HistoPath - Skin

Question 1

What are the layers of the skin

Answer 1

Epidermis, dermis, SC fat

Epidermis:
- Stratum corneum
- Stratum lucidum
- Stratum granulosum
- Stratum spinosum
- Stratum basale
Dermis
Subcutaneous fat

Question 2

What is within the dermis layer of the skin

Answer 2

Blood vessels
Sweat glands
Hair follicles
Sebaceous glands
Nerve fibres

Question 3

How long does it take for skin cells to complete their life cycle

Answer 3

28-40 days

Question 4

Describe the following inflammatory reaction patterns: spongiotic, lichenoid, vesiculobullous, psoriasiform, granulomatous, vasculaopathic

Answer 4

Spongiotic: intraepidermal intercellular OEDEMA
Lichenoid: basal cell damage, interface dermatitis
Psoriasiform: epidermal HYPERPLASIA
Vesiculobullous: blistering within or beneath the epidermis
Granulomatous: granulomas e.g. TB, sarcoid
Vasculaopathic: pathological changes in cutaneous blood vessels

Question 5

Give an example of spongiotic inflammatory skin disease

Answer 5

Eczema - intra-epidermal intercellular oedema

Question 6

Give an examples of lichenoid inflammation

Answer 6

Lichen planus
Eyrthema multiforme
toxic epidermal necrolysis (TEN)
Stevens-Johnson syndrome (SJS)

Question 7

What is the pathophysiology of lichen planus and how does it present

Answer 7

T-cell mediated destruction of bottom keratinocytes → band-like inflammation
Cannot distinguish between dermis and epidermis
Presents with purple/red papules + plaques on the wrists and arms
White lines in the mouth (Wickham striae)

Question 8

What is the pathophysiology of plaque psoriasis

Answer 8

Psoriasiform inflammation of the skin on the extensor surfaces
Silver/white plaques
Rapid keratinocyte turnover time (7 days) → thickened epidermis → layer of parakeratosis on the top → Psoriasiform hyperplasia
The stratum granulosum disappears as there is not enough time to form it → dilated vessels
Munro’s microabscesses (recruitment of neutrophils)

Question 9

What are vesiculobullous reactions and give examples

Answer 9

Autoimmune - Abs against the epidermis
Bullous pemphigoid
Pemphigus vulgaris
Pemphigus foliaceus

Question 10

How does bullous pemphigoid present and how is it diagnosed

Answer 10

Elderly
Tense bullae (dermo-epidermal junction)
- Flexor surfaces
- May be precipitated by PD-1 and DPP4 inhibitors

Diagnosis is via immunofluorescence → Detects IgG anti-hemidesmosome

Question 11

What is the pathophysiology of bullous pemphigoid

Answer 11

Auto-immune: IgG and C3 attack the hemidesmosomes of the epidermal basement membrane → SUB-epidermal bullae (Deep)
Eosinophils are recruited → releases elastase → damages anchoring proteins → fluid fills the gap between BM and epithelium

Question 12

How does pemphigus vulgaris present and how is it diagnosed

Answer 12

Flaccid blisters (mucous membranes)
- Ruptures easily
- Skin and mucosal membranes

Immunofluorescence → chicken-wire pattern (IgG surrounding)

Question 13

What is the pathophysiology of pemphigus vulgaris

Answer 13

IgG attacks desmosomes between the keratin layers (acantholysis) → loss of intracellular connections
T2 HS reaction
Superficial bullae

Question 14

Describe pemphigus foliaceus (presentations, pathophysiology, diagnosis)

Answer 14

SUPERFICIAL
Top layer is very thin so never blisters
IgG-mediated to desmoglein 1 – outer layer of stratum corneum shears off
Diagnose with immunofluorescence

Question 15

What is the histology for eczema

Answer 15

Acute: spongiosis (oedema between keratinocytes), inflammatory infiltrate in dermis, dilated dermal capillaries

Chronic: acanthosis, hyperparakeratosis, lichenification, crusting, scaling, T cells, eosinophils

Question 16

What are the clinical signs of psoriasis

Answer 16

Auspitz’ sign: rubbing the skin causes pin-point bleeding
Koebner phenomenon: lesions form at the site of trauma

Question 17

What is the difference between rosacea and pityrasis rosea

Answer 17

Rosacea = redness, pimples, swelling, VD treated, remits spontaneously- emollients, uv-b/ acyclovir, 10-35 year olds, hhv6/7
Pityrasis rosea = herald patch, eruption smaller , older children + young adults

Question 18

Describe basal cell carcinomas appearance and histology

Answer 18

Benign
Rolled, pearly-edge, central ulcer, telangiectasia
“Rodent ulcer” as it burrows away
Occurs in sun-exposed areas

Histo: dysplastic change, PCTH mutation, bottom keratinocytes affected, cannot invade BM (cannot met)

Question 19

What is the pre-malignant stage of melanoma called

Answer 19

Bowen’s disease (becomes malignant when it invades the BM)
Squamous cell carcinoma in situ
Keratinocytes become more pleiomorphic and larger with mitotic figures

Question 20

Describe squamous cell carcinomas and its histology

Answer 20

Poorly to well differentiated
Poorly = cannot determine original cell lineage
Per-neural invasion may occur

Histo: Pleomorphic squamous epithelial cells arising from the epidermis and extending into the dermis

Question 21

What are the types of benign naevus

Answer 21

Junctional: melanocytes nest in the epidermis, flat and coloured
Compound: nests in the epidermis and dermis, raised area, surrounding by flat pigmented area
Intradermal: nests in the dermis, raised area, skin coloured or pigmented

Question 22

What are the characteristics of a malignant melanoma lesion

Answer 22

ABCDE – Asymmetry, Border, Colour, Diameter, Evolution

Asymmetrical
Irregular border
Variable pigmentation
Bleeding
Size >4mm
Itchy
Growing

Question 23

What is the histology of malignant melanoma

Answer 23

Pagetoid spread - junctional melanocytes move up through the dermis (vertical growth) instead of maturing and dropping out the dermis
Atypical Melanocytes - mitotic figures
Spreads to lymph nodes > blood

Question 24

How is malignant melanoma staged

Answer 24

“Breslow Thickness”, along with ulceration, lymphovascular invasion, perineural invasion, Clark level, Microsatellites, TILs, Regression, Mitotic index

Question 25

What are the subtypes of malignant melanoma

Answer 25

Lentigo maligna melanoma: occurs on sun exposed areas of elderly Caucasians, flat, slowly growing black lesion
Superficial spreading malignant melanoma: irregular borders with variation in colour
Nodular malignant melanoma: can occur on all sites, more common in the younger age group.
Acral Lentiginous melanoma: occurs on the palms, soles, and subungual areas

Question 26

Describe seborrheic keratosis and its histopathology

Answer 26

“Cauliflower”, pigmented, gets caught on clothing (and taken off)
Stuck-on appearance, harmless and benign

Lots of growth and ordered proliferation
Ordered and benign growth
“Horn cysts” – epidermis entrapping keratin

Question 27

Describe sebaceous cysts

Answer 27

Transluminates, central punctum, circumscribed, hot
Squamous cell lining surrounding the cyst