SAT-310 18F-FDOPA PET/CT Accurately Identifies Pheochromocytoma in 70-Year-Old Male with MEN1

Abstract

18F-FDOPA PET/CT accurately identifies pheochromocytoma in 70-year-old male with MEN1 Background: Multiple endocrine neoplasia type 1 (MEN1) is an autosomal dominant inherited disorder that causes tumors most often in the parathyroid, pancreas, and pituitary. Pheochromocytoma in MEN1 is extremely rare (< 2% of cases). Identifying tumor functionality by imaging is challenging given the multiplicity of tumors in MEN1. Case Report: We are reporting a case of a 75-year old male first diagnosed at age 60 with MEN1. Sequencing of MEN1 revealed the pathogenic variant c.249_252delGTCT causing a frameshift mutation. At the time of diagnosis, he was found to have mild hyperparathyroidism status post 2-gland resection, non-functional pituitary microadenoma and bilateral adrenal masses (2.6 cm left; 2.4 cm right). The patient was normotensive and asymptomatic, with elevated plasma normetanephrine 114 pg/mL (upper limit of normal 112) and metanephrine 148 pg/mL (upper limit of normal 61). The remainder of his biochemical workup at that time was normal. The patient remained normotensive and asymptomatic, and routine yearly CT evaluation demonstrated growth of the left adrenal mass to 3.9 cm (9 Hounsfield unit (HU) pre-contrast, and post-contrast HU of 15), and right adrenal mass to 2.6 cm. Follow-up biochemical evaluation revealed an adrenergic biochemical phenotype with elevated plasma metanephrine 432 (12-61 pg/ml) and normetanephrine 291 (18-112 pg/ml) levels, with normal norepinephrine 198 (84-794 pg/ml), dopamine <25 (0-25 pg/ml) but elevated epinephrine 126 (0-57 pg/ml) levels. FDG-PET/CT demonstrated bilateral adrenal uptake (6.36 SUV on the left, and 4.38 SUV on the right) and I-123-MIBG scintigraphy demonstrated abnormal uptake of tracer corresponding to both adrenal masses. However, 18F-FDOPA PET/CT demonstrated a centrally photopenic left adrenal mass (28.7 SUV) and physiologic 18F-FDOPA PET uptake on the right adrenal mass. 68Ga-DOTATATE was not available at the time. The patient underwent an uneventful left adrenalectomy for pheochromocytoma in June 2016 and has had normalization of his previously elevated biochemical results. Loss of heterozygosity at 11q13 was analyzed and determined to be positive. Conclusion: Pheochromocytoma in MEN1 is extremely rare. Despite a lack of symptoms, enlarging adrenal nodules should be screened for pheochromocytoma. Particularly in the setting of elevated plasma metanephrines and undetermined adrenal masses by anatomic imaging, FDG-PET/CT and/or I-123-MIBG, 18F-FDOPA PET/CT may be beneficial.