6.

Serial sections of an FH-deficient RCC stained with A) H&E, B) fumarate hydratase, and C) 2SC immunohistochemistry. A) In this case the neoplastic cells have prominent nucleoli but lack the typical papillary or tubulocystic-like architecture of more readily recognized FH-deficient RCC. B) FH immunohistochemistry shows negative staining in all neoplastic cells that contrasts with the positive granular cytoplasmic (mitochondrial) staining in the internal positive controls. C) 2SC immunohistochemistry is positive in a nuclear and cytoplasmic pattern in all the neoplastic cells.