Cancer as a Disease – Skin Cancer Flashcards
What are the five layers of the epidermis?
Stratum corneum Stracum lucidum Stratum granulosum Stratum spinosum Stratum basale
What are the main cell types in the epidermis?
Keratinocytes
Melanocyts
Langerhans Cells
Merkel Cells
State the types of skin cancer that come under each of the following types:
a. Keratinocyte derived
b. Melanocyte derived
c. Vasculature derived
d. Lymphocyte derived
a. Keratinocyte derived Basal Cell Carcinoma Squamous Cell Carcinoma b. Melanocyte derived Malignant Melanoma c. Vasculature derived Kaposi Sarcoma – endothelium of lymphatics Angiosarcoma – endothelium of blood vessels d. Lymphocyte derived Mycosis fungoides
State two examples of genetic syndromes that massively increase the risk of getting skin cancer.
Gorlin’s Syndrome – regular BCCs
Xeroderma Pigmentosum – increased risk of BCC, SCC and malignant melanoma
Give two examples of viruses that can lead to skin cancer?
HHV8
HIV
What is the difference between the depth reached by UVB radiation and UVA radiation?
UVB – reaches sea level
UVA – reaches dead sea leve
How does UVB cause mutations in DNA?
Induces the formation of photoproducts
Particularly affects pyrimidines – causing cross-linking
Formation of cyclobutane pyrimidine dimers and 6-4 pyrimidine pyrimidone photoproducts
How are these mutations usually corrected?
Nucleotide excision repair
How can UVA promote skin carcinogenesis?
Forms cyclobutane pyrimidine dimers (but less effectively than UVB)
Also generates free radicals that can damage DNA
Name a condition that is caused by a defect in nucleotide excision repair.
Xeroderma pigementosum
What are the features of this condition?
Increased risk of BCCs, SCCs and melanoma
Photosensitivity and dry skin
What happens to keratinocytes in sunburn?
The UV damage leads to keratinocyte apoptosis
The apoptotic cells in UV overexposed skin are called sun burn cells
Describe the immunomodulatory effects of UV light.
UVA and UVB affect the expression of genes involved in skin immunity
It depletes Langerhans cells in the epidermis
This reduces skin immunocompetence and immunosurveillance
What are the consequences of UV therapy for psoriasis?
Increased risk of skin cancer UV can act on keratinocytes and cause DNA damage
If the Langerhans cells have been depleted then they will be unable to knock out the damaged cells so they could persist and become cancerous
Which system is used to categorise people based on their skin type and sensitivity to UV?
Fitzpatrick Phenotypes