Incidental Succinate Dehydrogenase (SDH) Deficient Renal Cell Carcinoma and Paraganglioma in a 24-Year-Old

Abstract

Abstract Introduction/Objective Succinate dehydrogenase (SDH)-deficient renal cell carcinoma (RCC) is rare neoplasm (<0.2% of all RCCs) caused by SDH-subunit gene mutation, usually SDHB. Patients carrying such mutations are also predisposed to other SDH-deficient neoplasms such as paraganglioma, gastrointestinal stromal tumor, and pituitary adenoma. Here, we report a case of incidental SDH-deficient RCC and paraganglioma. Methods/Case Report A 24-year-old male without past medical or family history presented to ED for perianal abscess. Imaging showed 8-cm heterogeneous left renal mass (figure-A) and 3.3-cm mass below aortic bifurcation, highly concerning for RCC with metastasis. Biopsy of kidney mass showed nested and trabecular epithelial neoplasm with weakly eosinophilic and occasionally vacuolated cytoplasm (figure-B). Nuclei were round with smooth contour and inconspicuous nucleoli. Tumor was immunopositive for PAX8, e-cadherin, P504S, and CD10, while negative for CK7, CD117, and Melan-A. SDHB immunostain was negative in tumor with intact staining in intervening endothelium. Findings were consistent with SDH-deficient RCC. Biopsy of pelvic mass showed low-grade neoplasm that was immunopositive for synaptophysin, chromogranin, and GATA3, with S100-positive sustentacular cells, consistent with paraganglioma. Patient underwent radical nephrectomy which revealed 7.5-cm, well-circumscribed, tan-red, predominantly solid mass with few cysts. Histologically, tumor had thin fibrous capsule and morphologically similar to biopsy. Tumor was limited to kidney without necrosis, sarcomatoid/rhabdoid differentiation, or vascular invasion. Results (if a Case Study enter NA) NA. Conclusion SDH-deficient RCC is rare low-grade entity with risk of metastasis and development of other neoplasms, which requires continued follow-up and potential genetic testing for patient and family members. Therefore, including SDH-deficient RCC in differential diagnosis of eosinophilic renal neoplasms is essential.