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Year 2 - Cancer > Cancer 15 > Flashcards

Cancer 15 Flashcards

1
Q

what is the structure of the epidermis?

A
  • Stratum corneum
  • Stratum lucidum
  • Stratum granulosum
  • Stratum spinosum
  • Stratum basale

Come Lets Get Sun Burn

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2
Q

how do keratinocytes change throughout the layers of the skin?

A
  • the basal layer of keratinocytes is resting on the basement membrane
  • as keratinocytes proliferate they move up the layers of the epidermis, they differentiate and then end up in the stratum corneum
  • the stratum corneum is a layer of keratinocytes that have lost their nuclei and mainly consist of keratin
  • the stratum corneum provides the barrier function of the skin
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3
Q

what are the main cells in the epidermis?

A
  • Keratinocytes
  • Melanocytes - sits on the basement membrane and produces melanin
  • Langerhans cells - APCs found within the epidermis
  • Merkel cells - involved in sensation
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4
Q

what are the types of skin cancer?

A
  • Keratinocyte derived

​Basal cell carcinoma

Squamous cell carcinoma

  • Melanocyte derived

Malignant melanoma​

  • Vasculature derived

​Kaposi’s sarcoma = arises from the endothelium of the lymphatics

Angiosarcoma = arises from the endothelium of blood vessels

  • Lymphocyte derived

​Mycosis fungoides = lymphoma that is specific to the skin

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5
Q

what are examples of genetic syndromes causing skin cancer?

A
  • Gorlin’s Syndrome
  • Xeroderma pigmentosum
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6
Q

what is gorlins syndrome?

A
  • Autosomal dominant condition where the individual has a defect in the PTCH gene
  • germline condition so only requires one mutation to occur
  • these patients have multiple basal cell carcinomas throughout their lives
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7
Q

what is xeroderma pigmentosum?

A
  • rare condition caused by a mutation in a gene involved in DNA repair
  • Nucleotide excision repair is faulty in these patients so they develop many skin cancers
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8
Q

what viral infections might cause skin cancer?

A
  • human herpes virus 8 causes kaposis sarcoma
  • HPV causes Squamous cell carcinoma
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9
Q

what skin cancer does UV light cause?

A
  • Basal Cell Carcinoma
  • Squamous Cell Carcinoma
  • Malignant melanoma
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10
Q

what examples of immunosuppression might cause skin cancer?

A
  • Drugs e.g. azathioprine, cyclosporin
  • HIV
  • Old age
  • Leukaemia
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11
Q

who is skin cancer most prevalent in?

A
  • in white people there is increase in prevalence
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12
Q

what are the features of Malignant Melanoma?

A

dark, lumpy, abnormal

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13
Q

what are the features of basal cell carcinoma?

A
  • shiny and red
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14
Q

how far do the following wave lengths reach?

UVC

UVB

UVA

?

based on this which wavelength is most prevalent in skin cancer?

A
  • UVC does not penetrate the atmosphere
  • UVB will reach the sea level
  • UVA will reach the dead sea level

UVB is most significant for skin cancer development

UVA is the second most significant for skin cancer development but less so than UVB

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15
Q

why is sunlight essential for life?

A
  • Essential for photosynthesis
  • Provides warmth
  • Effect on human mood
  • Stimulates the production of vitamin D in the skin
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16
Q

how does UVB cause skin carcinogenesis?

A
  • UVB directly induces mutations in DNA
  • Affects the pyridines and causes crosslinking producing Cyclobutane pyrimidine dimers and 6-4 pyrimidine pyrimidone photoproducts
  • these are usually quickly repaired by nucleotide excision repair
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17
Q

how does UVA cause skin carcinogenesis?

A
    • forms cyclobutane pyrimidine dimers but less effectively than UVB
  • generates free radicals that damage the DNA
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18
Q

what genes does UV light damage?

A
  • Cell division
  • DNA repair
  • Cell cycle arrest

however photoproducts (mutations) are normally removed by a process called nucleotide excision repair

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19
Q

what is Xeroderma pigmentosum?

A
  • genetic condition with defective nucleotide excision repair
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20
Q

features of Xeroderma pigmentosum?

A
  • patients with Xeroderma pigmentosum have defective nucleotide excision repair
  • when the DNA is not being repaired properly patients develop cancer at a very young age
  • they will develop BCCs, SCCs and melanomas
  • they are also very photosensitive and have dry skin
  • they sometimes also have ocular and neurological problems
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21
Q

Summarise the mutations that cause cancer?

A
  • Mutations that stimulate uncontrolled cell proliferation
  • Mutations that alter responses to growth stimulating/repressing factors
  • Mutations that inhibit apoptosis
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22
Q

what happens in sunburn?

A
  • UV leads to keratinocyte apoptosis
  • Sun burn’ cells are apoptotic cells in UV overexposed skin
  • Apoptosis removes UV damaged cells in the skin which might otherwise become cancer cells
23
Q

explain Photocarcinogenesis:

A
  • overexposure to UV radiation causes DNA damage in the keratinocytes
  • the DNA can then get repaired and return to being a normal cell
  • if the damage is very severe it might undergo apoptosis
  • If this damage is accompanied by appropriate mutations in other cancer-promoting genes it might cause cancer
24
Q

how does UV light affect the immunocompetence of the skin?

how might this be helpful?

A
  • UVA and UVB affect the expression of genes involved in skin immunity
  • they deplete Langerhans cells in the epidermis
  • this causes reduced skin immunocompetence

( this is the basis of using UV phototherapy to treat psoriasis it immunocompromised the skin so the inflammatory condition gets better) but this does increase risk of skin cancer

25
Q

The mechanism by which UV therapy increases the risk of skin cancer:

A
  • UV light can act on keratinocytes and cause DNA damage that could lead to it becoming a malignant cell
  • if the Langerhans cells were working properly they would induce an immune response and cause cell death in the damaged cell
  • but if the Langerhans cells are not working properly they are unable to knock out the damaged cells and this might result in cancer
26
Q

what are Fitzpatrick Phototypes?

A
  1. Always burns never tans
  2. Usually burns, sometimes tans
  3. Sometimes burns, usually tans
  4. Never burns, always tans
  5. Moderate constitutive pigmentation = Asian
  6. Marked constitutive pigmentation = Afrocaribean
27
Q

what is the function of melanin?

A
  • Responsible for skin color
  • produced by melanocytes in the basal layer of the epidermis
  • ones skin colour depends on the amount and type of melanin produced not the density
28
Q

what is the structure and function of melanocytes?

what do the keratinocytes do?

A
  • melanocytes are dendritic and they interlock with about 30 or so keratinocytes
  • melanocytes produce melanin which is packed into melanosomes
  • the melanosomes are passed down the process and are taken up by the keratinocytes
  • The keratinocytes put the melanosomes around their nucleus, which protects it from UV damage
29
Q

How does tanning work?

A
  • in pale skin types under the influence of UV light keratinocytes make melanocyte-stimulating hormone
  • this has paracrine effects on the melanocytes to make more melanin
30
Q

xxxx

A

xxxx

31
Q

xxxx

A

xxxx

32
Q

what are the two types of melanin that are formed?

A
  • Eumelanin - produced by people with dark hair and dark skin
  • Phaeomelanin - produced by those with red/light hair and fair skin
33
Q

which gene controls melanin?

how is melanin formed?

A
  • The amounts of melanin are regulated by the MCR1 gene
  • Melanin is formed from tyrosine
34
Q

how many polymorphisms in the melanin gene?

A
  • >20 gene polymorphisms in this gene
35
Q

what is malignant melanoma?

what might it be caused by?

mortality rate?

A
  • Malignant tumor of melanocytes
  • melanocytes become abnormal and have atypical cells and atypical architecture
  • Can be caused by UV exposure or Genetic factors
  • high risk of metastasis and highest mortality
36
Q

what is Lentigo Maligna?

A
  • Proliferation of malignant melanocytes within the epidermis
  • no risk of metastasis
  • considered to be a pre- melanoma state
  • often has an irregular shape and border
37
Q

what is lentigo maligna melanoma ?

A
  • this is a large area of lentigo maligna
  • that might become invasive
38
Q

how does the malignant melanoma superficially spread?

A
  • Lateral proliferation of malignant melanocytes
  • They invade the basement membrane
  • It is invasive and it grows outwards
  • There is now a risk of metastasis as the melanoma is below the basement membrane
39
Q

how might one diagnose a superficial spreading malignant melanoma?

A

ABCDE -

Asymmetry

Border irregularity

Colour variation (dark brown=black)

Diameter >0.7

Erythema

40
Q

what are some features of superficial spreading malignant melanoma?

A
  • sometimes has a pale patch in the middle called area of regression
  • tumour might of disappeared because it has burned itself out or the immune system has destroyed it
  • has a high association with metastasis
41
Q

what are the main risk factors for Development of Melanoma ?

A
42
Q

What is Acral Lentiginous Melanoma?

A
  • melanomas that appear on
43
Q

what is Amelanotic Melanoma?

A
  • Sometimes melanomas don’t produce pigments so it appears pink
  • might metastasis to the lymph nodes
44
Q

what is a Keratoacanthoma?

A
  • no risk of metastasis
  • grows rapidly then disappears
  • it is a benign version of SCC
45
Q

what is Squamous Cell Carcinoma ?

what is it caused by?

A
    • Malignant tumour of keratinocytes
  • Risk of metastasis
  • it is caused by Immunosuppression, May occur in scars or scarring processes , UV exposure, HPV
46
Q

features of well-differentiated Squamous Cell Carcinoma?

A
  • well-differentiated SCC might have a keratin horn which means it is producing keratin
47
Q

where are common sites of Squamous Cell Carcinoma?

A
  • lower legs are common due to sun exposure in women
  • protruding ears
48
Q

what is basal cell carcinoma?

A
  • Malignant tumour arising from the basal layer of the epidermis
49
Q

what are causes of basal cell carcinoma?

A
  • Sun exposure
  • Genetics
50
Q

how do basal cell carcinomas grow?

A
  • These are slow-growing
  • they invade tissues but they do not metastasise
51
Q

what are nodular BCCs?

A
  • It is pearly, has a rolled edge and there is telangiectasia
  • a localised collection of distended blood capillary vessels = a localised collection of distended blood capillary vessels
  • telangiectasia looks branching
52
Q

what is Mycosis Fungoides?

A
  • This is a cutaneous T cell lymphoma
  • affects the skin causing red patches
  • very slowly progression
53
Q

what is Kaposi’s Sarcoma?

A
  • HIV and HHV8 associated
  • tumour of the endothelium of the lymphatics
54
Q

what is Epidermodysplasia Verruciformis?

A
  • this is a rare autosomal recessive condition that predisposes to HPV induced warts and SCCs
  • the pale areas are abnormal

Year 2 - Cancer (15 decks)

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