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MCD: Cancer > Skin cancer > Flashcards

Skin cancer Flashcards

1
Q

What are the different types of skin cancer?

A

Keratinocyte derived, e.g. basal cell carcinoma, squamous cell carcinoma (non-melanoma skin cancer)

Melanocyte derived, e.g. malignant melanoma

Vasculature derived, e.g. Kaposi’s sarcoma, angiosarcoma

Lymphocyte derived, e.g. mycosis fungoides

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2
Q

What are the different causes of skin cancer?

A

Genetic syndromes: Gorlin’s syndrome, xeroderma pigmentosum.

Viral infections: HHV8 in Kaposi’s sarcoma, HPV in SCC.

UV light: BCC, SCC, malignant melanoma.

Immunosuppression: drugs, HIV, old age, leukaemia.

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3
Q

What is the most important wavelength of light in skin carcinogenesis?

A

UVB (280-315)

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4
Q

What is the significance of UVB light in skin cancer?

A

Risk factor.

Directly induces abnormalities in DNA, e.g. mutations.

Induces photoproducts (mutations).

Affects pyrimidines, i.e. cytosine and thymine bases.

  • cyclobutane pyrimidine dimers, e.g. T=T, T=C, C=C.
  • 6-4 pyrimidine pyrimidone photoproducts.

Usually repaired quickly by nucleotide excision repair.

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5
Q

What is the significance of UVA in skin cancer?

A

Promotes skin carcinogenesis.

DNA forming cyclobutane butane pyrimidine dimers but less efficiently than UVB.

Free radicals which damage DNA and cell membrane.

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6
Q

How may UV-induced DNA damage be repaired?

A

Photoproducts are removed by nucleotide excision repair.

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7
Q

What is xeroderma pigmentosum?

A

Genetic condition with defective nucleotide excision repair.

Photosensitivity, early development of skin cancers.

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8
Q

What types of mutations can cause cancer?

A

Mutations that stimulate uncontrolled cell proliferation, e.g. abolishing control of the normal cell cycle (p53 gene).

Mutations that alter responses to growth stimulating/repressing factors.

Mutations that inhibit programmed cell death (apoptosis).

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9
Q

What is sunburn?

A

UV leads to keratinocyte cell apoptosis.

‘Sunburn’ cells are apoptotic cells in UV overexposed skin.

Apoptosis removes UV damaged cells in the skin which might otherwise become cancer cells.

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10
Q

What are the immunomodulatory effects of UV light?

A

UVA and UVB affect the expression of genes involved in skin immunity.

Depletes Langerhans cells in the epidermis.

Reduced skin immunocompetence and immunosurveillance- basis for UV phototherapy for e.g. psoriasis.

Further increases the cancer causing potential of sun exposure.

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11
Q

What determines the host response to UV?

A

Genetic influences, especially skin phototype.

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12
Q

What are the Fitzpatrick phototypes?

A

I: always burns, never tans.

II: usually burns, sometimes tans.

III: sometimes burns, usually tans.

IV: never burns, always tans.

V: moderate constitutive pigmentation- Asian.

VI: marked constitutive pigmentation- Afro-Caribbean.

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13
Q

What is melanin?

A

Melanin pigmentation is responsible for skin colour.

Produced by melanocytes within the basal layer of the epidermis.

Skin colour depends on the amount and type of melanin produced not the density of melanocytes (which is fairly constant).

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14
Q

What are the 2 types of melanin?

A

Eumelanin- brown or black.

Phaeomelanin- yellowish or reddish brown.

Melanin is formed from tyrosine via a series of enzymes.

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15
Q

What is the significance of the MCR1 gene?

A

>20 gene polymorphisms.

Variation in eumelanin:phaeomelanin produced.

Explains different hair colour and skin types.

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16
Q

What is malignant melanoma?

A

Malignant tumour of melanocytes.

Melanocytes become abnormal.

Atypical cells and architecture.

Risk of metastasis.

17
Q

What causes malignant melanoma?

A

UV exposure

Genetic factors

18
Q

What is lentigo maligna?

A

Melanoma in situ

Proliferation of malignant melanocytes within the epidermis

No risk of metastasis

Irregular shape

Light and dark brown colours

Size usually >2cm

19
Q

What is superficial spreading malignant melanoma?

A

Lateral proliferation of malignant melanocytes

Invade basement membrane

Risk of metastasis

20
Q

How is the ABCD rule used in the diagnosis of melanoma?

A

ABCDE rule

Asymmetry

Border irregular

Colour variation (dark brown-black)

Diameter >0.7mm and increasing

Erythema

21
Q

What is nodular malignant melanoma?

A

Vertical proliferation of malignant melanocytes (no previous horizontal growth)

Risk of metastasis

Nodular melanoma may arise within a superficial spreading melanoma:

  • downward proliferation of malignant melanocytes
  • following previous horizontal growth
  • nodule developing within irregular plaque- prognosis will become worse
22
Q

What is acral lentiginous melanoma?

A

Occur on soles of feet and palms of hands.

Occur in darker skinned people.

Often darkly pigmented lesion that starts off flat and can develop lumps within it.

23
Q

What is amelanotic melanoma?

A

Melanomas lose ability to make melanin.

Lesion lacks pigment.

24
Q

What are the different types of malignant melanoma?

A

Superficial spreading

Nodular

Lentigo maligna melanoma

Acral lentiginous

Amelanotic

25
Q

How is the prognosis of melanoma determined?

A

Breslow thickness- measurement from granular layer to bottom of tumour, in mm.

<1mm = superficial

>1mm = deep, high risk of metastasis

26
Q

What are the main risk factors for the development of melanoma?

A

Personal history of melanoma

Family history of dysplastic nevi or melanoma

Skin type I, II

Ultraviolet radiation

Sunburns during childhood

Intermittent burning exposure in unacclimatised fair skin

Atypical/dysplastic nevus syndrome

27
Q

What is squamous cell carcinoma?

A

Malignant tumour of keratinocytes.

Risk of metastasis.

28
Q

What are the causes of squamous cell carcinoma?

A

UV exposure

HPV

Immunosuppression

May occur in scars or scarring processes

29
Q

What is basal cell carcinoma?

A

Malignant tumour arising from basal layer of epidermis.

Slow growing.

Invades tissue, but does not metastasise.

Common on face.

30
Q

What are the causes of basal cell carcinoma?

A

Sun exposure

Genetics

31
Q

What is epidermodysplasia veruciformis?

A

Rare autosomal recessive condition.

Predisposition to HPV induced warts and squamous cell carcinomas.

32
Q

What is mycosis fungoides?

A

Lymphoma occurring in the skin.

(not caused by fungus)

Present with plaques and patches of erythematous scaly skin, which can turn into thick lesions (tumours).

Often spreads to lymph nodes and other organs.

Slowly progressive condition.

33
Q

What is Kaposi’s sarcoma?

A

Derived from the lymph endothelium.

HIV and HHV8 associated.

Purple papules and nodules.

MCD: Cancer (17 decks)

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