Current views on imaging of adrenal tumors

High prevalence of adrenal cortical adenomas in patients with cerebral meningiomas

PURPOSE

Adrenal cortical adenomas (ACAs) represent one of the most common endocrine neoplasms. Recently, a genetic syndrome, characterized by tumor-suppressor ARMC5-gene mutations and causing primary macronodular bilateral adrenal hyperplasia with concomitant meningiomas of the central nervous system, has been described. Apart from this rare disorder and despite the well-known influence of steroid hormones on meningiomas, no data are available about the association between ACAs and meningiomas.

METHODS

We investigated the prevalence of ACAs in a group of patients with cerebral meningioma undergoing unenhanced chest CT scans before attending surgical treatment. Patients with meningioma were age- and sex-matched in a 1:3 ratio with hospitalized patients for COVID-19.

RESULTS

Fifty-six patients with meningioma were included and matched with 168 control patients with COVID-19. One-hundred forty-four (66.1%) were female and the median age was 63 years. Twenty ACAs were detected in the overall population (8.9% of the subjects): 10 in patients with meningioma (18%) and the remaining 10 (6%) in the control group (p = 0.007). Multivariate analysis showed that age and presence of meningioma were statistically associated with the presence of ACAs (p = 0.01, p = 0.008).

CONCLUSION

We report, for the first time, a higher prevalence of ACAs in patients with meningioma as compared to age- and sex-matched controls. Larger studies are needed to confirm our data and to clarify the characteristics of the ACAs in patients with meningioma. Whether the detection of ACAs should prompt a neuroimaging evaluation to exclude the presence of meningiomas needs also to be considered.

Can Quantification of VMAT and SSTR Expression Be Helpful for Planning Radionuclide Therapy of Malignant Pheochromocytomas?

Tumor-specific uptake of the radio-iodinated norepinephrine analogue meta-iodobenzylguanidine (MIBG) or uptake of radiolabeled somatostatin analogues via somatostatin receptors (SSTRs) are possibilities to diagnose and treat malignant pheochromocytomas/paragangliomas (PCs/PGs). The aims of this study were to investigate the quantitative expression of vesicular monoamine transporters (VMAT 1, 2) and all five SSTRs in malignant pheochromocytoma/paraganglioma (PC/PG) to evaluate the possibilities for tumor-specific radionuclide therapy. High scintigraphic 123I-MIBG uptake was found in two malignant PGs with high VMAT expression (500-730 copies of VMAT 1, 1,500-1,700 copies of VMAT 2 per 1,000 beta-actin), while no 123I-MIBG uptake was found in the malignant PG with low VMAT expression (330 copies of VMAT 1, 350 copies of VMAT 2 per 1,000 beta-actin). The two patients with high VMAT expression and high 123I-MIBG uptake were treated with 131I-MIBG (2-3x8 GBq). In vitro, the VMAT antagonist, reserpine, and the membrane pump inhibitor, clomipramine, inhibited the uptake of 123I-MIBG into tumor cells equally well (48% and 53% reduction respectively, P<0.001). SSTR2 was the most abundant receptor subtype, but in the two malignant PGs its expression was only 110-260 copies/1,000 beta-actin. The transporters at the cell membrane and in the vesicular membrane both appear to be of importance for the uptake of 123I-MIBG into malignant PC/PG. Quantitative determination of VMAT expression may be helpful in selecting patients suitable for radionuclide therapy with 131I-MIBG. The present data indicate that SSTR-mediated radionuclide therapy will not be effective treatment of malignant PC/PG.

Catecholamine-Secreting Metastatic Carcinoid as Differential Diagnosis in Pheochromocytoma: Clinical, Laboratory, and Imaging Clues in the Search for the Lurking Neuroendocrine Tumor (NET)

Catecholamine-secreting metastatic carcinoid should be considered in differential diagnosis of malignant pheochromocytoma. Paroxysmal functioning or hormonally silent gastroenteropancreatic neuroendocrine tumors (GEP NETs) require repeat biochemical measurements and sensitive anatomic and functional imaging studies overlapping those for malignant pheochromocytoma. This report presents clinical, laboratory, and radiologic findings in a patient presenting with heart rate variability; vasoactive headaches reactive to ethanol, tyramine and tryptophan; labile blood pressure; diaphoresis; diarrhea; abdominal pain; unexplained pancreatitis; joint pain; and paroxysmal flushing with pallor. GI studies (including endoscopic ultrasound) and multiple imaging modalities (including 2D CT, MRI with gadolinium, [18]FDG PET/CT, [123I]MIBG, and SRS [111In]Octreotide [OctreoScan]) were not diagnostic. 24-h BP, Holter and 30-day cardiac event monitors plus urinary biochemical studies consistently suggested catecholamine-synthesizing NET. NIH plasma metanephrines studies and [6]-[18F]Fluorodopamine PET ruled out malignant pheochromocytoma (pheo). Repeated studies showed persistently abnormal GEP NET biomarkers and urinary catecholamines. Capsule endoscopy revealed suspicious submucosal lesions throughout the small intestine. Dual-phase 64-slice multidetector computed tomography (MDCT) with 3D volumetric reconstruction of the abdomen and pelvis revealed multiple diffuse liver metastases and three extrahepatic lesions consistent with metastatic carcinoid. In combination, intensive biochemical testing repeated over time, dual-phase 64-slice MDCT with 3D image reconstruction and volume-rendering (VR) technique, and advanced radionuclide imaging are required to detect NETs' sporadic or paroxysmal functioning, rule out extra-adrenal pheochromocytoma, and localize and characterize metastatic carcinoid. If pheochromocytoma is ruled out, yet symptoms and biochemical markers for catecholamine excess are present, then carcinoid and other amine-precursor-uptake decarboxylation (APUD) tumors must remain in the differential diagnosis.