ Granular keratinocytes with keratohyaline
granules
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Prickle cell layer (Stratum spinosum)
◼ Spinosal keratinocytes with desmosomes
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Basal layer (Stratum basale)
◼ Basal cells (keratinocytes) with hemidesmosomes anchoring them to dermis
◼ Basement membrane
EPIDERMIS: Stratum Corneum; histology
◼ 20 overlying corneocytes in this layer.
◼ Histologically we recognise
> Basket weave layer
> Compact keratin layer
> Nucleated cells
◼ Lipid between corneocytes forms the mortar between the bricks of corneocytes = barrier function
EPIDERMIS: Stratum Corneum; structure, properties, functions
◼ Formed by corneocytes (bricks) and the “continuous lipid layer” (mortar)
◼ has a barrier function which is critical
◼ is hydrophobic
◼ is responsible for innate immunity
◼ desquamates
EPIDERMIS: Stratum Corneum; Response to injury
Hyperkeratosis = increase in thickness of stratum corneum
◼ Increased ‘basket weave’
> Basket weave [orthokeratotic] hyperkeratosis
◼ Increased compact keratin
> Compact [orthokeratotic] hyperkeratosis
◼ Increased nucleated corneocytes
> Parakeratotic hyperkeratosis = parakeratosis
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Lipid loss
◼ Reduced protective lipid barrier
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Desquamation
EPIDERMIS: Response to injury – epidermal hyperplasia
> what exactly happens?
◼ Epidermis is labile
◼ Basal layer is made of adult stem
cells
◼ Epidermis responds to injury by HYPERPLASIA
> Hyperkeratosis
> Hypergranulosis
> Acanthosis
> Basal cell hyperplasia
> Larger rete ridges
ADNEXA of haired skin
◼ Hair follicle
> produces hair
◼ Sebaceous gland
> Produces sebum
> Contributes to lipid barrier
◼ Apocrine sweat gland
◼ Arrector pili muscle
Hair follicle - structural components
Infundibulum
◼ Same as epidermis
◼ Ostium to sebaceous duct
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Isthmus
◼ sebaceous duct to the arrector pili muscle attachment
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Inferior portion
◼ Below the arrector pili muscle
◼ Bulb and dermal papilla
dermis - components
◼ Connective tissue – collagen and elastin
> Superficial dermis
> Middle dermis
> Deep dermis
◼ Blood vessels
◼ Nerves
◼ Lymphatics
DERMATOPATHOLOGY - masses and non masses
> what types are there?
Masses
◼ Non neoplastic masses
◼ Neoplasms
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No Masses
◼ Noninflammatory skin diseases
> Tissue based approach (keratin, collagen, follicle cycle)
◼ Inflammatory skin disease
> Pattern analysis – recognition system of dermatopathology (pathogenesis)
Skin ‘masses’:
1. Non-neoplastic lesions
- Types, definitions, properties
I. Cysts
◼ Definition: Cavities lined by epithelium
◼ Derived from
> Epidermis – epidermal cyst
> Adnexa
=> Hair follicles – follicular cyst
=> Glands – sebaceous cyst, apocrine cyst
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II. Hamartomas
◼ Definition: Excessive normal tissue in a location where it is normally found.
◼ Most are fibroadnexal (dermis and adnexal combinations) or collagenous
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III. Miscellaneous
follicular cysts, types
◼ Infundibular
◼ Isthmus
◼ Panfollicular
Glandular cysts, types
◼ Sebaceous duct cyst
◼ Sweat glands
> Apocrine cysts
> Eccrine cysts
Neoplasia;
Basic Nomenclature
prognosis?
◼ Epithelial
◼ Mesenchymal (stromal)
◼ Round cell
◼ Other
> Neuroectodermal – melanocytic tumors, Merkel cell tumor
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◼ Phenotype = prognosis
Epithelial neoplasms of skin
- malignant or benign?
Most are benign
Neoplasms of Skin; Epithelial neoplasms
- what tissues can be affected?
◼ Epidermis
◼ Adnexa
> Follicles
> Glands
> Horns
> Claw/hoof - Nailbed tumors
Epithelial neoplasms; epidermal - types
Spinous Keratinocyte
◼ Acanthoma
◼ Squamous cell carcinoma in situ
◼ Squamous cell carcinoma (SCC)
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Basal keratinocyte
◼ Basal cell tumor
◼ Basal cell carcinoma
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Combination
◼ Papilloma
◼ Basosquamous tumor
◼ Basosquamous carcinoma
Epithelial neoplasms; nomenclature
◼ Tricho- or pilo-
◼ Kerato-
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◼ -oma
◼ -blastoma
Prefix
◼ Tricho- or pilo- for hair
◼ Kerato- for keratin producing
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‘Suffix’
◼ Tumor or -oma
◼ Adenoma, adenocarcinoma
◼ Papilloma, epithelioma, acanthoma, carcinoma
◼ -blastoma – adult stem cell tumor
Epithelial neoplasms - Follicular
- infundubulum, isthmus, inferior, combo
◼ Infundibulum (superficial)
> Infundibular keratinizing acanthoma (previously called keratoacanthoma)
◼ Isthmus (middle) and inferior
> Tricholemmoma (benign tumour originating from the outer root sheath of the hair follicle)
◼ Inferior (deep) follicle (including bulb)
> Pilomatrixoma
> Trichoblastoma
◼ Combinations of follicular components
> Trichoepithelioma
Epithelial neoplasms; Glands - what types do we see?
> sebaceous glands and sweat glands…
Sebaceous glands
◼ Adenoma
◼ Epithelioma
◼ Carcinoma
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Sweat glands
◼ Apocrine glands (throughout epidermis for furred animals)
> Adenoma
> Carcinoma
◼ Eccrine glands (only paw pads)
> Adenoma
> Carcinoma
Neoplasms of skin:
Mesenchymal neoplasms
- general properties
- Invasive
- Rarely metastasise
Neoplasms of skin:
Mesenchymal neoplasms - what types of tissues
- terminology
◼ Dermal and SC connective tissue (fibro-, myxo-)
◼ Vessels (endothelial and perivascular tumors)
◼ Nerve (nerve sheath tumor)
◼ Arrector pili muscle (leiomyo-)
◼ Skeletal muscle (rhabdomyo-)
◼ Adipose tissue (lipo-)
Canine soft tissue tumors
- how common?
- characteristics / diagnostics / ddx
◼ Very common
◼ Approach to this group of tumors is changing/has changed.
◼ Generic term (group diagnosis) representing different cell types
> Phenotypic similarity – spindle cell tumor of mesenchymal tissue type
=> Most are perivascular wall tumours (pericytes are around capillaries)
> Different subtypes with behavioural similarity
◼ Not a specific diagnosis. Aim for specific diagnosis and use the latest information on prognosis.
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◼ DDx lipoma, seroma
