Pathology of the Skin Flashcards
Parakeratosis
Persistence of nuclei in the keratin layer, due to excessive differentiation of keratinocytes and high speed of turnover
Hyperkeratosis
Increased thickness of keratin layer
Acanthosis
Increased thickness of epithelium
Papillomatosis
Irregular epithelial thickening
Spongiosis
Oedema fluid between squamous appears to increase prominence of intercellular prickles
What are the 4 main classifications of inflammatory skin disease?
- Spongiotic (intraepidermal oedema)
- Psorisiform (elongation of rete ridges)
- Lichenoid (basal layer damage)
- Vesiculobullous (blistering)
Koebner Phenomenon
Refers to skin lesions appearing on lines of trauma
What are the histological characteristics of Psoriasis?
Elongation, clubbing and fusion of the rate ridges, parakeratosis and superficial blood vessels
What is the most common lichenoid disorder?
Lichen planus - Itchy flat topped violaceous papules
What are histological features of lichen planus?
Irregular sawtooth acanthosis, pigment incontinence (pigments have dropped into the dermis due to damage to basal layer)
Which antibodies are involved in pemphigus vulgaris and bullous pemphigoid?
IgG
Which antibodies are involved in dermatitis herpetiformis?
IgA
Pemphigus
Rare autoimmune bulls disease, of which there are 4 types - the most common being pemphigus vulgaris
What is common to all variants of pemphigus?
Acantholysis - lysis of intercellular adhesion sites (cells all separate)
In pemphigus vulgaris, what do the autoantibodies act against?
Desmoglein 3 (maintains desmosomal attachments)
In bullous pemphigoid, what do the autoantibodies act against?
Antigen of the hemidesmosomes anchoring basal cells to basement membrane.
What is a hallmark of immunofluorescence in BP?
Linear arrangement of IgG fluorescence along basement membrane
What is the hallmark of dermatitis herpetiformitis?
Papillary dermal micro abscesses, particularly on the buttocks - look like ‘scratch lesions’
In dermatitis herpetiformitis, what do the autoantibodies act against?
Gliadin component of gluten but cross react with connective tissue matrix proteins
Sites of which glands is acne associated with?
Sebaceous glands - therefore face, upper back and anterior chest are affected
What are the 4 main factors in the aetiology of acne?
- Increased sebum production and thickness in response to androgens
- Blockage of sebum foreign comedones
- Builds up and ruptures causing inflammation
- Bacterial infections
Which gene determines the balance go pigment in skin and hair?
Melanocortin 1 receptor gene (MC1R)
What does Eumelanin and Phaeomelanin cause in terms of hair colour?
Eumelanin causes all hair colours except red, phaeomelanin causes red hair
What does MC1R do in terms of eumelanain and phaeomelanin, and what does defective copies do?
MC1R turns phaeomelanin into eumelanin. One defective copy causes freckles, 2 defective copies causes red hair and freckles
What are ephilides?
Freckles - Patchy increase in melanin pigmentation over a few rete ridges in the skin (reflects clumpy distribution of melanocytes)
What are actinic lentigines?
Age/Liver spots - due to localised proliferation of melanocytes in areas of chronic sun exposure. They don’t fade in winter, unlike freckles.
What are the 2 types of naevi?
Acquired (most common) or congenital
What is the basis of acquired naevi?
During infancy the melanocytes:keratinocyte ratio breaks down at a number of cutaneous sites, allowing smoke naevi to form
What is the developmental pathway for acquired naevi?
- In childhood, junctional naevus forms, where clusters of melanocytes develop at DEJ.
- Then in adolescence, compound naevus forms, with clusters at the epidermal junction and dermis.
- Finally in adulthood, the intradermal naevus forms where the cluster is fully dermal
What are dysplastic naevi?
‘Funny-Looking moles’ - may appear malignant, as they are variegated pigment, >6mm diameter, asymmetrical
What are the 2 main types of dysplastic naevi?
Sporadic (not inherited, common in freckly red-heads) and Familial (inherited condition with high risk of melanoma and have hundreds of dysplastic naevi)
What is this?
Halo Naevi (peripheral halo of depigmentation )
What is this guy?
Blue naevi (entirely dermal, and consist of pigment rich dendritic spindle cells)
What are spitz naevi?
Naevi that usually occur <20y, consiting of spindle/epitheliod cells. May mimic melanoma.
Do most melanomas start ‘denovo’ or from dysplastic naevi?
De novo
What are the 4 main types of malignant melanoma?
- Superficial spreading (commonest)
- Acral/mucosal lentiginos
- Lentigo maligna
- Nodular
Radio-growth phase (RGP)
SSM, A/MLM and LMM all grow as macule outwards when either entirely in-situ or with dermal micro invasion
Vertical growth phase (VGP)
Eventually the melanoma cells invade the dermis forming an expansile mass with mitoses - only this phase can metastasise
Which melanomas shows no radio-growth phase, only vertical growth phase?
Nodular
Breslow’s Depth
Deepest tumour from granular layer mm
What are the classifications of tumour types in terms of depth?
What would a suffix of a ‘b’ mean in tumour type?
It would indicate ulceration
What clearance should be given in excision of different types of lesions?
- If in-situ then clear by circa 5mm
- If invasive but 1mm thick tjem 2cm clearance
- Sentinel node biopsy (SNB) if >1mm thick or thinner with mitoses
What is the key difference between freckles and naevi/lentigines?
Freckles are increase in melanin, while naevi/lentigines are an increase in the number of melanocytes
What are seborrheic keratoses?
Benign skin tumour that originates from keratinocytes. Appear as brown/black greasy lesions with a ‘stuck on’ appearance
What is a dermatofibroma?
A dermatofibroma is a common benign fibrous nodule that most often arises on the skin of the lower legs.
