Pathology of the Skin

Question 1

Parakeratosis

Answer 1

Persistence of nuclei in the keratin layer, due to excessive differentiation of keratinocytes and high speed of turnover

Question 2

Hyperkeratosis

Answer 2

Increased thickness of keratin layer

Question 3

Acanthosis

Answer 3

Increased thickness of epithelium

Question 4

Papillomatosis

Answer 4

Irregular epithelial thickening

Question 5

Spongiosis

Answer 5

Oedema fluid between squamous appears to increase prominence of intercellular prickles

Question 6

What are the 4 main classifications of inflammatory skin disease?

Answer 6

1. Spongiotic (intraepidermal oedema)
2. Psorisiform (elongation of rete ridges)
3. Lichenoid (basal layer damage)
4. Vesiculobullous (blistering)

Question 7

Koebner Phenomenon

Answer 7

Refers to skin lesions appearing on lines of trauma

Question 8

What are the histological characteristics of Psoriasis?

Answer 8

Elongation, clubbing and fusion of the rate ridges, parakeratosis and superficial blood vessels

Question 9

What is the most common lichenoid disorder?

Answer 9

Lichen planus - Itchy flat topped violaceous papules

Question 10

What are histological features of lichen planus?

Answer 10

Irregular sawtooth acanthosis, pigment incontinence (pigments have dropped into the dermis due to damage to basal layer)

Question 11

Which antibodies are involved in pemphigus vulgaris and bullous pemphigoid?

Answer 11

IgG

Question 12

Which antibodies are involved in dermatitis herpetiformis?

Answer 12

IgA

Question 13

Pemphigus

Answer 13

Rare autoimmune bulls disease, of which there are 4 types - the most common being pemphigus vulgaris

Question 14

What is common to all variants of pemphigus?

Answer 14

Acantholysis - lysis of intercellular adhesion sites (cells all separate)

Question 15

In pemphigus vulgaris, what do the autoantibodies act against?

Answer 15

Desmoglein 3 (maintains desmosomal attachments)

Question 16

In bullous pemphigoid, what do the autoantibodies act against?

Answer 16

Antigen of the hemidesmosomes anchoring basal cells to basement membrane.

Question 17

What is a hallmark of immunofluorescence in BP?

Answer 17

Linear arrangement of IgG fluorescence along basement membrane

Question 18

What is the hallmark of dermatitis herpetiformitis?

Answer 18

Papillary dermal micro abscesses, particularly on the buttocks - look like ‘scratch lesions’

Question 19

In dermatitis herpetiformitis, what do the autoantibodies act against?

Answer 19

Gliadin component of gluten but cross react with connective tissue matrix proteins

Question 20

Sites of which glands is acne associated with?

Answer 20

Sebaceous glands - therefore face, upper back and anterior chest are affected

Question 21

What are the 4 main factors in the aetiology of acne?

Answer 21

1. Increased sebum production and thickness in response to androgens
2. Blockage of sebum foreign comedones
3. Builds up and ruptures causing inflammation
4. Bacterial infections

Question 22

Which gene determines the balance go pigment in skin and hair?

Answer 22

Melanocortin 1 receptor gene (MC1R)

Question 23

What does Eumelanin and Phaeomelanin cause in terms of hair colour?

Answer 23

Eumelanin causes all hair colours except red, phaeomelanin causes red hair

Question 24

What does MC1R do in terms of eumelanain and phaeomelanin, and what does defective copies do?

Answer 24

MC1R turns phaeomelanin into eumelanin. One defective copy causes freckles, 2 defective copies causes red hair and freckles

Question 25

What are ephilides?

Answer 25

Freckles - Patchy increase in melanin pigmentation over a few rete ridges in the skin (reflects clumpy distribution of melanocytes)

Question 26

What are actinic lentigines?

Answer 26

Age/Liver spots - due to localised proliferation of melanocytes in areas of chronic sun exposure. They don't fade in winter, unlike freckles.

Question 27

What are the 2 types of naevi?

Answer 27

Acquired (most common) or congenital

Question 28

What is the basis of acquired naevi?

Answer 28

During infancy the melanocytes:keratinocyte ratio breaks down at a number of cutaneous sites, allowing smoke naevi to form

Question 29

What is the developmental pathway for acquired naevi?

Answer 29

* 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

Question 30

What are dysplastic naevi?

Answer 30

'Funny-Looking moles' - may appear malignant, as they are variegated pigment, \>6mm diameter, asymmetrical

Question 31

What are the 2 main types of dysplastic naevi?

Answer 31

Sporadic (not inherited, common in freckly red-heads) and Familial (inherited condition with high risk of melanoma and have hundreds of dysplastic naevi)

Question 32

What is this?

Answer 32

Halo Naevi (peripheral halo of depigmentation )

Question 33

What is this guy?

Answer 33

Blue naevi (entirely dermal, and consist of pigment rich dendritic spindle cells)

Question 34

What are spitz naevi?

Answer 34

Naevi that usually occur \<20y, consiting of spindle/epitheliod cells. May mimic melanoma.

Question 35

Do most melanomas start 'denovo' or from dysplastic naevi?

Answer 35

De novo

Question 36

What are the 4 main types of malignant melanoma?

Answer 36

1. Superficial spreading (commonest) 2. Acral/mucosal lentiginos 3. Lentigo maligna 4. Nodular

Question 37

Radio-growth phase (RGP)

Answer 37

SSM, A/MLM and LMM all grow as macule outwards when either entirely in-situ or with dermal micro invasion

Question 38

Vertical growth phase (VGP)

Answer 38

Eventually the melanoma cells invade the dermis forming an expansile mass with mitoses - only this phase can metastasise

Question 39

Which melanomas shows no radio-growth phase, only vertical growth phase?

Answer 39

Nodular

Question 40

Breslow's Depth

Answer 40

Deepest tumour from granular layer mm

Question 41

What are the classifications of tumour types in terms of depth?

Answer 41

Question 42

What would a suffix of a 'b' mean in tumour type?

Answer 42

It would indicate ulceration

Question 43

What clearance should be given in excision of different types of lesions?

Answer 43

* 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

Question 44

What is the key difference between freckles and naevi/lentigines?

Answer 44

Freckles are increase in melanin, while naevi/lentigines are an increase in the number of melanocytes

Question 45

What are seborrheic keratoses?

Answer 45

Benign skin tumour that originates from keratinocytes. Appear as brown/black greasy lesions with a 'stuck on' appearance

Question 46

What is a dermatofibroma?

Answer 46

A dermatofibroma is a common benign fibrous nodule that most often arises on the skin of the lower legs.