Metanephrine Negative Pheochromocytoma: A rare case report of dopamine-secreting tumor in an adolescent patient with NF1.

Pheochromocytoma (PCC) occurs in 4% of pediatric neurofibromatosis type 1 (NF1) patients and is mostly characterized by epinephrine and norepinephrine secretion. Herein, we report the first case of a dopamine-secreting PCC in a 13-year-old patient with NF1, in whom a left adrenal mass was incidentally found on abdominal computed tomography (CT) during hypertension workup. Fractionated 24-h urine metanephrine excretion was normal but urine dopamine level was elevated. On 123I-metaiodobenzylguanidine (MIBG) single photon emission tomography/CT (SPECT/CT), focal MIBG uptake was observed. Our multidisciplinary team determined that surgery would be difficult to perform because the tumor was small and the symptoms were vague, with only increased dopamine level. After six months, the tumor increased in size on abdominal CT, with focal significant uptake of the lesion on 6-[18F]fluoro-L-3,4-dihydroxyphenylalanine (18F-FDOPA) PET/CT. Laparoscopic resection was performed, and the mass was histologically confirmed as PCC. Currently, the vital signs of the patient are stable, urine dopamine levels are normal, and there is no abnormal uptake of 18F-FDOPA PET/CT. This study reports a case of a rare dopamine-secreting PCC. When metanephrine is negative in patients at high risk of PCC, focused examination and multidisciplinary approach are needed.