Cancer as a Disease - Skin Cancer Flashcards
4 TYPES OF SKIN CANCER?
- Keratinocyte derived:
- Melanocyte derived
- Vasculature derived
- Lymphocyte derived
e.g. of keratinocyte derived skin cancer? (2)
Basal cell carcinoma (BCC) (most common skin cancers)
Squamous cell carcinoma (SCC)
e.g. of Melanocyte derived skin cancer?
Malignant melanoma
e.g. of Vasculature derived skin cancer? (2)
Kaposi’s sarcoma – derived from the endothelial cells of the lymphatics (common in HIV)
Angiosarcoma – derived from endothelial cells of blood vessels
e.g. of Lymphocyte derived skin cancer?
Mycosis fungoides
4 causes of skin cancer?
Genetic conditions, viral infection, UV light and immunosuppression
What genetic conditions can cause skin cancer?
Xeroderma Pigmentosum
why is the incidence of BCC increeasing
Ageing population
What type of UV is more significant in carcinogenesis
UVB
which is the most penetrating uv radiation
UVA
How does UV cause DNA damage
Affects pyrimidines ie Cytosine (C) and Thymine (T) bases, forms Cyclobutane pyrimidine dimers e.g. T=T, T=C, C=C and 6-4 pyrimidine pyrimidone photoproducts
What process usually repairs UV DNA damage
nucleotide excision repair
how does xeroderma pigmentosum cause skin cancer
defective Nucleotide Excision Repair
3 ways mutations can cause cancer?
- Mutations that stimulate uncontrolled cell proliferation e.g. abolishing control of the normal cell cycle (p53 gene)
- Mutations that alter responses to growth stimulating / repressing factors
- Mutations that inhibit programmed cell death (apoptosis)
What are sunburn cells
Sun burn’ cells are apoptotic cells in UV overexposed skin
- Apoptosis removes UV damaged cells in the skin which might otherwise become cancer cells
What protein regulates to see if DNA is too damaged for skin cancer
p53
What immunomodulatory effects does UV have
UVA and B deputed langerhans cells which reduces skin immunocompetence and immunosurveillance and increases cancer causing potential
Fitzpatrick phenotypes?
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 - Asian
VI - Marked constitutive pigmentation – Afro-Caribbean
Basically, pale skin = burns, darker skin = doesn’t burn
What does skin colour depend on
amount and type of melanin produced
how does UV cause melanin production
Dendritic processes on the melanocytes communicate with the keratinocytes
Under UV light, the keratinocyte will make more MSH and this will have a paracrine effect on the melanocyte to make more melanin
This is packaged etc. and used by keratinocytes to protect the nucleus from DNA damage
2 types of melanin? which type is more common in whiteos
- Eumelanin – brown or black This is the one that pigments the skin
- Phaeomelanin – yellowish or reddish brown Pale people have more of this type
What amino acid is used to form melanin
tyrosine
What gene controls melanin
MCR1
What explains different hair and skin colours
The polymorphism of MCR1
What is a MALIGNANT MELANOMA:
Malignant tumour of the melanocytes
- Melanocytes become abnormal
- Atypical cells and architecture
Causes of malignant melanoma
- UV exposure
- Genetic factors
Risk of metastasising?
Possible
What is LENTIGO MALIGNA
MELANOMA IN SITU) Proliferation of malignant melanocytes within (and restricted to) the epidermis – no risk of metastasis as they haven’t penetrated the basement membrane
what is invasion within a lentigo maligna known as
lentigo maligna melanoma
SUPERFICIAL SPREADING MALIGNANT MELANOMA risk of metastasising?
there is an increased risk as there is usually invasion of the basement membrane
What is the ABCDE rule in melanomas
Asymmetry Border irregular Colour variation (dark brown-black) Diameter >0.7mm and increasing Erythema – losing of ability to make melanin in part of the tumour
What is a nodular malignant melanoma
Vertical proliferation of malignant melanocytes with no previous horizontal growth, there is a risk of metastasis
What is a superficial spreading malignant melanoma
Lateral proliferation of malignant melanocytes, invasion through the basement membrane, risk of metastasis
What is a NODULAR MALIGNANT MELANOMA ARISING WITHIN A SUPERFICIAL SPREADING MALIGNANT MELANOMA
Downward proliferation of malignant melanocytes following previous horizontal growth
- Nodule developing within irregular plaque
- Prognosis will become worse
What is a acral lentiginous melanoma
Occur on the sole of the foot – these are the ones that occur in darker skinned individuals
What is amelanotic melanoma
Melanoma lacking the ability to make melanin
What is the prognosis of melanomas dependent on
Related to the thickness of the melanoma from the top of the lesion to the botton (in mm) Called BRESLOW THICKNESS
- Less than 1mm = superficial
- More than 1mm = deeper = higher risk of metastasis
What is Breslows thickness
Melanomas relation of the prognosis to the thickness of the melanoma from the top of the lesion to the botton
Risk factors of melanomas?
family history UV exposure sunburns intermittent burning exposure skin type 1 and 2 history of melanoma
What is SQUAMOUS CELL CARCINOMA:
Malignant tumour of keratinocytes
What causes SQUAMOUS CELL CARCINOMA:
- UV exposure
- HPV
- Immunosuppression
- May occur in scars or scarring processes
risk of metastasis of SQUAMOUS CELL CARCINOMA?
Risk
Male high risk sites of SQUAMOUS CELL CARCINOMA:
ears, lips, genitals
Female high risk sites of SQUAMOUS CELL CARCINOMA:
legs
What is Keratoacanthoma
benign tumour that can look like SCC
what is basal cell carcinoma
Malignant tumour arising from basal layer of epidermis
Risk of metastasis of basal cell carcinoma?
No risk
Causes of basal cell carcinoma
- Sun exposure
- Genetics
Common area for a basal cell carcinoma?
face
What is mycosis fungoides
If a lymphocyte restricted to tissue becomes cancerous and causes lymphoma in the skin it is called mycosis fungoides
Presentation of mycosis fungoides
plaques and patches of erythematous scaley skin
Metastasis risk of mycosis fungoides?
Metastasises but is slowly progressing
What is Kaposis sarcoma
Tumour derived from lymph endothelium
What drives Kaposis sarcoma
HHV8 virus
What is EPIDERMODYSPLASIA VERUCIFORMIS
Rare autosomal recessive condition with a predisposition to HPV induced warts and SCCs (think India elephant man)
