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MCD Cancer > Skin cancer > Flashcards

Skin cancer Flashcards

1
Q

what are the 3 main layers of the skin?

A

epidermis (top)
dermis (middle)
hypodermis (bottom with subcutaneous tissue)

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2
Q

what are the layers of the epidermis (the top layer)?

what cells do they contain?

A 
o Stratum corneum 
– dead keratinocytes.
o Stratum lucidum.
o Stratum granulosum.
o Stratum spinosum 
– dendritic cells.
o Stratum basale 
– melanocytes, merkel cells, dividing cells
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3
Q

what are the origins of skin cancers? [4]

A
  • keratinocyte derived
  • melanocytes derived
  • vasculature derived
  • lymphocyte derived
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4
Q

name the keratinocyte derived cancers

A

1) BCC
(Basal Cell Carcinoma)
- highest incidence, least aggressive

2) SCC
(Squamous Cell Carcinoma).
aka Non-Melanoma Skin Cancer (NMSC).
- second highest incidence, more aggressive

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5
Q

name a melanocyte derived cancer

A

malignant melanoma

low incidence

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6
Q

name the vasculature derived cancers

A

Kaposi’s sarcorma (lymphatic epithelial cell)

angiosarcoma

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7
Q

name the lymphocyte derived cancers

A

mycosis fungoides

T cell lymphoma

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8
Q

what are keratinocytes and melanocytes exposed to?

A

UV and genetic mutations

when they proliferate they move from the basement membrane level towards the top of the epidermis

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9
Q

what are the 4 causes of skin cancer?

A
  • genetics syndromes
  • viral infections
  • UV light exposure
  • immunosuppression
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10
Q

name conditions caused by genetic syndromes

A

Gorlin’s syndrome and xeroderma pigmentosum

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11
Q

name conditions caused by viral infections

A

Kaposi’s sarcoma (HHV8) - vasculature derived

SCC (HPV)- keratinocyte derived

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12
Q

name conditions caused by UV light exposure

A

BCC
SCC
malignant melanoma

(increase in aggressivesness, decrease in incidence)

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13
Q

name the immunosuppressive causes of skin cancers

A

drugs
age
HIV
leukaemia

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14
Q

who are mostly affected by malignant melanomas?

A

those with pale skin (caucasian)
highest in the south-west of England (more sunshine)

low among darker skins ethnicities

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15
Q

describe a malignant melanoma

A

irregular margin and is dark-coloured

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16
Q

describe a BCC

A
  • pearly appearance, glistens, greyish

- has dilated small capillaries on the surface (telangiectasia)

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17
Q

what are the types of UV radiation

A

o UVA – 310-400nm. Penetrates to deep sea level
o UVB – 280-310nm. Penetrates to ground level.
o UVC – 100-280nm. Does not penetrate ozone.

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18
Q

which of the UV radiation types account for mutations in the skin

A

UVA>UVB

UVA 100x more penetrating than UVB.

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19
Q

what does UVA contribute to?

A

Major cause of skin ageing as it will reach the collagen in the skin
and contributes to skin carcinogenesis (not as much as UVB)

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20
Q

how does UVA contribute to carcinogenesis?

A
  • Forms Cyclobutane pyrimidine dimers i.e. cross linking but less efficiently than UVB.
  • Forms free radicals to damage DNA and cell membranes
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21
Q

how does UVB contribute to carcinogenesis?

A

MAJOR contributor:

  • Induces direct abnormalities in skin DNA – e.g. mutations.
  • Induces photoproducts – affects pyramidines (C, T) bases, e.g. cyclobutane pyrimidine dimers (e.g. T=T, T=C, C=C).
  • 6-4 pyrimidine pyrimidine photoproducts.
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22
Q

how how photoproduct resulting from UVB damage, mainly, repaired?

A

nucleotide excision repair

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23
Q

how can UVA be used to treat psoriasis? what is the risk?

A

PUVA (+psoralens)

increased risk of skin cancer

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24
Q

what conditions is caused by defective nucleotide excision repair (genetic)?

A

xeroderma pigmentosum

they develop skin cancer pretty early with little UV exposure

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25
Q

what are the benefits of sunlight?

A

photosynthesis
warmth from IR
human mood effects
production of VitD

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26
Q

what is sun burn?

A

UV light causes keratinocyte cell apoptosis in the epidermis

histology- this shows up black

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27
Q

what are the immunomodulatory effects of UV light? this is the basis for the treatment for what condition?

A

UVA/B affect expression of genes:

  • deplete Langerhans cells in the epidermis
  • decreased skin immunocompetance
  • UV phototherapy for psoriasis BUT also further increases cancer chances.
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28
Q

what mutation can lead to photocarcinogenesis?

A

p53 mutations leads to defective repair and apoptosis

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29
Q

how does the response to UV differ with host?

A

o 1 – always burns, never tans.
o 2 – usually burns, sometimes tans.
o 3 – sometimes burns, usually tans.
o 4 – never burns, always tans.

o 5 – moderate constitutive pigmentation – Asian.
o 6 – moderate constitutive pigmentation – Afrocaribean.

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30
Q

what produces melanin and what is it derived from?

A

melanosomes in melanocytes ,in the basal layer of the epidermis, produce melanin

melanin is derived from tyrosine

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31
Q

why does pigmentation differ among ethnicities?

A

people have roughly the same amount of melanocytes in the skin but darker people just produce more melanin with their cells than fairer people

people also produce different types of melanin

i.e. a different amount and type of melanin is produced among people

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32
Q

how is melanin made use of when produced by melanocytes?

A

once produced in the basal layer it is transported (melanosome transfer) up spines that go the keratinocytes

they pass into the cells and coat the nuclei within so the protect it from UV damage

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33
Q

what gene encodes melanin?

A

MCR1 gene

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34
Q

what are the types of melanin and what enables these types of be derived?

A

> 20 polymorphisms in the MC1R gene exist, enabling the 2 types of melanin to exist

 Eumelanin
– brown or black.
 Phaeomelanin
– yellowish or reddish.

the type of melanin expressed depends on the polymorphism

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35
Q

what is the biochemical pathway in melanin production?

A

Tyrosine –>DOPA –> Dopaquinone –> Eumelanin or Phaeomelanin –> melanin

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36
Q

what is the difference between a malignant melanoma and lentigo maligna?

A

malignant melanoma has a risk of metastasis

lentigo maligna has no risk of metastasis (confined to epidermis)

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37
Q

what is the cause of malignant melanoma?

A

UV and genetic risk factors

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38
Q

what is a hallmark of melanoma?

A

abnormal melanocyte position

they should be at the basal layer but in melanoma they travel upwards and in other directions

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39
Q

describe lentigo maligna

A

o Irregular shape.
o Light & dark colours.
o Size usually >2.0cm.

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40
Q

what happens when the malignant melanocytes proliferate laterally? can they metastasise?

A

superficial spreading malignant melanoma

this has a risk of metastasis as it invades the basement membrane

41
Q

how are malignant melanomas diagnosed?

A 
o A – Asymmetry.
o B – Border irregularity.
o C – Colour variation.
o D – Diameter >0.7mm (?) and increasing.
o (E – Erythema).
42
Q

what does a patchy melanoma indicate?

A

immune response has occurred so the melanoma has regressed but this could also mean that it has metastasised

43
Q

what happens when malignant melanocytes proliferate vertically? can they metastasise?

A

Nodular Malignant Melanoma (darker in appearance)

this is with no previous horizontal growth

risk of metastasis

44
Q

what happens when the malignant melanocytes proliferate vertically WITH previous horizontal growth?

A

Nodular Melanoma arising within superficially spreading malignant melanoma

here the prognosis becomes worse

45
Q

what is aural lentiginous melanoma?

A
  • A malignant melanoma affecting the palms and soles of the feet.
  • Occur in darker skinned people more often than lighter coloured skin people.
46
Q

what is amelanotic melanoma?

A

A melanoma where the cancer cells have lost the ability to create melanin.

47
Q

how is prognosis of a melanoma assessed? what does it measure and therefore indicate?

A

Breslow thickness:

  • measured from granular layer to bottom of tumour
  • states that the deeper the melanoma, the worse the prognosis.
48
Q

what are there risk factors that contribute to the development of a melanoma?

A
  • Family history
  • Intermittent burning exposure to unacclimatised skin
  • Skin types 1, 2.
  • UV light exposure
  • Atypical nevus syndrome.
  • Sunburns during childhood
  • Personal melanoma history.
49
Q

what are the 7 types of malignant melanomas?

A

1- Malignant Melanoma
2- Lentigo Meligna (Melanoma in situ)
3- Superficial Spreading Malignant Melanoma (horizontal)
4- Nodular Malignant Melanoma (vertical)
5- Nodular Melanoma arising within SSMM (vertical and horizontal)
6- Acral Lentiginous Melanoma (darker skinned people)
7- Amelanotic Melanoma (no melanin produced)

50
Q

what is SCC?

A

Malignant tumour of keratinocytes

can metastasise

51
Q

what causes SCC? [4]

A

UV
HPV
immunosuppression
scarring processes.

52
Q

name a variant of SCC

A

keratoacanthoma

53
Q

what is the feature that define differentiation level in SCC

A

keratin horns: indicates well differentiated carcinoma

absence of keratin indicates poor differentiation (keratinocytes no longer identifiable)

54
Q

what is BCC?

A

Malignant tumour arising from the basal layer of the epidermis which normally produces other skin cells

Locally destructive but not metastatic

55
Q

what are the causes of BCC?

A
  • sun exposure

- genetics.

56
Q

what are the features of BCC?

A 
o Slow growing.
o Invades but does not metastasise.
o Common on the face. 
- nodular or superficial 
- glistens with telangiectasia
57
Q

what is mycosis fungoides?

A

NOT a fungal condition as it was misclassified

its actually a T cell lymphoma of the skin which can take decades to progress

can be fatal and has internal organ involvement

58
Q

what are the associated causes of Kaposi’s sarcoma?

A

HVV8 and HIV

can occur in non-HIV patients

59
Q

what is Kaposi’s sarcoma?

A

A tumour of the endothelial cells of the lymphatics.

60
Q

what is epidermodysplasia verruciformis?

A

Rare autosomal condition.

Gives a predisposition to HPV-induced warts and SCCs.

61
Q

what is the main treatment for skin cancers?

A

surgery

62
Q

what is the main aetiological agent of skin cancer?

A

sunlight

others:

  • ionising radiation
  • viruses
  • tissue scarring
63
Q

which carcinoma type has the highest incidence?

A

basal cell carcinoma

64
Q

which carcinoma type has the lowest incidence?

how aggressive?

A

melanoma

the aggressiveness increases with decreasing incidence

65
Q

3 main types of skin cancer

A

basal cell carcinoma
squamous cell carcinoma
melanoma

66
Q

which type of skin is sensitive to sun light and have high incidence of skin cancer?

A

Fitzpatrick Skin Type 1

67
Q

what are the Fitzpatrick phenotypes for skin?

A 
1-6 
I – Always burns, never tans
II – Usually burns, sometimes tans
III – Sometimes burns, usually tans
IV – Never burns, always tans
V – Moderate constitutive pigmentation
VI – Marked constitutive pigmentation
68
Q

Fitzpatrick type I

A

always burns

never tans

69
Q

Fitzpatrick type II

A

usually burns

sometimes tans

70
Q

Fitzpatrick type III

A

sometimes burns

usually tans

71
Q

Fitzpatrick type IV

A

never burns

always tans

72
Q

Fitzpatrick type V

A

moderate constitutive pigmentation

73
Q

Fitzpatrick type VI

A

marked constitutive pigmentation

74
Q

what is the wavelength range of UVA?

A

310-400nm

75
Q

what is the wavelength range of UVB?

A

280-310nm

76
Q

which UV type will reach the earth’s surface more?

A

UVA
(100 times more)

therefore major cause of ageing and contributor to carcinogenesis

77
Q

how does UVA damage the skin?

A
  • free radical generation
  • T –> G transversions
  • membrane damage
78
Q

which wavelength is the major contributor to carcinogenesis?

A

UVB

most important

79
Q

how does UVB contribute to carcinogenesis?

A

forms pyrimidine dimers (using adjacent thymidine residues)

they covalently link when exposed

e.g. cyclobutane-butane dimers

80
Q

what is the wavelength range of UVC?

A

100-280 nm

filtered out by ozone

81
Q

what is the relationship between carcinogenicity and wavelength

A

the lower the wavelength, the closer to X-ray, the higher the carcinogenicity

the higher the wavelength, the closer to visible spectrum, the lower the carcinogenicity

82
Q

which chromosome is p53 coded on?

A

17q

83
Q

what role does p53 have in skin cancer?

A

UV sensitive
one mutated p53 is enough, even though it is a TSG, to have mutagenic effect

binds to DNA as tetramer regulating other genes

84
Q

what immune cells normally presents antigens to T cells for the destruction of tumour cells?

A

Langerhans cells (dendritic cells)

85
Q

what role do Langerhan cells have in skin cancer?

A

they are sensitive to UV and therefore their density is decreased so their APC role is compromised

86
Q

who and where is basal cell carcinoma most common?

A

in the elderly

seen on head and neck (areas of sun exposure)

87
Q

main feature of basal cell carcinoma

A

pearly appearance with telangiectasia

88
Q

what is squamous cell carcinoma?

- metastatic?

A

malignancy of epidermal keratinocytes due to UV

this one is metastatic unlike basal cell carcinoma
spreads to lymph nodes and other organs like the lung

[remember the lower the incidence, the higher the aggressiveness; BCC is higher in incidence than SCC]

89
Q

who and where is SCC most common?

A

the elderly

head and neck

90
Q

main features of SCC

A
  • may be ulcerated
  • hyperkeratotic (keratin horn–> well differentiated)
  • crusty or scaly
  • non-healing
91
Q

what is a melanoma?

- metastatic?

A

arises from melanocytes

highly metastatic: lymph nodes and organs (lung, brain, liver)

92
Q

in which people can melanoma occur?

A

in all even younger people

93
Q

what are the risk factors for melanoma?

A
  • Dysplastic naevae (moles)
  • Family history
  • Tanning beds
  • Intermittent, intense, early age sun exposure.
94
Q

how is epidermodysplasia verruciformis inherited?

aka Treeman syndrome

A

autosomal recessive

95
Q

which viral infection does epidermo. v predispose you to?

what does it do?

A

HPV

96
Q

what cancer can arise from epidermo.v?

A

squamous cell carcinoma

97
Q

how does HPV deactivate p53 in epidermodysplasia verruciformis?

A

E6 protein deactivates p53

98
Q

how does HPV infection in epidermodysplasia verruciformis lead to squamous cell carcinoma?

A
  • mild immunodeficiency leads to multiple viral warts
  • they become oncogenic in the sun
  • keratinocytes become infected
  • E6 deactivates p53

MCD Cancer (17 decks)

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