Correlation between in vivo 18F-FDG PET and immunohistochemical markers of glucose uptake and metabolism in pheochromocytoma and paraganglioma.

UNLABELLED: Pheochromocytomas and paragangliomas (PPGLs) can be localized by (18)F-FDG PET. The uptake is particularly high in tumors with an underlying succinate dehydrogenase (SDH) mutation. SDHx-related PPGLs are characterized by compromised oxidative phosphorylation and a pseudohypoxic response, which mediates an increase in aerobic glycolysis, also known as the Warburg effect. The aim of this study was to explore the hypothesis that increased uptake of (18)F-FDG in SDHx-related PPGLs is reflective of increased glycolytic activity and is correlated with expression of different proteins involved in glucose uptake and metabolism through the glycolytic pathway. METHODS: Twenty-seven PPGLs collected from patients with hereditary mutations in SDHB (n = 2), SDHD (n = 3), RET (n = 5), neurofibromatosis 1 (n = 1), and myc-associated factor X (n = 1) and sporadic patients (n = 15) were investigated. Preoperative (18)F-FDG PET/CT studies were analyzed; mean and maximum standardized uptake values (SUVs) in manually drawn regions of interest were calculated. The expression of proteins involved in glucose uptake (glucose transporters types 1 and 3 [GLUT-1 and -3, respectively]), phosphorylation (hexokinases 1, 2, and 3 [HK-1, -2, and -3, respectively]), glycolysis (monocarboxylate transporter type 4 [MCT-4]), and angiogenesis (vascular endothelial growth factor [VEGF], CD34) were examined in paraffin-embedded tumor tissues using immunohistochemical staining with peroxidase-catalyzed polymerization of diaminobenzidine as a read-out. The expression was correlated with corresponding SUVs. RESULTS: Both maximum and mean SUVs for SDHx-related tumors were significantly higher than those for sporadic and other hereditary tumors (P < 0.01). The expression of HK-2 and HK-3 was significantly higher in SDHx-related PPGLs than in sporadic PPGLs (P = 0.022 and 0.025, respectively). The expression of HK-2 and VEGF was significantly higher in SDHx-related PPGLs than in other hereditary PPGLs (P = 0.039 and 0.008, respectively). No statistical differences in the expression were observed for GLUT-1, GLUT-3, and MCT-4. The percentage anti-CD 34 staining and mean vessel perimeter were significantly higher in SDHx-related PPGLs than in sporadic tumors (P = 0.050 and 0.010, respectively). Mean SUVs significantly correlated with the expression of HK-2 (P = 0.027), HK-3 (P = 0.013), VEGF (P = 0.049), and MCT-4 (P = 0.020). CONCLUSION: The activation of aerobic glycolysis in SDHx-related PPGLs is associated with increased (18)F-FDG accumulation due to accelerated glucose phosphorylation by hexokinases rather than increased expression of glucose transporters.

Endolymphatic sac tumors: clinical outcome and management in a series of 9 cases.

OBJECTIVES: Endolymphatic sac tumors (ELSTs) are rare adenomatous tumors arising in the petrous bone, either spontaneously (isolated) or in association with von Hippel-Lindau (VHL) disease. For 9 patients, this study describes the typical features and management of ELST and the clinical outcome of treatment. Similarities and differences are identified for ELST in isolation and in association with VHL disease. STUDY DESIGN: Case series. SETTING: Tertiary referral center. PATIENTS: The patient database was searched for patients diagnosed with ELST. All other tertiary referral centers in The Netherlands were invited to do likewise. INTERVENTIONS: The patient records were screened for presenting symptoms, hearing, imaging, treatment, and treatment outcome. Histopathologic finding was reviewed by a senior pathologist. RESULTS: Six patients with an isolated ELST and 3 patients with an ELST in association with VHL disease were identified. In the isolated ELST group, 5 patients were treated surgically and 1 patient was administered primary radiotherapy. In the VHL group, 1 patient underwent surgery and 2 patients were treated conservatively after a wait-and-magnetic resonance imaging-scan protocol. All individual treatment outcomes are scrupulously presented in this article. CONCLUSION: This study compiles and describes 9 cases of ELST. In 8 of 9 patients, the ELST could be controlled by surgery, radiotherapy, or a wait-and-scan protocol. The large interpatient differences make it difficult to standardize the management of this disease. The management is strongly influenced by comorbidity and tumor stage.