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
Where are melanocytes found within the epidermis?
In the basal layer
What happens to melanin once it is produced by the melanocytes?
It is packaged into melanosomes and it passes along the processes of the melanocytes and is taken up by the keratinocytes
The keratinocytes put the melanosomes around their nuclei, which protects the nuclei from DNA damage
What are the two types of melanin?
Eumelanin – black/brown
Phaeomelanin – yellowish or reddish-brown
What is melanin formed from?
Tyrosine
What gene regulates the relative amounts of melanin produced?
MC1R
What is Lentigo Maligna?
Proliferation of malignant melanocytes within the epidermis
There is no risk of metastasis
This is also called melanoma in situ
What is it the name given to a large area of lentigo maligna that has a smaller area within it that has become invasive?
Lentigo maligna melanoma
What is a superficial spreading malignant melanoma?
Lateral proliferation of malignant melanocytes
They invade the basement membrane so there is a risk of metastasis
What is the ABCDE for the diagnosis of superficial spreading malignant melanoma?
Asymmetry Border irregularity Colour variation Diameter (>0.7 mm and increasing) Erythema
What is it called when a pale area appears in the middle of a melanoma?
Area of regression – this is associated with higher risk of metastasis
What is it called when you get a vertical proliferation of malignant melanocytes?
Nodular malignant melanoma
Describe the pattern of growth when a nodular melanoma arises from a superficial spreading malignant melanoma.
Downward proliferation of malignant melanocytes that is following previous horizontal growth
What is the type of melanoma that occurs on the palms and soles?
Acral lentiginous melanoma
What type of melanoma produced no melanin?
Amelanotic melanoma
What is the prognosis of melanoma based on?
Breslow thickness – thickness from the top of the tumour to the bottom
What is a keratoacanthoma?
It is either a benign lesion or a benign version of an SCC
It grows rapidly but then disappears
There is no risk of metastasis
What can squamous cell carcinomas (SCCs) be caused by?
UV exposure
HPV
Immunosuppression (main cancer in organ transplant patients)
How can you tell whether an SCC is well differentiated?
If the lesion has a keratin horn then it shows that the keratinocytes can still produce keratin and so they are well differentiated
What is a basal cell carcinoma (BCC)?
Malignant tumour arising from keratinocytes in the basal layer of theepidermis
Describe the appearance of BCCs
They are pearly, have a rolled edge and often have arborising telangiectasia
Name a cutaneous T cell lymphoma.
Mycosis fungoides
Which viruses are associated with Kaposi sarcoma?
HHV8
HIV
Name a disease that predisposes to SCCs and HPV induced warts (that can become incredibly keratotic).
Epidermodysplasia Veruciformis
