Histopathology 13: Skin Pathology Flashcards
Baby with itchy yellow scales on his scalp and nappy rash.
Most likely diagnosis ?
Seborrheic dermatitis (cradle cap)
Rain drop plaques seen in children 2 weeks post strep throat infection.
Most likely diagnosis ?
Guttate psoriasis
What type of hypersensitivity reaction is psoriasis ?
Type IV T cell mediated
Koebner phenomenon
Auspitz’s sign
Histology: Parakeratosis, loss of rete ridges and “test tubes in a rack appearance”
Most likely diagnosis ?
Psoriasis
Purple, pruritic, polygonal, papules and plaques with Wickam’s striae
Histology: Hyperkeratosis with sawtoothing of rete ridges
Most likely diagnosis ?
Lichen Planus
Histology: Linear deposition of IgG antibodies bound to hemidesmosomes of the basement membrane
Nikolsky’s sign -ve
Bullous pemphigoid
Histology: Net like pattern of IgG deposits on desmosomal proteins causing intraepidermal bullae
Nikolsky’s sign +ve
Pemphigus
Which premalignant skin lesion is hard to differentiate from SCC and is described as: a dome shaped nodule with a necrotic, crusted centre which spontaneously clears in 2-3 weeks ?
Keratocanthoma
What is the difference between Bowen’s disease and SCC ?
Bowen’s disease is premalignant and does not invade through the basement membrane
Lesion with pearly rolled edges and telangiectase with palisading nuclei on histology.
Most likely diagnosis ?
BCC
List 4 subtypes of malignant melanoma ?
Superficial spreading melanoma
lentigo maligna melanoma
nodular malignant melanoma
Acral lentigous melanoma
Where do you see acral lentigous melanoma ?
Palms and soles
Salmon pink rash, herald patch, christmas tree distribution.
Most likely diagnosis ?
Pityriasis rosea
descibe palmar plantar skin
no sebaceous glands
very thick corneal layer
describe bullous pemphigoid
vesiculobullous
elderly patients
flexor surfaces
tense bullae
10-20% mortality
AI disorder driven by IgG and C3 which attack the basement membrane
recruit eosinophils which release elastase - further damages the anchoring proteins that are anchoring the keratinocytes onto the basement membrane
damage between lowest layer of bricks and the concrete foundation (BM)
Immunofluorescence can be used to detect IgG and C3 at the dermo-epidermal junction
describe pemphigus vulgaris
blisters are more flaccid
rupture easily, revealing the raw surface underneath
IgG disease
damage within the keratinocyte layers = acatholysis
what is pemphigus foliaceous
rarely see intact bullae as they are so thin and come off easily
‘roof coming appart’
IgG mediated
what is discoid eczema
flexural surfaces
presents with round plaques
common allergen for contact dermatitis and features
nickel
get hyperkeratosis
epidermis gets thicker
eczema = spongiotic - oedema between keratinocytes
what is plaque psoriasis
extensor surfaces
silvery plaques
7 day keratinocyte turnover
dilated vessels
what is lichen planus
lichenoid reaction pattern
T cell mediated
papules and plaques slightly purpleish in colour on wrists and arms
white lines in mouth (wickam striae)
like the BM has been destroyed by ‘loads of ants’
band-like lymphocytic infiltrate just under the epidermis
what is pyoderma gangrenosum
form of vasculitis
presents as an ulcer
often first manifestation of a systemic disease
what is sebhorreic keratosis
‘stuck on’ appearance
horn cysts under microscope
features of a BCC
rolled pearly edges, central ulcer, telangiectasia
arses from keratinocytes along the bottom of the epidermis
cells infiltrate through the BM
spread via nerves and lymphovascular system
locally infiltrative but don’t metastasis
what is bowens disease
SCC in situ
features of malignant melanoma
asymmetry, order irregularity, colours, diameter, EVOLUTION
melanocytes begin to migrate upwards through the epidermis (pagetoid spread)
thickness >4mm has very high mortality
