SAT-503 False-Positive 68Ga-DOTATATE PET Findings In The Evaluation Of Pheochromocytomas And Paragangliomas: A Case Series

Abstract Disclosure: S. Leblanc-Savignac: None. C. Cohade: None. F. Mercier: None. H. Olney: None. I. Bourdeau: None. Background: Functional imaging of pheochromocytomas and paragangliomas (PPGLs) using 68Ga-DOTATATE PET has shown high sensibility and specificity. However, we present three cases of suspected PPGLs that turned out to be false positives on DOTATATE PET. Clinical Cases Case 1: A 22-year-old woman known for type 1 neurofibromatosis (17q11.2 deletion) referred for a dense (100 HU), hyperintense, 43 x 31 mm, para-aortic mass found on screening MRI. She presented with occasional headaches and palpitations. DOTATATE-PET showed a left para-aortic mass with moderate uptake (SUV max 9.7). Biochemical testing was normal. With NF1 predisposing to PPGLs, typical para-aortic localization and radiological characteristics, a non-secreting PGL was suspected. The patient underwent surgery, and final pathology came back as: lymph node with histological changes compatible with Castleman disease. Case 2: A 60-year-old male known for metabolic syndrome was found with a 19 x 18 mm hyperdense heterogeneous nodule (150 HU) in the hepatorenal space on a thoracic CT scan. He presented with hot flashes and long-standing anxiety. DOTATATE PET showed strong uptake (SUV max 15.1), suggestive for PGL. Plasma free metanephrine levels were normal. Chromogranin A was slightly elevated at 106,9 ng/ml (N <82 ng/ml). Urine sampling revealed a slight increase of norepinephrine 536 nmol/d (N <475 nmol/d) and dopamine 3200 nmol/d (N <2300 nmol/d). The patient underwent surgery after alpha-blockade. Histological examination revealed a benign tumor corresponding to a hemangioma. Interestingly, exome sequencing of the hemangioma showed a pathogenic variant in the EGLN2 gene c.C1142G, p.A381G, a gene in the hypoxia induced factor 2 family associated with PPGLs and polycythemia, described for the first time in a hemangioma. Case 3: A 54-year-old man was diagnosed in 2016 with metastatic pheochromocytoma for which he underwent left adrenalectomy and nephrectomy, liver thermal ablation and radiotherapy on bone metastasis. He returned in 2023 with a lesion on the left cheek, insomnia and hypertension. DOTATATE-PET showed a 2.0 x 2.4 cm lesion in the left cheek with intense uptake (SUV max 7.1), suspicious for PPGL recurrence. Biochemical testing was normal except for elevated chromogranin A at 153,7 ng/ml (N<104 ng/ml). The patient underwent surgery after alpha-blockade. Pathology returned as high-grade B lymphoproliferative syndrome and chemotherapy was begun. Adding to the 3 presented cases, literature review showed 4 other cases of false positives with 68Ga-DOTATATE for PPGLs with the diagnoses of: solid cancer metastasis (2), focal lesion of fibrous dysplasia (1) and Castleman disease (1). Conclusion: False positive results with 68Ga-DOTATATE PET in the evaluation of PPGLs are rare but possible. A good understanding of their potential causes is essential to improve diagnostic accuracy, particularly in non-secreting tumors. Presentation: Saturday, July 12, 2025