ABD Cutaneous Oncology 2 — Questions and Answers
Question 1: Which histologic subtype of basal cell carcinoma carries the highest risk of subclinical extension and local recurrence?
- Nodular
- Superficial
- Infiltrative/morpheaform (Correct answer)
- Pigmented
Correct answer: Infiltrative/morpheaform
Infiltrative and morpheaform BCCs have aggressive growth patterns with poorly defined margins and high recurrence risk.
Question 2: A 62-year-old man has a 2.5 cm squamous cell carcinoma on the ear with perineural invasion. Which feature most upgrades his risk?
- Tumor location on the ear
- Perineural invasion of a nerve ≥0.1 mm
- Size over 2 cm
- All contribute but PNI of large nerves is key high-risk (Correct answer)
Correct answer: All contribute but PNI of large nerves is key high-risk
Large-caliber perineural invasion, ear location, and size >2 cm are all high-risk features, with large-nerve PNI being especially adverse.
Question 3: The Breslow depth is measured from which anatomic landmark?
- Top of the granular layer to deepest tumor cell (Correct answer)
- Basement membrane to deepest tumor cell
- Stratum corneum to base of tumor
- Dermal-subcutaneous junction upward
Correct answer: Top of the granular layer to deepest tumor cell
Breslow thickness is measured from the top of the granular layer to the deepest invasive melanoma cell.
Question 4: Which immunostain is most useful to confirm melanocytic differentiation in a spindle-cell (desmoplastic) melanoma?
- HMB-45
- Melan-A
- S100 (Correct answer)
- Cytokeratin AE1/AE3
Correct answer: S100
Desmoplastic melanoma is often HMB-45 and Melan-A negative but reliably S100 positive.
Question 5: For melanoma, sentinel lymph node biopsy is generally recommended starting at what Breslow thickness (with no other high-risk features)?
- 0.5 mm
- 0.8 mm (Correct answer)
- 1.0 mm
- 2.0 mm
Correct answer: 0.8 mm
SLNB is considered for melanomas ≥0.8 mm or thinner lesions with ulceration.
Question 6: A hedgehog pathway inhibitor such as vismodegib is FDA-approved for which malignancy?
- Metastatic melanoma
- Locally advanced or metastatic basal cell carcinoma (Correct answer)
- Cutaneous T-cell lymphoma
- Merkel cell carcinoma
Correct answer: Locally advanced or metastatic basal cell carcinoma
Vismodegib targets the SMO component of the hedgehog pathway driving advanced BCC.
Question 7: Which recurrent gene fusion is characteristic of dermatofibrosarcoma protuberans?
- EWSR1-FLI1
- COL1A1-PDGFB (Correct answer)
- PAX3-FOXO1
- BRAF-KIAA1549
Correct answer: COL1A1-PDGFB
DFSP is driven by the COL1A1-PDGFB fusion, making imatinib effective in advanced disease.
ABD Cutaneous Oncology 2
Which histologic subtype of basal cell carcinoma carries the highest risk of subclinical extension and local recurrence?