FDG PET/CT Scan and Functional Adrenal Tumors: A Pilot Study for Lateralization

Subtyping of Cushing's Syndrome: A Step Ahead

Cushing's Syndrome (CS) is a rare disease due to chronic endogenous cortisol secretion. In recent years, new developments have broadened the spectrum of differential diagnosis, traditionally categorized as adrenocorticotropic hormone (ACTH)-dependent and ACTH-independent forms. Moreover, increased awareness of the detrimental effects of cortisol on cardiometabolic health and the risk of cardiovascular events lead to increased diagnosis of mild forms, especially in the context of adrenal incidentalomas.This review provides an up-to-date narrative of the most recent literature regarding the challenges of CS diagnosis. After the description of the diagnostic tools available, the functional non-neoplastic hypercortisolism (formerly known as pseudo-Cushing state) is characterized, followed by the subtyping of the different conditions of hypercortisolism, including the differential diagnosis of ACTH-dependent forms and the management of adrenal hypercortisolism, with peculiar attention to the new genetic classification of adrenal CS, mild autonomous cortisol secretion, and bilateral adrenal adenomas.

False-Positive Metastatic Disease Due to Bilateral Ectopic Adrenal Tissue

ABSTRACT

A 60-year-old man was referred for staging of prostate cancer. Initial CT scan demonstrated soft tissue lesions in bilateral renal hila, which demonstrated mild 68 Ga-PSMA avidity and moderate FDG avidity on sequential PET scans suspicious for malignancy. Biopsy confirmed adrenal cortical tissue. This case highlights an exceedingly rare occurrence of ectopic adrenocortical tissue in both renal hila.

Role of adrenal venous sampling in the differential diagnosis and treatment protocol of ACTH-independent Cushing's syndrome with bilateral adrenal lesions

PURPOSE

The diagnosis and management of adrenocorticotropic hormone-independent Cushing's syndrome (AICS) with bilateral adrenal lesions remain challenging. Some studies have explored the value of adrenal vein sampling (AVS) in patients with AICS; however, more investigations are needed to assess its benefits for diagnosis and treatment planning in this population.

METHODS

Thirteen patients with clinical, biochemical and imaging evidence of AICS with bilateral adrenal lesions underwent AVS in our department from 2017-2022 were recruited. Only the data from nine patients for whom AVS succeeded were finally included in this study and further analyzed. Blood samples were successfully collected from both adrenal veins (AV) and inferior vena cava (IVC) in these nine patients, and the levels of plasma total cortisol (PTC) and plasma aldosterone concentrations (PAC) were measured. The ratio of the PAC of the AV to the IVC was calculated, and the PTC to PAC ratios were compared between AV. The surgical strategy was chosen according to the results of AVS. Postoperative histology and immunohistochemistry of the adrenal tissues were performed. The prognosis was evaluated based on the improvement of clinical symptoms and biochemical parameters (including PTC and ACTH measurements).

RESULTS

Patients with AICS were clinically diagnosed based on clinical signs, results of functional tests and the presence of bilateral adrenal lesions as observed on computed tomography imaging. An AV to IVC PAC ratio greater than 2 confirmed successful AVS. The PTC to PAC ratio (high side to low side) was greater than 2 in four patients, and less than 2 in five patients. The postoperative pathological results were consistent with clinical diagnosis and AVS. During the mean follow-up of 33 months, all nine patients achieved varying degrees of clinical improvement.

CONCLUSION

Our study showed that AVS helped to distinguish unilateral and bilateral lesions, identify the laterality of the autonomous hypercortisolism, and improve therapeutic strategy selection in patients with AICS and bilateral adrenal lesions.

Clinical, pathophysiologic, genetic and therapeutic progress in Primary Bilateral Macronodular Adrenal Hyperplasia

Patients with primary bilateral macronodular adrenal hyperplasia (PBMAH) usually present bilateral benign adrenocortical macronodules at imaging and variable levels of cortisol excess. PBMAH is a rare cause of primary overt Cushing's syndrome, but may represent up to one third of bilateral adrenal incidentalomas with evidence of cortisol excess. The increased steroidogenesis in PBMAH is often regulated by various G-protein coupled receptors aberrantly expressed in PBMAH tissues; some receptor ligands are ectopically produced in PBMAH tissues creating aberrant autocrine/paracrine regulation of steroidogenesis. The bilateral nature of PBMAH and familial aggregation, led to the identification of germline heterozygous inactivating mutations of the ARMC5 gene, in 20-25% of the apparent sporadic cases and more frequently in familial cases; ARMC5 mutations/pathogenic variants can be associated with meningiomas. More recently, combined germline mutations/pathogenic variants and somatic events inactivating the KDM1A gene were specifically identified in patients affected by GIP-dependent PBMAH. Functional studies demonstrated that inactivation of KDM1A leads to GIP-receptor (GIPR) overexpression and over or down-regulation of other GPCRs. Genetic analysis is now available for early detection of family members of index cases with PBMAH carrying identified germline pathogenic variants. Detailed biochemical, imaging, and co-morbidities assessment of the nature and severity of PBMAH is essential for its management. Treatment is reserved for patients with overt or mild cortisol/aldosterone or other steroid excesses taking in account co-morbidities. It previously relied on bilateral adrenalectomy; however recent studies tend to favor unilateral adrenalectomy, or less frequently, medical treatment with cortisol synthesis inhibitors or specific blockers of aberrant GPCR.

ACTH-independent production of 11-oxygenated androgens and glucocorticoids in an adrenocortical adenoma

SIGNIFICANCE STATEMENT

Due to its rarity, biochemical and histologic characteristics of androgen and glucocorticoid co-secreting adrenocortical adenomas are largely unknown. Herein, we report a case of adrenocortical adenoma that caused marked hyperandrogenemia and mild autonomous cortisol secretion. In this study, we investigated serum steroid profiles using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and histologic characteristics of the resected tumor. LC-MS/MS revealed highly elevated levels of 11-oxygenated androgens which have not been well studied in adrenal tumors. The expression patterns of steroidogenic enzymes determined by immunohistochemistry supported the results of steroid profiling and suggested the capacity of the tumor cells to produce 11-oxygenated androgens. Measurement of 11-oxygenated steroids should facilitate a better understanding of androgen-producing adrenocortical neoplasms.

18F-FDG-PET/CT Evaluation of Indeterminate Adrenal Masses in Noncancer Patients

CONTEXT

Adrenal tumors in noncancer patients are common.

OBJECTIVE

Evaluate performance of 18F-fluorodeoxyglucose positron emission tomography computed tomography (18F-FDG-PET/CT) in distinguishing between benign and malignant adrenal tumors.

DESIGN

Retrospective chart review 2010-2019.

SETTING

Academic institution.

PATIENTS

One hundred and seventeen noncancer patients, defined as having no history of cancer or with cancer in remission for ≥5 years, completed 18F-FDG-PET/CT to evaluate adrenal masses, with pathologic diagnoses or imaging follow-up (≥12 months).

INTERVENTION

18F-FDG-PET/CT of 117 indeterminate adrenal masses.

MAIN OUTCOME MEASURES

Receiver operator characteristic curve of the ratios of adrenal lesion standardized uptake value (SUV)max to liver SUVmean and of adrenal lesion SUVmax to aortic arch blood pool SUVmean were constructed.

RESULTS

Seventy benign and 47 malignant masses (35 adrenocortical carcinomas [ACCs], 12 adrenal metastases) were identified. Malignant masses had higher median liver SUV and blood pool SUV ratios than benign masses (6.2 and 7.4 vs 1.4 and 2.0, P < .001). Median liver and blood pool SUV ratios of ACC (6.1 and 7.3, respectively) and metastases (6.7 and 7.7, respectively) were higher than those of than adenomas (1.4 and 2.2, P < .05 for all comparisons). Optimal liver SUV ratio to discern between benign and malignant masses was 2.5, yielding 85% sensitivity, 90% specificity, and 7 false negative results (including 3 ACCs). Optimal blood pool SUV ratio was 3.4, yielding 83% sensitivity, 90% specificity, and 8 false negative results (including 4 ACCs).

CONCLUSION

When used in conjunction with other clinical assessments, 18F-FDG-PET/CT can be a valuable tool in evaluating adrenal masses in noncancer patients.

Adrenal Vein Cortisol to Metanephrine Ratio for Localizing ACTH-Independent Cortisol-Producing Adenoma: A Case Report

Context

Finding the source of adrenocorticotropic hormone (ACTH)-independent cortisol-producing adenoma in the patients with subclinical Cushing syndrome (SCS) and bilateral adrenal nodules is sometimes challenging. Computed tomography (CT) and positron emission tomography are helpful, but adrenal venous sampling (AVS) is the gold standard approach. However, interpretation of AVS is important to improve the accuracy of decision-making for surgery. We report a case and review of the literature to assess the benefit of using adrenal vein cortisol to metanephrine ratio to determine the source of cortisol production in SCS and bilateral nodules.

Evidence Acquisition

Three authors searched PubMed for data on patients with SCS who had AVS procedure and measurements of cortisol and catecholamines.

Case Description

A 51-year-old woman with SCS and hypertension crisis presented to our clinic. Paraclinical investigations revealed that she had an ACTH-independent cortisol-producing adenoma and her CT scan showed bilateral adrenal nodules. After AVS, cortisol (high to low) lateralization ratio could not determine the source of cortisol production but the cortisol to metanephrine ratio localized the source to the left side, which included the larger nodule according to CT measurements. Left adrenalectomy led to clinical and paraclinical improvement.

Conclusion

There is a possibility of co-secretion of other steroids accompanied with cortisol in the setting of ACTH-independent SCS. Moreover, cortisol measurement alone and interpretation of AVS results based on cortisol values may not help lateralizing the source of cortisol production with bilateral adrenal nodules. Therefore, we suggest applying cortisol to metanephrine ratio with the same gradient (gradient > 2.3, highest to lowest concentration) when the source of cortisol production cannot be determined by cortisol lateralization ratio.

Hypoxia-induced modulation of glucose transporter expression impacts 18F-fluorodeoxyglucose PET-CT imaging in hepatocellular carcinoma

PURPOSE

To investigate the molecular mechanisms underlying the variable standard uptake value (SUV) of ¹⁸F-fluorodeoxyglucose positron emission tomography-computed tomography (¹⁸F-FDG PET-CT) imaging in hepatocellular carcinoma (HCC) and whether hypoxia-induced glucose transporter expression contributes to the progression of HCC and the rate of glycolysis in HCC cells.

MATERIALS AND METHODS

Sixteen HCC specimens obtained from patients who underwent pre-treatment staging with ¹⁸F-FDG PET-CT imaging were divided into high maximum SUV (SUV_max > 8) and low SUV_max (SUV_max < 5) groups and employed for whole-genome gene expression profiling using GeneChip Human Genome U133 Plus 2.0 Arrays. The relationship between SUV_max and the expression of glucose transporters 1 and 3 (GLUT1 and GLUT3) was further validated using immunohistochemical analysis. The expression of GLUT1 and GLUT3 in different HCC cells under hypoxia and normoxia conditions were monitored by quantitative reverse transcription PCR (RT-qPCR). Glycolysis and FDG uptake by HCC cells were measured using the Seahorse XF glycolysis stress test and ¹⁸F-FDG PET-CT imaging. The effect of GLUT1 and GLUT3 on glucose uptake in HCC cells was examined using the fluorescent D-glucose analog 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl) amino]-2-deoxy-d-glucose (2-NBDG) followed by detection of fluorescence produced by the cells using flow cytometry.

RESULTS

Glucose transporters are differentially expressed between samples from HCC patients with high and low SUV_max. In particular, over-expression of GLUT1 and GLUT3 in high SUV_max patients was correlated with high glucose uptake and overall survival. The expression of GLUT1 and GLUT3 was significantly induced by hypoxia in different HCC cells. High expression of GLUT1 and GLUT3 in HCC cells were correlated with high rates of glycolysis and 18F-FDG uptake. Therefore, our data suggested that hypoxia-induced glucose transporters expression could result in the variations of ¹⁸F-FDG PET-CT imaging and progression of HCC, contributing to more aggressive disease phenotypes like large tumor size, recurrence, and poor survival.

CONCLUSION

Over-expression of GLUT1 and GLUT3 significantly increase glucose uptake in HCC cells. Hypoxia-induced glucose transporters expression may therefore be a contributing variable in ¹⁸F-FDG PET-CT imaging and progression in HCC.

Diagnostic efficacy of 18F-FDG PET/CT in patients with adrenal incidentaloma

BACKGROUND

The management of adrenal incidentaloma is still a challenge with respect to determining its functionality (hormone secretion) and malignancy. In this light, we performed 18F-FDG PET/CT scan to assess the SUVmax values in different adrenal masses including Cushing syndrome, pheochromocytoma, primary hyperaldosteronism and non-functional adrenal adenomas.

METHODS

Total 109 (73 F, 36 M) patients with adrenal mass (incidentaloma), mean age of 53.3 ± 10.2 years (range, 24-70) were screened by 18F-FDG PET/CT. Data of 18F-FDG PET/CT imaging of the patients were assessed by the same specialist. Adrenal masses were identified according to the calculated standardized uptake values (SUVs). Clinical examination, 24-h urine cortisol, catecholamine metabolites, 1-mg dexamethasone suppression test, aldosterone/renin ratio and serum electrolytes were analyzed.

RESULTS

Based on the clinical and hormonal evaluations, there were 100 patients with non-functional adrenal mass, four with cortisol-secreting, four with pheochromocytomas and one with aldosterone-secreting adenoma. Mean adrenal mass diameter of 109 patients was 2.1 ± 4.3 (range, 1-6.5 cm). The 18F-FDG PET/CT imaging of the patients revealed that lower SUVmax values were found in non-functional adrenal masses (SUVmax 3.2) when compared to the functional adrenal masses including four with cortisol-secreting adenoma (SUVmax 10.1); four with pheochromcytoma (SUVmax 8.7) and one with aldosterone-secreting adenomas (SUVmax 3.30). Cortisol-secreting (Cushing syndrome) adrenal masses showed the highest SUVmax value (10.1), and a cut-off SUVmax of 4.135 was found with an 84.6% sensitivity and 75.6% specificity cortisol-secreting adrenal adenoma.

CONCLUSIONS

Consistent with the similar studies, non-functional adrenal adenomas typically do not show increased FDG uptake and a certain form of functional adenoma could present various FDG uptake in FDG PET/CT. Especially functional adrenal adenomas (cortisol secreting was the highest) showed increased FDG uptake in comparison to the non-functional adrenal masses. Therefore, setting a specific SUVmax value in the differentiation of malignant adrenal lesion from the benign one is risky and further studies, including a high number of functional adrenal mass are needed.

Outcomes of Adrenal Venous Sampling in Patients with Bilateral Adrenal Masses and ACTH-Independent Cushing's Syndrome

BACKGROUND

Management of patients with bilateral adrenal masses and ACTH-independent Cushing's syndrome (AICS) is challenging, as bilateral adrenalectomy can lead to steroid dependence and lifelong risk of adrenal crisis. Adrenal venous sampling (AVS) has been previously reported to facilitate lateralization for guiding adrenalectomy. The aim of the current study was to investigate the utility of AVS using protocol from study by Young et al. in the management of patients with bilateral adrenal masses and AICS.

METHODS AND DESIGN

A retrospective review of all patients with bilateral adrenal masses and AICS who underwent AVS from 2008 to 2016 was performed. AVS for cortisol and epinephrine was performed with dexamethasone suppression. The adrenal vein to peripheral vein cortisol ratios and side-to-side cortisol lateralization ratios were calculated.

RESULTS

AVS was successful in 8 of 9 patients. All 8 patients had AVS results indicating bilateral cortisol hypersecretion. Six patients underwent adrenalectomy: 3 had unilateral adrenalectomy of the larger size mass, 2 had bilateral adrenalectomy (both sides >4 cm.) and 1 had stepwise bilateral adrenalectomy. Final pathology revealed macronodular adrenal hyperplasia in all 6 patients that underwent surgery.

CONCLUSION

AVS was useful in excluding a unilateral adenoma as the source of AICS in this study of patients with bilateral adrenal masses and AICS. However, adrenal mass size influenced surgical decision making more than AVS results. More data are needed before AVS can be advocated as essential for management of patients with bilateral adrenal masses and AICS.

Characterization of adrenocortical tumors by 18F-FDG PET/CT: Does steroid hormone hypersecretion status modify the uptake pattern?

BACKGROUND

adrenal tumor-to-liver uptake value (Tmx:Lmx) on ¹⁸F-FDG PET/CT is an accurate and reproducible PET parameter in the distinction between benign and malignant adrenal masses. The potential impact of steroid hormone secretion on ¹⁸F-FDG uptake is still debatable. The aim of this study was to evaluate this relationship.

METHODS

2010-2015: 73 patients who underwent adrenalectomy for adrenocortical tumors [49 secreting/(SA) and 24 non-secreting/(NSA)] were retrospectively included in the study. Fourteen were malignant. All patients underwent hormonal evaluation, functional and anatomical imaging, Weiss scoring and Ki 67 evaluation.

RESULTS

malignant tumors exhibit higher SUVmax than benign tumors (median 7.75 vs 3.06 respectively, p < 0.001) and Tmx:Lmx was 2.7 vs 1.17 for benign tumors, p < 0.001. Tmx:Lmx was positively correlated to Weiss score (p < 0.001). No significant difference was observed for Tmx:Lmx between SA and NSA overall (p = 0.851), regardless of the subgroup of tumors analyzed. Tmx:Lmx was not correlated to tumor size (p < 0.508) or 24 h free urinary cortisol level (p < 0.522).

CONCLUSIONS

no correlation was observed between Tmx:Lmx and hormonal status, however the correlation between ratio, malignancy and Weiss score confirm the utility of ¹⁸F-FDG PET/CT for the differentiation of benign from malignant adrenal lesions, irrespective of the hormone secretory status of the tumor. ¹⁸F-FDG PET/CT is a useful biomarker in the diagnosis of adrenal tumors, regardless of the secretion status.

The computed tomography adrenal wash-out analysis properly classifies cortisol secreting adrenocortical adenomas

PURPOSE

Adrenocortical lesions are characterized through imaging, hormonal and histopathological analysis. Our aim was to compare the radiological features of adrenocortical lesions with their cortisol-secreting status and histopathological Weiss score.

METHODS

Seventy five patients operated between 2004 and 2016 in the University Hospital of Nancy for either adrenocortical carcinomas (ACC) or adrenocortical adenomas (ACA) were enrolled in this study. We collected cortisol parameters, Computed Tomography (CT) scans (unenhanced density, wash-out (WO) analysis) and ¹⁸F-Fluorodeoxyglucose positron emission tomography/computed tomography (¹⁸F-FDG PET/CT) datas. The histopathological Weiss score ultimately differentiates ACA (score ≤ 2) from ACC (score ≥ 3). One-way ANOVA, Fisher's exact and unpaired t tests were used for statistical analysis with significancy reached at p < 0.05.

RESULTS

There were 23 ACC and 52 ACA with 40 patients (53%) who had an autonomous secretion of cortisol. On CT scan, ACC were larger compared to ACA (108 vs. 37 mm, p < 0.0001). A roughly similar proportion of cortisol-secreting (22/25) and non-secreting (15/19) ACA were atypical (i.e., unenhanced density value ≥ 10 Hounsfield Units [HU]), however 85% of cortisol-secreting vs. 40% of non-secreting ACA were classified as benigns by the relative WO analysis (p = 0.08). Likewise, there was a trend for a higher ¹⁸F-FDG uptake in cortisol-secreting ACA compared to non-secreting ACA (p = 0.053).

CONCLUSIONS

The relative adrenal WO analysis consolidates the benign nature of an ACA, especially in case of cortisol oversecretion, a condition known to compromise the diagnostic accuracy of the 10 HU unenhanced CT attenuation threshold.

Increased F-FDG Uptake in Bilateral Gynecomastia Secondary to Feminizing Adrenal Tumor: A Rare Case Report and Review of Literature

A 21 year old male who presented with painful enlargement of both the breasts and a hyperestrogenic state, was found to harbor a heterogeneous mass arising from the right adrenal on contrast enhanced Computed Tomography abdomen. The mass was hypermetabolic with no regional, nodal or distant metastases on Fluorine-18 Fluorodeoxyglucose Positron Emission Tomography /Computed Tomography examination. Notably, substantial tracer uptake was seen in bilateral gynecomastia. The patient underwent a right adrenalectomy with the histopathology report confirming adrenocortical carcinoma. This case demonstrates utility of FDG PET/CT in adrenocortical carcinoma. However, when interpreting FDG PET/CT as a staging tool in oncological male patients, one should consider gynecomastia as a possible cause for increased FDG uptake in the breast as it may lead to a false positive interpretation.

Contemporary imaging of incidentally discovered adrenal masses

Adrenal lesions are routinely encountered incidentally in clinical practice. Although most of these lesions are benign, malignancy needs to be excluded. Therefore, the initial clinical workup is to exclude aggressive characteristics suggesting malignancy and to identify characteristics predictive of the most common benign lesion, an adrenal adenoma. Predicting a benign adenoma using a variety of imaging modalities has been widely studied using unenhanced computed tomography (CT), contrast enhanced CT, and magnetic resonance (MR) imaging. This review article describes the currently used imaging protocols and clinical interpretation criteria of common adrenal lesions. An adenoma can be predicted if a homogenous soft tissue adrenal mass demonstrates low attenuation (upper threshold value of 10 Hounsfield Units) on unenhanced CT, demonstrates an absolute enhancement washout of ≥ 60% and/or relative enhancement washout of ≥ 40% on adrenal washout contrast enhanced CT, or demonstrates signal loss in opposed-phased MR imaging. If an adrenal adenoma cannot be predicted based upon these criteria, the lesion should be evaluated for other imaging characteristics that suggest a specific pathology, such as an adrenal cyst or myelolipoma. Although nonspecific and with limitations, 18F-fluorodeoxyglucose (FDG) PET/CT has a potential role for differentiating benign from malignant lesions based upon the amount of radiopharmaceutical uptake with malignant lesions generally having greater uptake. If clinical and/or hormonal screening suggests a pheochromocytoma, consideration can be given to 18F-dihydroxyphenylalanine (DOPA) or 123I-metaiodobenzylguanidine (MIBG) in addition to CT and MR. Finally, this review proposes a diagnostic work-up strategy for routine use in clinical practice.

Benign hormone-secreting adenoma within a larger adrenocortical mass showing intensely increased activity on 18F-FDG PET/CT

Adrenal adenomas usually show ¹⁸F-FDG activity less than that of the liver parenchyma. However, lipid-poor and hormone-secreting adenomas have been reported to show mild ¹⁸F-FDG avidity. We report on a 51-year-old female with clinical symptoms of hypercortisolemia and a large right adrenal mass detected on CT. Post-contrast CT images showed an enhancing focus in the lower pole of the mass, with corresponding markedly increased activity on ¹⁸F-FDG PET/CT. Right adrenalectomy was performed and histology revealed a benign adenoma, indicating that functioning benign adenomas can show intensely increased metabolic activity on ¹⁸F-FDG mimicking malignancy.