Fig. 6: FH deficient RCC with low grade oncocytic histology.

Fumarate hydratase-deficient low-grade oncocytic renal cell carcinoma (A) may closely resemble an SDH-deficient tumor. However, SDHB is retained in the tumor cells, whereas FH is completely lost. Diffuse nuclear and cytoplasmic positivity for 2SC in the tumor (B); this immunohistochemical stain is considered to be more sensitive than FH in these tumors.