6365 An Atypical Case Of Large Metastatic Pheochromocytoma With Negative Catecholamine Secretion

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Abstract Disclosure: D. Caesario: None. J.K. Fernandes: None. Introduction: Pheochromocytomas (PCCs) are rare tumors arising from chromaffin cells of the adrenal medulla. Diagnosis is suggested by clinical presentations and confirmed by biochemical hypersecretion of metanephrines (MN) and catecholamines (CA). We report an atypical case of large metastatic PCC with normal MN and CA. Case Report: A 61-year-old female presented with uncontrolled HTN despite taking amlodipine, losartan, and carvedilol. No other symptoms reported. She had presented 12 years prior with an 8.7 cm left adrenal mass (AdM) that was incidentally found on CT scan, but she was lost to follow-up. Repeat imaging for her current presentation revealed enlargement of left AdM to 15 cm, centrally necrotic, with absolute washout of 63%. There was extensive local regional involvement, including possible invasion of the pancreas; abutment to left kidney, left renal vein, left hepatic lobe, and stomach; encasement and possible invasion of the splenic vein; and formation of perisplenic collateral vessels. Metastatic lesions were also seen in the liver, bones, and lungs. DOTATATE PET/CT scan showed variable uptake, not a definitive pattern for PCC or neuroendocrine tumor (NET). Labs showed normal levels of plasma fractionated MN and CA, dopamine, renin, aldosterone, cortisol, ACTH, and DHEA-S. Chromogranin A (CgA) was elevated to >8000 ng/dL. Biopsy taken from one of the liver lesions was consistent with metastatic PCC. No family history of NET. Genetic testing was offered, but was deferred. Due to the large tumor burden, she was determined to be nonsurgical and started on systemic therapy with sunitinib. Doxazosin was also added, which better controlled her BP. After 9 months of sunitinib therapy, a repeat CT scan showed overall stable metastatic lesions, but the left AdM had enlarged to 16 cm. Given the slowly worsening disease, patient was switched to temozolomide. She is still actively being treated and monitored today. Discussion: The clinical features of PCC result from excessive CA secretion. HTN is the hallmark of CA release, but the amount, type, and pattern of CA secretion is extremely variable, leading to varied clinical presentations. CgA secretion is also elevated in PCC, but is generally a non-specific marker as its level is also increased in multiple NETs and non-endocrine medical conditions. About 9% of patients with PCC may have normal biochemical workup, with this being even rarer in malignant cases. In general, the amount of CA, MN, and CgA released by the tumor is also positively correlated with the tumor size. The case above is unique in that despite the large tumor burden the patient only presented with HTN and had normal MN and CA levels. Her CgA was significantly elevated, which could correlate with the tumor size, but was interestingly the only marker elevated. It appears that CgA could be a useful adjunct in the diagnosis of PCC, especially in cases where PCC appeared to be non-secretory. Presentation: 6/3/2024