Succinate Dehydrogenase-Deficient Renal Cell Carcinoma.

Succinate dehydrogenase (SDH)-deficient renal cell carcinoma is a recently recognized distinct subtype of renal cell carcinoma in the 2016 World Health Organization classification. It is associated with gene germline mutations, which also cause paraganglioma/pheochromocytoma, gastrointestinal stromal tumor, and pituitary adenoma. The tumor most commonly presents in young adulthood. The tumors are arranged in solid nests or in tubules and frequently show cystic change. The tumors are composed of cuboidal to oval cells with round nuclei, dispersed chromatin, and inconspicuous nucleoli. The cytoplasm is eosinophilic or flocculent but not truly oncocytic. The most distinctive histologic feature is the presence of cytoplasmic vacuoles or inclusions. Loss of SDH subunit B immunostaining is needed for a definite diagnosis. The prognosis is good for low-grade tumors but worse for tumors with high-grade nuclei, sarcomatoid change, or coagulative necrosis. Long-term follow-up is indicated.