Photobiology and skin cancer

Question 1

UV A vs B

Answer 1

A is aging, B is burning. Both cause cancer, though B is what does direct damage to DNA (thymine dimers). A mostly damages via ROS production

Question 2

Actinic (senile) purpura

Answer 2

easy bruising due to shattering of blood vessels due to collagen loss from UVA exposure

Question 3

BCC: gross appearance, classic location, histology

Answer 3

pink, pearl like papule. Surrounded by telangectasias. Upper lip. Nodules of basal cells w/ peripheral palisading

Question 4

BCC: what is the common mutation? prognosis?

Answer 4

PTCH (tumor suppressor). Mets are rare, most common type of skin cancer.

Question 5

Appearance of SCC compared to BCC. Location?

Answer 5

less pearly, more scaly. Sun exposed areas esp. LOWER lip

Question 6

Actinic keratosis. Mutation in?

Answer 6

premalignant lesions. Transform into SCC. Rough and scale. p53 mutation

Question 7

Xeroderma pigmentosum: defect, risk

Answer 7

defect in nucleotide excision repair genes. Risk of skin cancer.

Question 8

Nevoid basal cell carcinoma sydrome: defect, affect, risk

Answer 8

mutation in PTCH gene so sonic hedgehog pathway goes unregulated. Risk for BCC

Question 9

Oculocutaneous albinism

Answer 9

Normal # melanocytes, no melanin.

Question 10

SPF: what does it address? how does rating work?

Answer 10

UVB protection. # of times longer to reach minimal erythematous dose (MED)