Cancer 15: Cancer as a disease - Skin cancer Flashcards
Describe the skin microanatomy
See slide - 3 layers
- Epidermis (most skin cancers arise from this layer)
- Dermis
- Hypodermis
Describe the structure of the epidermis
Keratinocytes - start at the basement membrane. Develop (differentiate) and lose their nucleus as they move up. They are become dead at the top - stratum corneum.
Melanocytes - produce melanin
Merkle cells - sensation
Langerhans cells - antigen presenting cells
List the types of skin cancer
Keratinocyte derived
- basal cell carcinoma
- squamous cell carcinoma
Non melanoma skin cancer (NMSC)
Melanocyte derived
- Malignant melanoma
Vasculature derived
- Kaposi’s sarcoma, angiosarcoma
Lymphocyte derived
- Mycosis fungoides
Describe the basic causes of skin cancer
1) Accumulation of genetic mutations
2) Uncontrolled cell proliferation
Gives some examples of different causes of skin cancer?
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
Describe the epidemiology of skin cancer?
Malignant melanoma = incidence increases in white the population
Basal cell carcinoma = incidence in increasing in men and women
Describe the ultraviolet spectrum
See diagram
UVC - 100-280
UVB - 280-310
UVA - 310-400
Describe UVB light?
most important wavelength in skin carcinogenesis
UVB directly induces abnormalities in DNA eg mutations
UVB induces photoproducts (mutations)
- Affects pyrimidines ie Cytosine (C) and Thymine (T) bases
1) cyclobutane pyrimidine dimers eg T=T, T=C, C=C
2) 6-4 pyrimidine pyrimidone photoproducts - Usually repaired quickly by nucleotide excision repair
Describe UVA light?
- 100 times more UVA penetrates to the Earth’s surface
- major cause of skin ageing
- contributes to skin carcinogenesis
- used therapeutically in PUVA therapy
