skin Flashcards
Patho of Urticaria
Immediate (type 1) hypersensitivity reaction -> corss-linkage of IgE on mast cells which cause degranualtion
Microscopic Findings:
* Superficial perivenular infiltrate of mononuclear cells (Lymphatic vessel dilatation)
* Superficial dermal oedema, creating more widely spaced collagen bundles
* Degranulation of mast cells,
features of?
Urticaria
Degranulation of mast cells in Urticaria can highlighted using ——– stain
Giemsa stain
CP of Urticaria
Erythematous, oedematous, and Pruritic wheals(form after the degranulation of mast cells)
cause of Allergic Contact Dermatitis
Type IV hypersensitivity reaction secondary to contact allergens (e.g, poison ivy, nickel)
CP of allergic contact dermatitis
localized pruritic (itchy) skin lesions, blisters w/ clear fluid
* bullae: blisters w/ clear fluid
Microscopic Findings:
* Spongiosis (epidermal odema)
* Intercellular bridges are stretched
* Superficial perivascular lymphocytic infiltrate
* Oedema of dermal papillae
* Mast cell degranulation
features of?
Allergic Contact Dermatitis
*note very similar micro features of Urticaria
CP of Erythema Multiforme
Target- like papules
(consisting of red macules or papules with pale vesicular or eroded centers)
**
Macroscopic features:
* pathces have pale, vesicular, or eroded centers (Target-like papules)
Microscopic Findings:
* Dermal oedema
* lesions w/ degenerating (apoptotic) keratinocytes w/ lymphocytic infiltrates
Erythema Multiforme
*keratinocytes: the major cell type of the epidermis
CP of Psoriasis
pink to salmon-coloured palques w/ silvery scaling
Microscopic Findings:
* Epidermal thickening (acanthosis), w/ parakeratotic (nuclei still in stratum corneum)
* loss of the stratum granulosum and parakeratotic scale (due to lack of maturation)
* Regular elongation of the rete ridges
* Thinning of the epidermal cell layer overlying the tips of dermal papillae
Features of?
Psoriasis
patho of Linchen PLanus
* chronic inflammatory skin disorder
CD8+ T cell-mediated cytotoxic immune response against antigens in the basal cell layer and the dermo-epidermal junction
**
CP of Lichen Planus
6 P’s
1) Pruritic, purple, polygonal, planar papules, and plaques of skin and squamous mucosa
2) Mucosal involvement –> Wickham striae
**
Microscopic Findings:
* The lymphocytes are intimately associated with basal keratinocytes, which often atrophy or become necrotic
* “zig-zag” contour/”saw-tooth” infiltrate of lymphocytes at Dermo-epidermal interface (junction)
* Presence of anucleate, necrotic basal cells (colloid bodies or Civatte bodies)
features of?
Lichen Planus
cause of Lichen simplex Chronicus
Response to local repetitive trauma, such as continual rubbing or scratching
CP of Lichen Simplex Chronicus
Raised, erythematous, and scaly lesions
Microscopic Findings:
* Acanthosis (epi thickening)
* Hyperkeratosis
* Hypergranulosis ( ↑ thickness of the stratum granulosum)
* Solar elastosis
* Elongation of the rete ridges
* Fibrosis of the papillary dermis
* Dermal chronic inflammatory infiltrate
features of?
Linchen Simplex Chronicus
cause of Impetigo
* superficial bacterial infection
Staphylococcus aureus, Streptococcus pyogenes
CP of Impetigo
lesions w/ Honey-coloured crusting
Microscopic Findings:
* Accumulation of neutrophils beneath the stratum corneum that often produces a sub-corneal pustule
* Superficial dermal inflammation accompany these findings
* Bacterial cocci in the superficial epidermis (demonstrated by Gram stain)
features of?
impetigo
obv+ skin condition
Skin condition: Superficial dermal fungal infection caused by Candida albicans
Obv: Satelite lesions
Microscopic Findings:
*Neutrophilic infiltrate in the epidermis
*Psoriasiform hyperplasia
Candidiasis of the Skin
Psoriasiform hyperplasia-> Candida
Stain used for Candida causing superfical Dermal fungal infection
PAS
Obv+ skin disorder
Condition: Deep dermal fungal infection caused by Apergillus
Obv: A- Erythematous subcutaneous nodule
B- Focally haemorrhagic lesion
Histochemistry for Deep Dermal fungal infection caused by Aspergillus
1) PAS- Periodic Acid-Schiff
2) Gomori methenamine silver stains
*identify fungal organisms
cause of Verrucae (Warts)
* viral infection
Human Papilloma Virus (HPV)
Microscopic Findings:
* Epidermal hyperplasia
* Cytoplasmic vacuolisation [koilocytosis] (preferentially of the more superficial epidermal layers) –> Halos of pallor surrounding infected nuclei
* Infected cells with prominent kerato-hyalin granules and jagged eosinophilic intracytoplasmic protein aggregates (result of impaired maturation)
features of?
Verrucae (Warts)
the 4 types of Verrucae (Wrats)
- Verruca Vulgaris
- Verruca Plana (Flat Wart)
- Verruca Plantaris/Palmaris
- Condyloma Acuminatum (Venereal Wart)
most common type of Verrucae (Wrats)
Verruca Vulgaris
loc of Verruca Vulgaris
dorsum of the hand
Verucca Vulgaris presents w/ Rough, ————–to ————— skin coloured papule/plaque Macroscopically
hyperkeratotic to papillomatous
Hyperkeratotic –> thickening of the outer layer of the skin
Macroscopic features:
- Rough, hyperkeratotic to papillomatous skin coloured papule/plaque
microscopic features :
- Papillomatous hyperplasia
- Prominent granular layer
- Inward bending of rete
- Koilocytosis
features of ?
Veruuca Vulgaris
**
what type of Verruca (Wrats) has the following microscopic features:
- Multiple “bird’s eye” nuclei in the granular cell layer
Verruca Plana
Macroscopic features:
- Warty cauliflower-like lesion w/ papillary or polypoid fronds
Microscopic features :
- Papillomatous mammillated epithelial hyperplasia
- Koilocytic changes
- Hyperkeratosis
features of?
Condyloma Acuminatum (Venereal Wart)
patho of Pemphigus
- Antibody-mediated (type II) hypersensitivity reactions
- IgG auto-antibodies that bind to intercellular desmosomal proteins (Desmoglein types 1 and 3) of skin and mucous membranes
Microscopic Findings:
* Acantholysis: Lysis of the intercellular adhesive junctions between neighbouring squamous epithelial cells that results in the rounding up of detached cells
* Superficial dermal infiltrates comprised of lymphocytes, macrophages, and eosinophils
features of?
Pemphigus
Direct Immuno-Fluorescence of Pemphigus
Fishnet-like pattern of intercellular IgG deposits
- Acantholysis selectively involves the layer of cells immediately above the basal cell layer, giving rise to a supra-basal acantholytic blister
what type of Pemphigus is this?
Pemphigus Vulgaris
**
microscopic features;
- Acantholysis in the granular cell layer with “missing” stratum corneum
- Neutrophils in the granular cell layer
- Separation of the corneum from the rest of the epidermis
features of?
Pemphigus Foliaceus
Microscopic Findings:
* Perivascular infiltrate of lymphocytes and variable numbers of eosinophils, occasional neutrophils
* Superficial dermal oedema
* Associated basal cell layer vacuolisation; The vacuolated basal cell layer eventually gives rise to a fluid-filled sub-epidermal non-acantholytic blister
features of?
Bullous Pemphigoid
Direct Immuno-Fluorescence of Bullous Pemphigoid
Linear deposition of IgG antibodies and complement in the epidermal basement membrane
Epi of Dermatitis Herpetiformis
- Males
- 80% occurs is ass. w/ Coeliac disease
patho of Dermatiis Herpetiformis
Genetically predisposed persons develop:
* IgA antibodies to dietary Gluten (derived from the wheat protein Gliadin) and
*IgA auto-antibodies that cross-react with epidermal transglutaminase , expressed by keratinocytes
**
CP of Dermatitis Herpetiformis
Pruritic urticaria and grouped vesicles
**
Microscopic Findings:
* Neutrophils accumulate selectively at the tips of dermal papillae, forming small micro-abscesses- “Papillary Abscess”
* The basal cells overlying these micro-abscesses show vacuolisation and focal dermo-epidermal separation that ultimately coalesce to form subepidermal blisters
features of?
Dermatitis Herpetiformis
**
CF of Seborrhoeic Keratosis
- Round, exophytic, coin-like plaques
- “Stuck-on” appearance
- Tan to dark brown colour
**
Microscopic Findings:
* Monotonous sheets of small cells that resemble the basal cells of the normal epidermis
* Variable melanin pigmentation is present within these basaloid cells
* Hyperkeratosis at the surface
* Presence of small keratin-filled cysts (Horn cysts)
* Down-growth of keratin into the main tumour mass (Pseudo-Horn cysts)
features of?
Seborrhoeic Keratosis
Patho of Acitinic Keratosis
TP53 mutations caused by UV light-induced DNA damage
**
Clinical presentation of Acitinic Keratosis
Small (<1cm), Rough, erythmatous(red) or brownish papules
- rough –> sandpaper- like on touch
**
Macro features:
- red, scaly lesions w/ rough texture
Microscopic findings:
* Cytologic atypia in the lower portions of the epidermis
* Accompanying hyperplasia of basal cells or atrophy and diffuse thinning of the epidermal surface
* Thickened, blue-gray elastic fibers in the dermis (dermal solar elastosis)
* Thickened stratum corneum, with retained nuclei (parakeratosis)
features of?
Actinic Keratosis
* rough texture –> sand paper like
Acitinic Keratosis is asso. w/ an increased risk of developing?
SCC- Squamous Cell Carcinoma
Risk factors of SCC?
- Chronic exposure to sunlight (e.g. Acitinic Keratosis)
- Industrial carcinogens (tars and oils)
- Chronic ulcers
- Old burn scars
- Ingestion of arsenicals
- Ionising radiation
Patho of SCC
- TP53 mutations caused by UV light-induced DNA damage
- Mutations in HRAS
- Loss-of-function mutations in Notch receptors,
Clinical presentation of SCC in situ
Sharply defined, red, scaling plaques
Clinical presentation of invasive SCC
Nodular, with variable scale and ulceration
**
What skin cancer presents w/ Keratin pearls on Histology?
Squamous Cell Carcinoma (Well-diffrentaited form)
Epi of Basal Cell Carcinoma
Older people
Microscopic Findings:
* Tumour cells resemble the normal epidermal basal cell layer
* Palisading (aligned) nuclei
* Separation of the peripheral border from the stroma (reduced stroma), with a creation of a characteristic cleft
features of?
Basal Cell Carcinoma
Patho of Melanocytic Naevus
Activating mutation in BRAF
Clinical presentation of Melanocytic Naevus
- Small papules; Size: ≤5 mm
- Tan-to-brown, uniformly pigmented
- Well-defined, rounded borders
the 3 types of Melanocytic Naevus
1) Compound
2) Junctional
3) intradermal naevus
What is the diffrence (Microscopically) btw Compound and Junctional Melanocytic Naevus ?
Junctional –> Nest of Mealnocytes grow along the dermo-epidermal junctions
Compound –> Melanocytes grow within the Dermis only
how do junctional / compound Melanocytic Naevus look like?
Compound–> well-defined, Brown nodule w/ rounded borders
Junctional –> Flat uniform bronw macule
Microscopic Findings:
* Junctional component
* Stromal component
* Nevomelanocytes extend into the reticular dermis
* Patterns of dermal involvement: i. Diffuse, ii. Interstitial or iii. Perivascular
* Commonly, adnexal involvement
* Possible involvement of nerves
features of?
Congenital Naevus
patho of Dysplastic naevus
Activating mutation in BRAF
**
CP of Dysplastic naevus
- Larger than acquired naevi (>5 mm)
- Numerous (in Familial Dysplastic Naevus Syndrome)
- Flat macules to slightly raised plaques, with a “pebbly” surface
- variable pigmentation (variegation) * Irregular borders
Macroscopic features:
- Uneven colour with dark brown centers and lighter, uneven edges
- Large and irregular in shape
Microscopic features:
- irregular nuclear contours & hyperchromasia
- Nevus cell nests within the epidermis may be enlarged and exhibit abnormal fusion or coalescence with adjacent nests (bridging)
- Melanin pigment that is phago- cytosed by dermal macrophages
- Subepidermal lamellar sclerosis (‘lamellar fibroplasia’)
features of?
Dysplastic Naevus
patho of melanoma
- Somatic activating mutations in the proto-oncogenes BRAF or NRAS
- Activating mutations in the c-KIT receptor tyrosine kinase
who is at most risk of Melanoma
Fair-skinned individuals
Clincial presentaitons of melanoma
- Rapid enlargement of a pre-existing naevus
- Itching or pain
- Development of a new pigmented lesion, during adult life
- Irregularity of the borders of a pigmented lesion
- Variegation of colour within a pigmented lesion
**
THE ABCDE of melanoma
the 4 types of melanoma
1) Superficial spreading melanoma
2) Lentigo maligna
3) Nodular melanoma
4) Acral melanoma
**
Microscopic Findings:
* Malignant cells grow as poorly formed nests or as individual cells at all levels of the epidermis (pagetoid spread) and in expansile dermal nodules (radial and vertical growth phases)
* large nuclei with irregular contours
* Chromatin is characteristically clumped at the periphery of the nuclear membrane
* Prominent “cherry red” eosinophilic
nucleoli
features of?
Melanoma
**
tumour marker used to detect melanoma
1) S-100
2) MART-2/ Melan-A
3) HMB45
4) AE1/AE3
5) Vimentin
**
Prognosis of Melanoma
Depth of tumor (Breslow thickness) correlates w/ risk of metastasis
