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Cancer > 15. Skin cancer > Flashcards

15. Skin cancer Flashcards

1
Q

What does the BM separate in the skin?

A

Epidermis and dermis

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2
Q

Which part of the skin do most cancers arise in?

A

Epidermis

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3
Q

Describe the structure of the epidermis (from the bottom up)?

A
  • Keratinocytes sit on BM - differentiate as they move up
  • Stratum basale
  • Stratum spinosum
  • Stratum granulosum
  • Stratum corneum (dead cells without nuclei)
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4
Q

Which cells are found in the epidermis?

A
  • Keratinocytes
  • Melanocytes
  • Merkel cells
  • Langerhans cells (APCs)
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5
Q

What are the different types of skin cancer?

A
  • Keratinocyte - basal cell carcinoma, squamous cell carcinoma
  • Melanocyte - malignant melanoma
  • Vasculature - Kaposi’s sarcoma, angiosarcoma
  • Lymphocyte - mycosis fungoides
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6
Q

What are the 2 most common skin cancers?

A

1) Basal cell carcinoma
2) Squamous cell carcinoma

(both keratinocyte derived)

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7
Q

What are the causes of skin cancer?

A
  • Genetic syndromes - Gorlin’s syndrome, Xeroderma pigmentosum (DNA repair disorder)
  • Viral infections - HHV8, HPV
  • UV light
  • Immunosuppression
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8
Q

What does a malignant melanoma look like?

A
  • Typically a pigmented lesion on the chest that stands out
  • Irregular edge and eccentrically placed nodule
  • Asymmetrical
  • Thickness determines prognosis and treatment (looked at with dermatoscope)
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9
Q

How has the incidence of malignant melanoma changed over the last 40 years?

A

Increase - in white skinned people

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10
Q

How has the incidence of basal cell carcinoma changed over the last 40 years and why?

A
  • Increased
  • Dramatic increase in Britain
  • Could be due to an ageing population, more holidays and behaviour to the sun/UV (sunbathing, sunbeds)
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11
Q

Which type of UV is filtered out by the ozone?

A
  • UVC completely

* UVB partially

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12
Q

Which UV type can penetrate all the way below sea level?

A

UVA (100 times more than UVB)

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13
Q

Which UV is the most significant in skin carcinogenesis out of UVA and UVB?

A

UVB

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14
Q

How does UVB affect DNA?

A

• Induces photoproducts, which affects the pyrimidines (C and T)
• Cyclobutane pyrimidine dimers form e.g. T=T, T-C, C=C
• 6-4 pyrimidine-pyrmidine photoproducts
• Usually repaired quickly by nucleotide excision repair
- if it is not repaired, and occurs in a gene essential for control of cellular proliferation => tumour

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15
Q

How does UVA affect DNA?

A
  • Also causes production of pyrimidine dimers like UVB, but less effectively
  • Free radical production - causing damage to DNA can cell membrane
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16
Q

Why does Xeroderma pigmentosum cause skin cancer?

A
  • Recessive genetic condition with defective nucleotide excision repair
  • Development of multiple skin cancers
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17
Q

What happens to cells when sun burnt (i.e. severe UV damage)?

A

Apoptosis

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18
Q

How does UV affect skin immunity?

A
  • Depletes Langerhans cells - removal of damaged cells and apoptosis doesn’t work very well
  • Reduces skin immunocompetence and immunosurveillance
  • Suppresses the inflammatory response
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19
Q

What are the Fitzpatrick phototypes?

A

How much melanin is in the skin
• 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 (Afrocaribbean)

20
Q

What are the dendritic cells of the epidermis?

A

Melanocytes and Langerhans cells

21
Q

Where are melanocytes found?

A

On the BM

22
Q

What is the ratio of melanocytes to keratinocytes?

A

1:5

23
Q

How is melanin produced in response to increased UV exposure?

A
  • Keratinocytes produce MSH
  • Paracrine effect on melanocyte - melanin production
  • Melanin packaged into melanosomes - travels down dendritic processes
  • Melanosomes are taken up by the keratinocytes and positioned in front of their nuclei
24
Q

How does the number of melanocytes compare in a light and dark-skinned person?

A

Same

25
Q

What are the 2 types of melanin formed from tyrosine?

A
  • Eumelanin - brown/black

* Phaeomelanin - yellow/reddish brown

26
Q

Which gene determines the production of melanin, and the eumelanin:phaeomelanin variation?

A

MCR1

27
Q

What is Lentigo Maligna?

A
  • Malignant melanoma
  • Restricted to epidermis
  • No risk of metastasis
  • Flat
  • Usually on face
  • Often occur in elderly patients
28
Q

What is superficial spreading malignant melanoma?

A
  • Atypical melanocytes in the epidermis
  • Invaded the dermis
  • Lateral and downwards proliferation
  • Invasion of BM - risk of metastasis
  • Regression possible - due to immune response
29
Q

How is a superficial spreading malignant melanoma diagnosed?

A
  • A - asymmetry
  • B - border irregular
  • C - colour variation (dark brown-black)
  • D - diameter >0.7mm
  • E - erythema (redness) or evolution (getting bigger)
30
Q

What is a nodular melanoma arising within a superficial spreading MM?

A
  • Type of malignant melanoma
  • Downward proliferation of malignant melanocytes, following previous horizontal growth
  • Nodule developing within an irregular plaque
  • Worse prognosis
  • Tumour may be erythematous - non-pigmented as tumour can’t make melanin
31
Q

What is an acral lentiginous melanoma?

A
  • Type of malignant melanoma on palms of hands and soles of feet
  • More frequent in darker-skinned people
  • Starts off flat, can develop lumps within it
32
Q

What is an amelanotic melanoma?

A
  • Type of malignant melanoma

* Lacks pigment

33
Q

What determines whether a melanoma is superficial or deep?

A
  • Less than 1mm - superficial

* More than 1mm - deep

34
Q

Why can a squamous cell carcinoma lead to the formation of a ‘horn’?

A
  • Derived from keratinocytes

* Can sometimes produce keratin

35
Q

What is a keratoacanthoma?

A

Benign lesion that looks very similar to a squamous cell carcinoma

36
Q

What causes squamous cell carcinomas?

A
  • UV exposure
  • HPV
  • Immunosuppression
37
Q

Why are the lips a common site for squamous cell carcinomas?

A
  • High sun exposure
  • Smoking and drinking
  • Good blood supply => metastasis risk
38
Q

Where is a more common sight for squamous cell carcinomas in men and women?

A
  • Men - ears (no long hair)

* Women - legs (increased exposure)

39
Q

Is the genital region a common area for squamous cell carcinoma?

A

Yes

40
Q

Can basal cell carcinoma metastasise?

A

No (but can go into fat, muscle and bone)

41
Q

Which part of the body do basal cell carcinomas commonly affect?

A

Eye lid

42
Q

What is mycosis fungoides and the stages?

A
  • Lymphomas occuring in the skin
  • Patches of erythematous, scaly skin
  • Patch stage, plaque stage and tumour stage
  • Slowly progressive
43
Q

What is Kaposi’s sarcoma?

A
  • Tumour derived from lymph endothelium
  • Related to HIV
  • Driven by HHV8
  • Looks like purple nodules on the skin
44
Q

What is epidermodysplasia veruciformis?

A
  • Predisposition of HPV induced warts and squamous cell carcinomas
  • Rare autosomal recessive condition
  • Can be covered in little, flat warts, or thick and keratotic warts
45
Q

What is the main form of treatment for skin cancers?

A

Surgical

Cancer (15 decks)

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