Cancer as a Disease – Skin Cancer Flashcards
What are the five layers of the epidermis?
Stratum corneum Stratum lucidum Stratum granulosum Stratum spinosum Stratum basale
What are the 4 main cell types in the epidermis?
Keratinocytes
Melanocytes
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
Keratinocyte: Basal + Squamous Cell Carcinoma
Melanocyte: Malignant Melanoma
Vasculature: Kaposi Sarcoma, Angiosarcoma
Lymphocyte: 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 + malignant melanoma
Give two examples of viruses that can lead to skin cancer?
HHV8
HPV
What is the difference between the depth reached by UVB radiation and UVA radiation?
UVB – reaches sea level
UVA – reaches dead sea level
How does UVB cause mutations in DNA?
Induces formation of photoproducts (mutations)
Causing cross-linking of pyrimidines
E.g. Cyclobutane pyrimidine dimers (T=T, T=C, C=C)
6-4 pyrimidine pyrimidone photoproducts
How are UVB 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 happens to keratinocytes in sunburn?
UV induced apoptosis- removes damaged cells with cancerous potential
Apoptotic cells in UV overexposed skin= sun burn cells
Describe the immunomodulatory effects of UV light.
UVA + UVB affect expression of genes involved in skin immunity
Deplete Langerhans cells in the epidermis
Reduces skin immunocompetence + immunosurveillance
What are the consequences of UV therapy for psoriasis?
Increased risk of skin cancer
UV can act on keratinocytes + cause DNA damage
If Langerhans cells have been depleted, they will be unable to knock out damaged cells so they could persist + become cancerous
Which system is used to categorise people based on their skin type and sensitivity to UV?
Fitzpatrick Phenotypes (I-VI)
Where are melanocytes found within the epidermis?
In the basal layer - Stratum basale
What happens to melanin once it is produced by the melanocytes?
Packaged into melanosomes, passes along processes of melanocytes + is taken up by keratinocytes
Keratinocytes put 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? What ratio depends on this?
MCR1
Eumelanin : Phaemomelanin produced
What is Lentigo Maligna?
Proliferation of malignant melanocytes within the epidermis
“Pagetoid” spread- melanocytes have spread up
No risk of metastasis
AKA. 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
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 + increasing) Erythema
What is it called when a pale area appears in the middle of a melanoma? What is this associated with?
Area of regression: associated with higher risk of metastasis
What is it called when you get a vertical proliferation of malignant melanocytes with no previous horizontal growth? What is the consequence of this?
Nodular malignant melanoma
Risk of metastasis
Describe the pattern of growth when a nodular melanoma arises from a superficial spreading malignant melanoma.
Downward proliferation of malignant melanocytes following previous horizontal growth
What type of melanoma 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 top of tumour to bottom
What is a keratoacanthoma?
A benign lesion or a benign version of an SCC
Grows rapidly but then disappears
No risk of metastasis
What can squamous cell carcinomas (SCCs) be caused by?
UV exposure
HPV
Immunosuppression
Scarring process
How can you tell whether an SCC is well differentiated?
If lesion has a keratin horn, it shows the keratinocytes can still produce keratin , thus are well differentiated
What is a basal cell carcinoma (BCC)?
Malignant tumour arising from keratinocytes in the basal layer of the epidermis
Describe the appearance of BCCs
Pearly- greyish, shiny, glistens
Rolled edge
Arborising telangiectasia
Pinky/ red/ grey
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
Describe 4 features of BCC’s
Caused by sun exposure + genetics
Slow growing
Invades tissue but doesn’t metastasise
Common on face
What is a squamous cell carcinoma (SCC)?
Malignant tumour of keratinocytes
Has risk of metastasis (though much smaller risk than melanoma)
What are the 4 overarching causes of skin cancer?
Genetic syndromes
Viral infections
UV light
Immunosuppression
Describe the incidence rates of malignant melanoma and basal cell carcinoma?
MM: Increasing, mainly in white skinned people
BCC: Increasing
Describe 4 visual characteristics of malignant melanomas
Dark
Red border
Lumpy
Abnormal appearance
What does skin colour depend on?
Amount + type of melanin produced
not the density of melanocytes
Describe 3 features of Malignant melanomas
Malignant tumour of melanocytes
Caused by UV exposure + genetic factors
Risk of metastasis
Describe the appearance of Lentigo Maligna
Irregular shape
Light + dark brown
Usually > 2cm
List 4 key risk factors for development of melanomas
PMH of melanoma
FH of melanoma
Skin type 1 or 2
Sunburns during childhood
What is the main approach to treatment in skin cancer?
Surgery
