Neoplasia USMLE Step 1 Practice Question
A 52-year-old woman with a history of cutaneous melanoma (Breslow thickness 2.4 mm, Clark level IV) resected from her left shoulder 8 years ago presents with progressive left axillary swelling over the past 2 months. She denies constitutional symptoms. Vital signs are stable. Physical examination reveals a single, firm, 2-cm pigmented lymph node in the left axilla; no other lymphadenopathy or hepatosplenomegaly is appreciated. Fine-needle aspiration of the axillary node shows pigmented cells with increased nuclear-to-cytoplasmic ratio and prominent nucleoli consistent with metastatic melanoma. Laboratory studies show LDH 480 U/L (normal <250). Staging imaging reveals no distant metastases beyond the regional lymph node. Which of the following cellular properties best accounts for the characteristic pattern of regional and distant lymph node involvement seen in melanoma?
Answer choices
- ADownregulation of E-cadherin and upregulation of vimentin, promoting epithelial-mesenchymal transition and lymphatic invasionCorrect answer
- BConstitutive activation of BRAF-V600E with increased mitotic activity and tumor cell proliferation
- CEnhanced expression of neural crest cell markers (c-KIT, SOX10) that confer inherent migratory capacity
- DUpregulation of MHC class I molecules preventing recognition by cytotoxic T lymphocytes during transit
- ERestoration of telomerase activity enabling unlimited replicative potential in transit metastases
- FLoss of melanin synthesis reducing visible tumor burden and enabling occult lymphatic spread
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