PSAT011 Biochemically Silent Pheochromocytoma in an Asymptomatic Patient with a Unilateral Lipid Poor Adrenal Adenoma

INTRODUCTION: Pheochromocytomas are rare catecholamine-secreting tumors arising from the adrenal medulla, which can occur in asymptomatic patients. Diagnosis is primarily through biochemical evidence of catecholamine over secretion, however, in rare cases catecholamine levels are within normal limits. These are known as "biochemically silent" pheochromocytoma. The lack of biochemical evidence makes diagnosis particularly challenging in cases presenting as adrenal incidentalomas. We present a patient with a left adrenal incidentaloma, initially identified 10 years ago which has been slowly growing and gradually becoming biochemically active. This case illustrates how radiologic findings can alert providers to the presence of pheochromocytoma and the importance of not immediately attributing mild biochemical abnormalities to medications. CASE: A 50-year-old Caucasian female presented to the clinic for evaluation of a left adrenal incidentaloma discovered 10 years ago. Past medical history is significant for hypothyroidism, dyslipidemia, anxiety and depression. Patient had undergone surveillance of the adrenal nodule both radiographically and biochemically since its discovery. First available imaging is a CT Abdomen/Pelvis in 2016 that noted a 1.7cm left adrenal nodule with unenhanced attenuation value of 25.6 HU. Most recent CT Abdomen/Pelvis in June 2021 reported a 2.6cm mixed density enhancing left adrenal gland nodule with less apparent macroscopic fat, concerning for a lipid poor adenoma. Biochemical work up done previously was reported to be non-functional. In 2018, elevated 24-hr urine normetanephrine of 859mcg/24h (88-649mcg/24h) and elevated 24-hr urine total metanephrines of 955mcg/24h (182-739mcg/24h) were noted. No intervention was done at that time. In August 2021, elevated plasma normetanephrine of 308.6 pg/ml (0-136.8pg/ml), elevated urine 24hr norepinephrine of 165mcg/24h (0-135mcg/24h), and elevated urine 24 hr urine normetanephrine of 1015mcg/24h (131-612mcg/24h) were noted. Rest of the biochemical work up was negative for hyperaldosteronism, hypercortisolemia and hyperandrogenemia. Although elevations were noted in the above values, they were <2 fold and the patient was also taking Effexor which can falsely elevate the normetanephrine levels. However, given the increasing size of the lipid poor adenoma, the patient was referred for endocrine surgery evaluation. She was preoperatively placed on doxazosin and underwent laparoscopic surgical removal. Pathology was consistent with a 2.4cm pheochromocytoma. Postoperatively, plasma metanephrines and normetanephrines were within normal limits. Subjectively, patient reports improvement of her hot flashes, insomnia and anxiety. CONCLUSION: This case emphasizes the importance of surveillance for a lipid poor adrenal nodule. Providers should have a high level of suspicion for pheochromocytoma in patients with a lipid poor adenoma even if they are biochemically silent. A knowledge of medications causing falsely elevated catecholamine levels is necessary, however, these should be considered along with other clinical and radiological findings. Early diagnosis is important, if pheochromocytoma remains unrecognized it can lead to high morbidity and mortality. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.