Skin Cancer Pathology and Oncology Flashcards

What is the Breslow depth, and why is it the most important prognostic factor in primary melanoma?

Answer: Tumor thickness measured in mm from the granular layer to deepest tumor cell; predicts metastatic risk and survival

Breslow depth is the vertical tumor thickness in millimeters measured by pathology, directly correlating with 5-year survival — thicker melanomas have greater access to lymphatics and blood vessels for metastasis.

Which sunscreen ingredient provides the broadest UVA protection and is commonly used in US formulations?

Answer: Avobenzone (Parsol 1789)

Avobenzone is the only FDA-approved organic UV filter providing full UVA protection (320–400 nm) but requires photostabilizers (like octocrylene) as it degrades with UV exposure.

Dermatofibrosarcoma protuberans (DFSP) is characterized by which genetic translocation?

Answer: t(17;22) resulting in COL1A1-PDGFB fusion gene

DFSP carries a translocation t(17;22) fusing COL1A1 and PDGFB, resulting in constitutive PDGF receptor activation, which is also the rationale for treating with imatinib (Gleevec).

Which actinic keratosis feature suggests highest risk of progression to invasive SCC?

Answer: Hypertrophic/thick AK with induration and tenderness

Hypertrophic, indurated, or tender actinic keratoses have the highest risk of harboring or progressing to invasive SCC and warrant aggressive treatment or biopsy.

What is the mechanism by which UV radiation causes DNA damage leading to skin cancer?

Answer: Formation of cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts in DNA

UVB radiation causes direct DNA damage by inducing formation of cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts between adjacent pyrimidine bases, causing characteristic C→T mutations.

Which type of non-melanoma skin cancer is most commonly seen in organ transplant recipients on long-term immunosuppression?

Answer: Squamous cell carcinoma (SCC)

Immunosuppressed transplant recipients develop SCC at dramatically higher rates (65–250 times higher) than the general population, with SCC outnumbering BCC — the reverse of the normal ratio.