All samples were reviewed by a genitourinary pathologist (Y.B.C.) to confirm diagnosis. Immunohistochemistry for FH and 2-succino-cysteine (2SC) [FH loss and/or 2SC gain] was performed in 5-mm FFPE tissue sections where tissue was available. Immunohistochemistry for FH was performed using a mouse monoclonal antibody (clone J-13, Santa Cruz Biotechnology) as previously described.(21 (link)) An absence of FH staining in the neoplastic cells, in the presence of positive internal control (cytoplasmic, granular staining in non-neoplastic cells), was interpreted as lost or FH-deficient status. Immunohistochemical staining for S-(2-succino)-cysteine (2SC) was performed using a polyclonal antibody described previously.(10 (link), 22 (link)) Briefly, 4-μm-thick sections from representative formalin-fixed, paraffin-embedded tissue blocks were processed using the Ventana Discovery XT system with antigen retrieval (CC1 solution, 60 min), primary antibody (1:2000), and OptiView DAB IHC detection steps (Ventana). The presence of diffuse, nuclear and cytoplasmic staining was interpreted as positive.