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YEAR 5: Histopathology SM > Histo: Skin Pathology > Flashcards

Histo: Skin Pathology Flashcards

1
Q

How thick is a normal epidermis, dermis and subcutaneous fat put together?

A

6 mm

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2
Q

What types of fibres are found in the layer underneath the epidermis?

A

Collagen

Elastic fibres

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3
Q

What structures are found within the dermis?

A
  • Blood vessels
  • Sweat glands
  • Hair follicles
  • Sebaceous glands
  • Nerve fibres
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4
Q

How is palmar-plantar skin different from skin in other parts of the body?

A

There are no sebaceous glands

There is a very thick corneal layer

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5
Q

Describe the effects of ageing on the skin.

A

Skin becomes fragile with very little epidermis

Collagen and elastic fibres are of poor quality

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6
Q

List some different types of inflammatory reaction patterns in the skin.

A
  • Vesiculobullous - forms bullae
  • Spongiotic - becomes oedematous
  • Psoriasiform - becomes thickened
  • Lichenoid - forms a sheeny plaque
  • Vasculitic - associated with vasculitis
  • Granulomatous - associated with granulomas
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7
Q

What is bullous pemphigoid? Describe the macroscopic appearance.

A
  • Vesiculobullous condition
  • Occurs in elderly patients on their flexor surfaces
  • Characterised by the formation of tense bullae

NOTE: it has a 10-20% mortality

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8
Q

Outline the pathophysiology of bullous pemphigoid.

A
  • Autoimmune disorder driven by IgG and C3 which attack the basement membrane
  • They recruit eosinophils which release elastase which further damages anchoring proteins (anchoring lower keratinocytes to the basement membrane)
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9
Q

How can bullous pemphigoid be definitively diagnosed?

A

Immunofluorescence will show IgG and C3 along the dermo-epidermal junction

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10
Q

Describe the macroscopic appearance of pemphigus vulgaris.

A

Blisters are flaccid meaning that they rupture easily exposing a red raw surface underneath

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11
Q

Outline the pathophysiology of pemphigus vulgaris.

A

IgG-mediated disease where the damage is occuring within the keratinocyte layers

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12
Q

What is acantholysis?

A
  • Loss of intercellular connections leading to loss of cohesion between keratinocytes

NOTE: this can occur due to a lot of dermatological conditions so immunofluorescence is needed to identify where the immune-mediated attack is taking place

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13
Q

Describe the macroscopic appearance of pemphigus foliaceus.

A
  • You rarely see intact bullae because they are so thin and fragile
  • You are likely to see some flaky remnants of old bullae
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14
Q

Outline the pathophysiology of pemphigus foliaceus.

A

IgG-mediated attack on the outer layer of keratinocytes (where the stratum corneum is found)

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15
Q

Describe the appearance of discoid eczema.

A
  • Very itchy and found on the flexural surfaces
  • Presents with discoid plaques
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16
Q

Describe the clinical presentation of contact dermatitis.

A
  • Itchy erythematous rash usually on the hands or feet (areas most commonly exposed to irritants)
17
Q

What is hyperparakeratosis?

A
  • Thickening of the skin on the surface where the patient has been scratching
  • The epidermis gets thicker
18
Q

What type of inflammatory skin reaction is eczema?

A

Spongiotic because there is oedema between the keratinocytes

19
Q

What are the main immune mediators in eczema?

A
  • T cell mediated
  • Eosinophils are also recruited

NOTE: this pattern is also seen in drug reactions

20
Q

Describe the typical presentation of plaque psoriasis.

A
  • This is a psoriasiform reaction pattern
  • Tends to present as silvery plaques on the extensor surfaces
21
Q

How is the keratinocyte turnover time different in psoriasis compared to normal skin?

A
  • Normal skin turnover = 50 days (time for keratinocyte to go from the bottom of the epidermis to the top)
  • Psoriasis = 7 days
  • This leads to thickening of the epidermis and you get a layer of parakeratosis at the top
22
Q

Which layer of the epidermis disappears in plaque psoriasis and why?

A

Statum granulosum - there is not enough time to form it

23
Q

What can neutrophil recruitment to the epidermis in plaque psoriasis cause?

A

Formation of Munro’s microabscesses

24
Q

What is lichen planus and what are its main features?

A
  • Lichenoid reaction pattern
  • T-cell mediated
  • Presents with papuls and plaques that are slightly purplish in colour on the wrists and arms
  • In the mouth it presents as white lines (Wickham striae)
25
Q

Describe the histological appearance of lichen planus.

A
  • Distinction between dermis and epidermis is difficult to see due to lymphocyte-mediated destruction of the bottom layer of keratinocytes
  • There is band-like lymphocytic infiltration just under the epidermis

NOTE: this is also seen in mycosis fungoides

26
Q

What type of inflammatory skin reaction results in pyoderma gangrenosum?

A

Vasculitic

27
Q

Describe the classic macroscopic appearance of seborrhoeic keratosis.

A

‘Stuck on’ appearance

28
Q

Which histological feature is classic of seborrhoeic keratosis?

A

Horn cysts - entrapped keratin surrounded by proliferating epidermis

NOTE: the epidermis is proliferating in an ordlerly manner

29
Q

Describe the appearance of sebaceous/epidermal cyst.

A
  • Smooth surface
  • Non-mobile
  • Tend to have a punctum
  • Can get infected/rupture
  • Can smell really bad
30
Q

Describe the histological appearance of a sebaceous cyst.

A
  • Looks like the surface has become invaginated to form a cyst
  • Lined by squamous epithelium
31
Q

Describe the macroscopic appearance of a basal cell carcinoma.

A

Rolled, pearly edge with a central ulcer and telangiectasia

32
Q

Describe the histological appearnace of a basal cell carcinoma.

A
  • Cancer arises from the keratinocytes along the bottom of the epiderms (basal cells)
  • They can infiltrate through the basement membrane
  • They are locally infiltrative but don’t metastasise
33
Q

What is Bowen’s disease?

A

Squamous cell carcinoma in situ

34
Q

Describe the histological appearance of a benign junctional naevus.

A
  • Melanocytes expand in their normal position sitting on the basal layer and form nests
  • They are circumscribed and uniformly pigmented
35
Q

Describe the normal migration of melanocytes as they mature.

A

As they mature they become smaller and go deeper

36
Q

What are some clinical signs suggestive of a malignant melanoma?

A
  • Assymetry
  • Border irregularity
  • Colours
  • Diameter
  • Evolution
37
Q

Describe the histological appearance of malignant melanoma.

A
  • Melanocytes start migrating upwards through the epidermis (pagetoid spread)
  • They become active and lose the ability to differentiate
  • Melanoma thickness > 4 mm has a > 50% mortality

YEAR 5: Histopathology SM (24 decks)

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