SDH-deficient renal cell carcinoma with intracytoplasmic mucinous material: a case report and literature review.

Succinate dehydrogenase (SDH)-deficient renal cell carcinoma (RCC) is a rare, molecularly defined neoplasm. We report a 45-year-old man with a right renal mass treated by nephrectomy. Grossly, a 38-mm gray-white-to-brown solid cystic tumor was observed in the lower pole of the kidney. Microscopically, the tumor consisted of sheets and nested proliferation of eosinophilic cells with low-grade nuclei and bubbly or flocculent cytoplasm. No sarcomatoid or rhabdoid features were observed. Abundant extracellular and focal intracytoplasmic mucinous material was observed in the tumor, which was positive for Alcian blue and mucicarmine staining, but negative for periodic acid-Schiff staining. Immunohistochemistry showed complete loss of succinate dehydrogenase subunit B in tumor cells. These findings supported the diagnosis of RCC consistent with SDH-deficient RCC. This case expands the morphological spectrum of SDH-deficient RCC and highlights the diagnostic pitfalls of renal tumors with mucinous material.