LAUSR

Abstract Disclosure: D. Madhavarapu: None. R. Kaufman: None. G. Kim: None. Pheochromocytomas are rare neuroendocrine tumors with an annual incidence of 0.8 per 100,000 person-years and can be asymptomatic in up to 25% of cases. Genetic factors, particularly SDHB mutation, play a significant role, occurring in 5% of sporadic cases and 9-33% of familial cases. This case report describes a 61-year-old female with a history of colon cancer who was incidentally found to have a 2.6 x 1.6 cm right adrenal nodule and a 2.7 x 3.1 x 2.5 cm left renal mass during follow-up imaging. The left renal mass was determined to be clear cell renal cell carcinoma. Prior to considering a biopsy of the right adrenal nodule to assess for potential metastasis from the renal cell carcinoma, a biochemical workup was performed to rule out pheochromocytoma. The patient was asymptomatic, and the biochemical evaluation was normal, allowing for the adrenal biopsy to proceed safely. Unexpectedly, the biopsy revealed pheochromocytoma, and subsequent immunohistochemical staining confirmed an SDHB mutation, associated with high malignancy potential. Approximately 34% to 70% of SDHB-mutated pheochromocytomas are considered to have high malignant potential, with a 35-75% risk of metastasis. The presence of an SDHB mutation in a non-secretory, asymptomatic pheochromocytoma is exceptionally rare and clinically significant. Additionally, the patient was diagnosed with clear cell renal cell carcinoma following left nephrectomy sparing left adrenal gland. She is currently scheduled for right adrenalectomy. This case underscores the importance of comprehensive genetic and pathological evaluation in managing adrenal incidentalomas, particularly when clinical and biochemical presentations are atypical. It highlights the potential for SDHB-mutated pheochromocytomas to be non-secretory while still carrying a high risk of malignancy, emphasizing the need for vigilant follow-up and management strategies in such cases. Presentation: Sunday, July 13, 2025