Skin Cancer

Question 1

What is the main Epidemiological agent of Skin cancer ?

Name some others

Answer 1

The main aetiological agent is sunlight

others include: ionising radiation, viruses, tissue scarring

Question 2

What are the main types of Skin Cancer, list them with decreasing incidence.

What is the correlation with aggressivness?

Answer 2

Incidence:

1. Basal cell carcinoma is the highest
2. Squamous cell carcinoma
3. Melanoma is the lowest

Aggressiveness increases with decreasing incidence

Question 3

What are the different Fitzpatrick phenotypes, which one is the most vulnurable?

Which populations are of higher risk?

Answer 3

Fitzpatrick phenotypes:

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

• Commoner in Fitzpatrick skin type I
  
  • Sun sensitive skin!
• More common in those who live closer to the equator, and work outside

Question 4

What are the different UV light frequences?

Which are the most dangerous?

Answer 4

UV-A; 310-400nm

• 100 times more of this will reach the surface than UV-B, it is the major cause of ageing but it will also contribute to carcinogenesis.
  
  • It results free radical generation, it mostly performs damage through T>G transversions, membrane damage.

UV-B: 280-310nm

• Most important wavelength in carcinogenesis
• Forms pyrimidine dimers (e.g. thymine dimers)–> adjacent thymidine residues are covalently
  
  • Specific examples include cylobutane butane dimers, 6-4 pyrmidine pyrimidine photoproducts – these are more mutagenic but are repaired much quicker.

UVC

• 100-280nm
• This is filtered out by the ozone

The higher the wave length, the closer it is to the visible spectrum, and the lower the carcinogenicity, the lower the wave length the closer it is to X rays and the higher its carcinogenicity.

Question 5

Which are the effects of the UV light?

Answer 5

P53:

• A tumour suppressor gene coded for by 17q
• Sensitive to UV damage – One mutated p53 is enough to have a mutagenic effect
• Binds to DNA as a tetramer, regulating many different genes

Langerhans cells:

• Immune cells which detect tumour associated antigens and present them to T cells, resulting in destruction of the tumour
• Sensitive to UV damage, density decreases with exposure.

Question 6

What are the features of a Basal cell carcinoma (Age group, metastasis, formation, appearance)

Answer 6

1. Elderly – most commonly seen on head and neck (sun exposure)
2. Arises from epidermal stem cells
3. Locally destructive
4. NOT METASTATIC
5. Pearly appearance with telangiectasia

Question 7

What are the main features of a squamous cell carcinoma? (Age, metastasis state, appearance, areas, origin)

Answer 7

• Malignancy of epidermal keratinocytes of the skin.
• Sun exposed areas like head and neck – main rf is UV rad
  
  • Other rfs inc HPV
• ELDERLY
• METASTATIC – spreads to regional lymph nodes then organs (esp lungs)
• may be ulcerated, hyperkeratotic (with keratin horn), crusted or scaly, non-healing

Question 8

What are the main features of Melanoma? (origin, age, metastasis, risk factors)

Answer 8

• Tumours which arise from melanocytes
• Highly metastatic, spreading to regional lymph nodes–> solid organs (lungs, liver & brain).
• Can also affect younger pts
• Risk factors
  
  1. Dysplastic naevae (moles)
  2. Family history
  3. Tanning beds
  4. Intermittent, intense, early age sun exposure.

Question 9

Epidermodysplasia Verruciformis

Answer 9

• Autosomal recessive
• “treeman syndrome”
• Mild immunodeficiency results in multiple viral warts (of HPV), and these go on to become oncogenic in sun exposed keratinocytes that are infected
• E6 protein of HPV deactivates p53
• Results in squamous cell carcinoma.