HistoPath - Skin Flashcards
What are the layers of the skin
Epidermis, dermis, SC fat
Epidermis:
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum
- Stratum basale
Dermis
Subcutaneous fat
What is within the dermis layer of the skin
Blood vessels
Sweat glands
Hair follicles
Sebaceous glands
Nerve fibres
How long does it take for skin cells to complete their life cycle
28-40 days
Describe the following inflammatory reaction patterns: spongiotic, lichenoid, vesiculobullous, psoriasiform, granulomatous, vasculaopathic
Spongiotic: intraepidermal intercellular OEDEMA
Lichenoid: basal cell damage, interface dermatitis
Psoriasiform: epidermal HYPERPLASIA
Vesiculobullous: blistering within or beneath the epidermis
Granulomatous: granulomas e.g. TB, sarcoid
Vasculaopathic: pathological changes in cutaneous blood vessels
Give an example of spongiotic inflammatory skin disease
Eczema - intra-epidermal intercellular oedema
Give an examples of lichenoid inflammation
Lichen planus
Eyrthema multiforme
toxic epidermal necrolysis (TEN)
Stevens-Johnson syndrome (SJS)
What is the pathophysiology of lichen planus and how does it present
T-cell mediated destruction of bottom keratinocytes → band-like inflammation
Cannot distinguish between dermis and epidermis
Presents with purple/red papules + plaques on the wrists and arms
White lines in the mouth (Wickham striae)
What is the pathophysiology of plaque psoriasis
Psoriasiform inflammation of the skin on the extensor surfaces
Silver/white plaques
Rapid keratinocyte turnover time (7 days) → thickened epidermis → layer of parakeratosis on the top → Psoriasiform hyperplasia
The stratum granulosum disappears as there is not enough time to form it → dilated vessels
Munro’s microabscesses (recruitment of neutrophils)
What are vesiculobullous reactions and give examples
Autoimmune - Abs against the epidermis
Bullous pemphigoid
Pemphigus vulgaris
Pemphigus foliaceus
How does bullous pemphigoid present and how is it diagnosed
Elderly
Tense bullae (dermo-epidermal junction)
- Flexor surfaces
- May be precipitated by PD-1 and DPP4 inhibitors
Diagnosis is via immunofluorescence → Detects IgG anti-hemidesmosome
What is the pathophysiology of bullous pemphigoid
Auto-immune: IgG and C3 attack the hemidesmosomes of the epidermal basement membrane → SUB-epidermal bullae (Deep)
Eosinophils are recruited → releases elastase → damages anchoring proteins → fluid fills the gap between BM and epithelium
How does pemphigus vulgaris present and how is it diagnosed
Flaccid blisters (mucous membranes)
- Ruptures easily
- Skin and mucosal membranes
Immunofluorescence → chicken-wire pattern (IgG surrounding)
What is the pathophysiology of pemphigus vulgaris
IgG attacks desmosomes between the keratin layers (acantholysis) → loss of intracellular connections
T2 HS reaction
Superficial bullae
Describe pemphigus foliaceus (presentations, pathophysiology, diagnosis)
SUPERFICIAL
Top layer is very thin so never blisters
IgG-mediated to desmoglein 1 – outer layer of stratum corneum shears off
Diagnose with immunofluorescence
What is the histology for eczema
Acute: spongiosis (oedema between keratinocytes), inflammatory infiltrate in dermis, dilated dermal capillaries
Chronic: acanthosis, hyperparakeratosis, lichenification, crusting, scaling, T cells, eosinophils
What are the clinical signs of psoriasis
Auspitz’ sign: rubbing the skin causes pin-point bleeding
Koebner phenomenon: lesions form at the site of trauma
What is the difference between rosacea and pityrasis rosea
Rosacea = redness, pimples, swelling, VD treated, remits spontaneously- emollients, uv-b/ acyclovir, 10-35 year olds, hhv6/7
Pityrasis rosea = herald patch, eruption smaller , older children + young adults
Describe basal cell carcinomas appearance and histology
Benign
Rolled, pearly-edge, central ulcer, telangiectasia
“Rodent ulcer” as it burrows away
Occurs in sun-exposed areas
Histo: dysplastic change, PCTH mutation, bottom keratinocytes affected, cannot invade BM (cannot met)
What is the pre-malignant stage of melanoma called
Bowen’s disease (becomes malignant when it invades the BM)
Squamous cell carcinoma in situ
Keratinocytes become more pleiomorphic and larger with mitotic figures
Describe squamous cell carcinomas and its histology
Poorly to well differentiated
Poorly = cannot determine original cell lineage
Per-neural invasion may occur
Histo: Pleomorphic squamous epithelial cells arising from the epidermis and extending into the dermis
What are the types of benign naevus
Junctional: melanocytes nest in the epidermis, flat and coloured
Compound: nests in the epidermis and dermis, raised area, surrounding by flat pigmented area
Intradermal: nests in the dermis, raised area, skin coloured or pigmented
What are the characteristics of a malignant melanoma lesion
ABCDE – Asymmetry, Border, Colour, Diameter, Evolution
Asymmetrical
Irregular border
Variable pigmentation
Bleeding
Size >4mm
Itchy
Growing
What is the histology of malignant melanoma
Pagetoid spread - junctional melanocytes move up through the dermis (vertical growth) instead of maturing and dropping out the dermis
Atypical Melanocytes - mitotic figures
Spreads to lymph nodes > blood
How is malignant melanoma staged
“Breslow Thickness”, along with ulceration, lymphovascular invasion, perineural invasion, Clark level, Microsatellites, TILs, Regression, Mitotic index
What are the subtypes of malignant melanoma
Lentigo maligna melanoma: occurs on sun exposed areas of elderly Caucasians, flat, slowly growing black lesion
Superficial spreading malignant melanoma: irregular borders with variation in colour
Nodular malignant melanoma: can occur on all sites, more common in the younger age group.
Acral Lentiginous melanoma: occurs on the palms, soles, and subungual areas
Describe seborrheic keratosis and its histopathology
“Cauliflower”, pigmented, gets caught on clothing (and taken off)
Stuck-on appearance, harmless and benign
Lots of growth and ordered proliferation
Ordered and benign growth
“Horn cysts” – epidermis entrapping keratin
Describe sebaceous cysts
Transluminates, central punctum, circumscribed, hot
Squamous cell lining surrounding the cyst
