Histopath

Question 1

Where can the stratum lucidum be found?

Answer 1

Palms and soles

Question 2

What are the 6 types of inflammatory reaction patterns of the skin?

Answer 2

1. Vesiculobullous
2. Spongiotic
3. Psoriasiform
4. Lichenoid
5. Vasculitic
6. Granulomatous

Question 3

Describe the underlying pathophysiology of bullous pemphigoid

Answer 3

It is an autoimmune reaction. Anti-hemidesmosomes IgG antibodies and complement attack the stratum basale which causes the whole layer to lift up and attracts eosinophils which release elastase and cause further damage. Fluid builds up and whole epidermis lifts up, forming a tense bulla

Question 4

How do you diagnose bullous pemphigoid?

Answer 4

Immunofluorescence IgG and C3

You’ll see a band along the basement membrane

Question 5

Describe the underlying pathophysiology of pemphigus vulgaris

Answer 5

Anti-desmosome antibodies (IgG) attack the connections between keratinocytes and thus the keratinocytes start to free float and fluid collects intraepidermally.

Can use immunofluorescence to demonstrate IgG around the individual keratinocytes

Type 2 hypersensitivity

Question 6

Describe the underlying pathophysiology of pemphigus foliaceus

Answer 6

Antibodies (IgG related) against the connections in the stratum corneum and hence it comes away. You don’t see bullae in this condition as they are so thin that they tear away after a shor tperiod of time, leaving an excoriated area.

Use immunofluorescence for diagnosis

Question 7

What is the inflammatory rection pattern seen in eczema called?

Answer 7

Spongiotic - this means that there is oedema/fluid between the keratinocytes

Question 8

Describe the long term skin changes in eczema

Answer 8

Epidermis starts to get thicker over time - lichenification

Question 9

Name the inflammatory reaction pattern seen in psoriasis

Answer 9

Psoriasiform

Question 10

Auspitz’s sign

Answer 10

Seen in psoriasis

Pin point bleeding upon removal of the silvery plaques.

Due to the fact that the epidermis is thinner and corresponds to the tips of the dermal papillae and vessels which are dilated and more prominent.

Question 11

Koebner phenomenon

Answer 11

Appearance of skin lesions along lines of trauma

Psoriasis

Question 12

What is the normal transit time from stem cell to keratinocyte and what is it in psoriasis?

Answer 12

Normal - 56 days

Psoriasis - 7 days

Question 13

Which layer of the epidermis do you lose in psoriasis?

Answer 13

Granulosum

However, epidermis thickens due to high proliferation rate

Question 14

Munro’s microabscesses

Answer 14

Accumulation of neutrophils within the stratum corneum in psoriasis (cardinal sign)

Useful as it contrasts the eosinophils you see in eczema

Question 15

Describe the symptoms of lichen planus

Answer 15

Itchy, purpley, red, patches/plaques in the extensor surfaces and distal surfaces

Classic white lines in the mouth - Wickham striae

Question 16

Wickham striae

Answer 16

​Classic white lines in the mouth seen in lichen planus

Question 17

Describe the underlying pathophysiology of lichen planus

Answer 17

T lymphocytes attack the basal layer of keratinocytes in the epithelium. You can’t see where the epidermis stops and dermis starts as the bottom layer goes through apoptosis. You get a classic band-like inflammation underneat

Question 18

What is a seborrhoeic keratosis?

Answer 18

One of the commonest benign lesions

Look cauliflowerish, pigmented and all over the place in the elderly

Completely harmless as it is due to keratinocytes proliferating in an orderly manner.

Histologically you may see large windows called keratin horn cysts

Question 19

Describe the pathophysiology of sebaceous cysts

Answer 19

Epidermis is invaginated and got caught up within the dermis and it produces the keratin

Question 20

Describe features of a basal cell carcinoma

Answer 20

Central ulceration

Raised pearly rim around the edge

Nicknamed rodent ulcer as it tends to burrow away into the nooks and crannies of the face

Rarely metastasises

Question 21

Bowen’s Disease

Answer 21

Precancer (SCC)

Basically full thickness dysplasia but has not broken through the basement membrane

Question 22

What is perineural invasion?

Answer 22

This is when the tumour wraps around a nerve

Question 23

What causes naevi?

Answer 23

Melanocytes proliferate and acumulate

Question 24

Describe the 3 types of naevi

Answer 24

1) Junctional - melanocytes in epidermis (younger population)
2) Compound - melanocytes in epidermis and dermis
3) Intradermal -melanocytes in dermis

Intradermal more common as you get older as melanocytes tend to migrate downwards as you get older

Question 25

What is pagetoid spread?

Answer 25

This is when there is an upward migration of melanocytes which shouldn’t happen (should be migrating downwards and become smaller). This indicates lack of maturity as the size of melanocytes are uniform throughout

Question 26

When is pagetoid spread normal?

Answer 26

In pregnancy (not a melenoma)