Notably, in a re-appraisal series of 33 cases diagnosed originally as so-called ‘unclassified’ RCC in patients aged 35 years or younger, 22 of 33 (66%) were reclassified as eosinophilic-solid and -cystic RCCs, FH-deficient RCCs, and succinate dehydrogenase-deficient RCCs [100]. The gene discussed is FH; the disease is renal cell carcinoma.