A 30 year-old male presented with long history of back pain and pain with ejaculation, which led to imaging studies that revealed left renal (3.5cm) and large retroperitoneal mass (6.5cm). He has a history of left undescended testicle as a child. Grossly, the kidney tumor exhibits solid and cystic cut surface on partial nephrectomy. Immunohistochemical stains show positive PAX8, GATA3 and AMACR expression in tumor cells, and negative immunoreactivity for CK7.
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1. What is the appropriate next step for definitive diagnosis of this case?
a. Immunohistochemical stain of SALL4, PLAP, OCT3/4 and AFP
b. Immunohistochemical and molecular testing for Fumarate Hydratase deficiency
c. Immunohistochemical stains of TFE3, TFEB and SDHB
d. FISH study for ETV6-NTRK3 gene fusion