Dermatopathology Flashcards
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
