Neoplasia USMLE Step 1 Practice Question
A 59-year-old woman presents with right upper quadrant pain, weight loss, and jaundice. Vital signs show BP 128/82, HR 92, RR 16, Temp 37.2°C, SpO2 98%. CT abdomen reveals a 4-cm heterogeneous liver mass with elevated transaminases (AST 187 U/L). Liver biopsy demonstrates nests of atypical epithelial cells without lymphoid aggregates. Which immunohistochemical stain would best differentiate carcinoma from sarcoma or lymphoma in this metastatic malignancy of unknown primary?
Answer choices
- AGlial fibrillary acidic protein
- BCytokeratinCorrect answer
- CDesmin
- DCD31
- EVimentin
- FS-100 protein
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