Solid pseudopapillary tumour should be part of differential diagnosis of focal pancreatic lesions with increased 18 F‐FDOPA uptake

François Somme (1) , Marie‐soline Montaz‐rosset (1) , Gerlinde Averous (2) , Jeanne Deur (2) , Bernard Goichot (3) , Philippe Bachellier (4) , Pietro Addeo (4) , Alessio Imperiale (5, 1)

1 ICANS - Institut de Cancérologie de Strasbourg Europe
2 Hôpitaux Universitaires de Strasbourg
3 Service de Médecine Interne, Endocrinologie et Nutrition [CHU Strasbourg]
4 Pôle des Pathologies Digestives Hépatiques et Transplantation [Hôpital Hautepierre-Strasbourg]
5 DRHIM-IPHC - Département de Radiobiologie, Hadronthérapie et Imagerie Moléculaire

Objective To assess the specificity of increased 18F‐dihydroxyphenylalanine (18F‐FDOPA) uptake in patients who underwent PET/CT for suspicion of isolated pancreatic neuroendocrine tumour (pNET). False‐positive results mimicking a pNET have been investigated. Material and methods Carbidopa‐assisted 18F‐FDOPA PET/CT scans performed in patients with suspicion of localized pNET were retrieved. Only patients with a definitive diagnosis were retrospectively included. When available, the histopathological result after pancreatic surgery was the gold standard. In other cases, the diagnosis was based on endoscopic ultrasonography (EUS)/cytology and/or on concordant imaging results of at least two of the following: contrast‐enhanced computed tomography (CE‐CT), magnetic resonance imaging (MRI) and somatostatin receptor scintigraphy (SRS). Results Forty‐four among 731 patients were selected. Among these, 36 patients (82%) were surgically treated, revealing pNET (n = 28), solid pseudopapillary tumour (SPT) (n = 4), adenocarcinoma (n = 2), serous cystadenomas (n = 1) and solitary fibrous tumour (n = 1) cases. An additional three cases of pNET were diagnosed by EUS/cytology. In the remaining five patients, a consensus was reached on follow‐up imaging results: pNET (n = 1), serous cystadenoma (n = 2) and undetermined/no pNET (n = 2). Both specificity and negative predictive value of 18F‐FDOPA PET/CT for localized pNET were 67%. Surprisingly, all four false‐positive results were SPTs showing intense 18F‐FDOPA uptake and negative SRS. There was no significant difference in 18F‐FDOPA uptake intensity between PET‐positive pNETs and SPTs. Conclusion 18F‐FDOPA PET/CT is not specific for pNET in patients with localized pancreatic lesions. SPT could mimic pNET and should be part of differential diagnosis in such a clinical situation. If these results are confirmed in a broader population, the imaging pattern 18F‐FDOPA PET‐positive/SRS‐negative lesions might be considered as the imaging phenotype of SPT.

Domaines: Sciences du Vivant [q-bio]

François Somme, Marie‐soline Montaz‐rosset, Gerlinde Averous, Jeanne Deur, Bernard Goichot, et al.. Solid pseudopapillary tumour should be part of differential diagnosis of focal pancreatic lesions with increased 18 F‐FDOPA uptake. Clinical Endocrinology, 2020, ⟨10.1111/cen.14202⟩. ⟨hal-02573694⟩