LBSAT65 Search For A Duplicitous Pheochromocytoma

INTRODUCTION: Pheochromocytomas are discovered during work up of adrenal incidentalomas and can be biochemically and clinically silent. We present a case of a patient who presented with typical "adrenergic spells" suggestive of pheochromocytoma but negative biochemical testing and non-confirmatory imaging findings. CASE REPORT: 39-year-old male presented with 4 weeks history of episodes of throbbing headaches, palpitations, sweating. He was found to be hypertensive, blood pressure of 220/110 mm Hg. Losartan was initiated, but symptoms persisted. Work-up for endocrine causes of hypertension revealed normal plasma renin activity 1.123 ng/ml/hr (0.167 to 5.380) and undetectable aldosterone level <1 ng/dl (0. 0-3. 0), mildly elevated random plasma normetanephrine 270 pg/ml (0-210), normal plasma metanephrines 49 pg/ml (0-88). Low-dose dexamethasone suppression test showed unsuppressed morning cortisol of 2.1ug/dl, undetectable ACTH <5 pg/ml, dexamethasone level 486 ng/dl. 24 urinary cortisol and 2 midnight salivary cortisol samples failed to confirm the diagnosis. 24-hr urine studies showed mildly elevated 24-hr normetanephrine 735 ug/24 hr (156-729), normal 24-hr metanephrines 197 ug/L (58-276), normal 24 hr epinephrine and dopamine levels. Repeat testing revealed normal plasma metanephrines levels and mildly elevated plasma normetanephrine levels 287 pg/ml (less than twice above the upper limit of normal). Dopamine and Chromogranin A levels were undetectable. Abdominal CT showed 2 cm round soft tissue density 42HU in right adrenal gland. Left adrenal gland contained 3 nodules measuring 11, 15 and 16 mm–all with density <10HU. MRI findings for the 2.2 cm right adrenal nodule was without significant drop in signal intensity on the in and out of phase sequences appearing moderately T2 hyperintense and T1 hypointense. Differential included atypical/fat poor adenoma, pheochromocytoma, or metastasis. On GA 68 Dotatate PET-CT this 2.2cm adrenal nodule had minimal to low radiotracer uptake. Since a pheochromocytoma could not be ruled out, patient was started on alpha blockade. Preoperative genetic testing was negative for common mutations associated with pheochromocytoma/paraganglioma syndromes. Patient underwent laparoscopic right adrenalectomy. Histopathology report confirmed 2.8 cm pheochromocytoma with a low PASS (2/20) and low GAPP score. CONCLUSION AND DISCUSSION: Patients with borderline nor metanephrine elevations represent a diagnostic and therapeutic dilemma. The patient presented with adrenergic paroxysms strongly suggestive of underlying pheochromocytoma. Labs and imaging were not typical for pheochromocytoma and were indeterminate. Given strong clinical suspicion for a pheochromocytoma, we decided to proceed with adrenalectomy after pre-treatment with alpha blockers. Final histopathologic report confirmed the diagnosis of pheochromocytoma. Presentation: Saturday, June 11, 2022 1:00 p.m. - 3:00 p.m.