Cancer as a Disease: Skin Cancer

Question 1

What are the layers of the skin?

Answer 1

epidermis
dermis
hyperdermis

Question 2

What does the epidermis consist of (superficial -> deep)?

Answer 2

• Stratum corneum – dead keratinocytes
• Stratum lucidum
• Stratum granulosum
• Stratum spinosum – dendritic cells
• Stratum basale – melanocytes, merkel cells, dividing cells

Question 3

hat are the types of skin cancer?

Answer 3

• Keratinocyte derived – e.g. BCC (Basal Cell Carcinoma), SCC (Squamous Cell Carcinoma), AKA – Non-Melanoma Skin Cancer (NMSC)
• Melanocyte derived – e.g. Malignant melanoma
• Vasculature derived – e.g. Kaposi’s sarcoma, angiosarcoma
• Lymphocyte (lymphoma) derived – e.g. Mycosis fungoides

Question 4

What are some causes of skin cancer?

Answer 4

• Genetic syndromes – Gorlin’s syndrome, Xeroderma pigmentosum
• Viral infections – HHV8 (Kaposi’s sarcoma), HPV (SCC)
• UV light – BCC, SCC, malignant melanoma
• Immunosuppression – drugs, age, HIV, leukaemia

Question 5

What does a malignant melanoma look like?

Answer 5

dark coloures with an irregular margin

Question 6

What does a basal cell carcinoma look like?

Answer 6

pearly appearance and has a dilated vessel on the surface

Question 7

How do the different wave bands of UV light affect skin cancer?

Answer 7

UVA - Penetrates to deep sea level

• Major cause of skin AGEING and contributes to skin carcinogenesis.
• Also forms Cyclobutane pyrimidine dimers but less efficiently than UVB
• Forms free radicals to damage DNA and cell membranes
• Used therapeutically in PUVA therapy – treats psoriasis etc

UVB - Penetrates to ground level
- Most important in skin carcinogenesis:
> Induces direct abnormalities in skin DNA – e.g. mutations
> Induces photoproducts – affects PYRIMIDINES (C, T) bases

UVC - Does not penetrate ozone.

Question 8

What are the immunomodulatory effects of UV lihgt?

Answer 8

UVA/B effect expression of genes – deplete Langerhans cells in the epidermis -> decreased skin immunocompetance -> UV phototherapy for psoriasis BUT also further increases cancer chances

Question 9

What happens in photocarcinogenesis?

Answer 9

p53 mutations can lead to skin cancer

If p53 is intact, the cell damage will lead to expression of the p53 and repair or apoptosis of the cell

Question 10

What are the different phototypes of skin?

Answer 10

1 – always burns, never tans
2 – usually burns, sometimes tans
3 – sometimes burns, usually tans
4 – never burns, always tans
5 – moderate constitutive pigmentation – Asian
6 – moderate constitutive pigmentation – Afrocaribean

Question 11

Where is melanin produced?

Answer 11

malanocyte ( from tyrosine) within basal layer of epidemis

• Tyrosine -> DOPA -> Dopaquinone -> Eumelanin or Phaeomelanin ->

Question 12

What are the different types of melanin?

Answer 12

encoded by MCR1 gene has that has >20 polymorphisms and describes the variations in melanin

1. Eumelanin – brown or black
2. Phaeomelanin – yellowish or reddish

Question 13

What are the features of malignant melanoma?

Answer 13

• Malignant tumour of melanocytes caused by UV exposure and genetic factors
• There is a risk of metastasis

Question 14

What are the features of lentigo meligna (melanoma in situ)?

Answer 14

• Proliferation of malignant melanocytes within the epidermis
• No risk of metastasis

Features:

• Irregular shape
• Light & dark colours
• Size usually >2.0cm

Question 15

What are the features of superficial spreading malignant melanoma?

Answer 15

• Lateral proliferation of malignant melanocytes

- Invasion of the BM and a risk of metastasis

Question 16

How do you diagnose MM?

Answer 16

ABCDE:
A – Asymmetry
B – Border irregularity
C – Colour variation
D – Diameter >0.7mm and increasing
(E – Erythema)

Question 17

What are the features of nodular malignant melanoma?

Answer 17

• Vertical proliferation of MMs with no previous horizontal growth
• Risk of metastasis
• Usually much darker in appearance
• nodular melanoma arising in SSMM - Downward proliferation of MMs following previous horizontal growth - Prognosis will become worse

Question 18

What are the features of acral lentignous melanoma?

Answer 18

malignant melanoma affecting the palms and soles of the feet

Occur in darker skinned people more often than lighter coloured skin people

Question 19

What are the features of amelanotic melanoma?

Answer 19

the cancer cells have lost the ability to create melanin

Question 20

What are some risk factors for development of a melanoma?

Answer 20

• Family history
• Intermittent burning exposure
• Skin types 1, 2
• UV light exposure
• Atypical nevus syndrome
• Sunburns during childhood
• Personal melanoma history

Question 21

What are the features of squamous cell carcinoma?

Answer 21

Malignant tumour of keratinocytes

• Caused by – UV, HPV, immunosuppression, scarring processes
• Risk of metastasis
• “Horny” descriptors indicate well differentiation and the cell has retained the ability to create keratin

Question 22

What are the features of Basal-cell carcinoma?

Answer 22

• Malignant tumour arising from the basal layer of the epidermis
• Caused by – sun exposure, genetics

Features:

• Slow growing
• Invades but does not metastasise
• Common on the face

*Can be nodular or superficial

Question 23

What are the features of mycosis fungoids?

Answer 23

• Not a fungal condition – miss-classified

This is a lymphoma that affects the skin-resident T-lymphocytes
This can be fatal and has internal organ involvement

Question 24

What are the features of Kaposi’s sarcoma?

Answer 24

• HIV and HHV8 associated
• A tumour of the endothelial cells of the lymphatics
• Can occur in non-HIV patients and can occur internally

Question 25

What are the features of epidermodysplasia verruciformis?

Answer 25

Rare autosomal condition

Gives a predisposition to HPV-induced warts and SCCs