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

[18F]FDG-PET/CT in adrenal lesions: diagnostic performance in different clinical settings

PURPOSE

Data regarding [18F]FDG-PET/CT for the characterization of adrenal lesions are limited. Most of the studies proposed the tumor-to-liver maximum standardized uptake values (SUVratio) > 1.5 as the best cut off to predict malignancy. The aim of the study was to calculate the optimum cut off in a heterogeneous population with adrenal lesions and evaluate the diagnostic performance SUVratio >1.5.

PATIENTS AND METHODS

Retrospective analysis of adrenal lesions undergoing [18F]FDG-PET/CT (2013-2022) for different reasons (atypical adrenal incidentalomas, extra adrenal tumor staging). The diagnosis of benignity was assessed by: (i) histology; (ii) stability or minimal diameter increase (<20%/<5 mm) on 12-months follow-up for non-operated patients. The optimal SUVratio and performance of SUVratio >1.5 were calculated by ROC curves.

RESULTS

Forty-two consecutive lesions (diameter 36.1 ± 20.3 mm, 6 bilateral) underwent [18F]FDG-PET/CT (19F, age 61.2 ± 11.7 years). Twenty-nine lesions were benign, 11 malignant [8 metastases (2 bilateral) and 1 adrenocortical carcinoma (ACC)] and 2 pheochromocytomas. The SUVratio cut-off in our population was 1.55 (Sn 100%, Sp 73.7%, AUC 0.868), with similar values excluding pheochromocytomas and metastases (SUVratio cut-off 1.49, Sn 100%, Sp 96.3%, AUC 0.988). The SUVratio cut-off of 1.5 showed 100% Sn, 87% Sp, 73% PPV, and 100% NPV.

CONCLUSION

[18F]FDG-PET/CT could help in decision making process avoiding unnecessary surgery. The SUVratio cut-off of 1.5 has a good performance in a heterogenous population.

Adrenal Mass Biopsy in Patients Without Extraadrenal Primary Malignancy: A Multicenter Study

BACKGROUND. Adrenal washout CT is not useful for evaluating incidental adrenal masses in patients without known or suspected primary extraadrenal malignancy. OBJECTIVE. The purpose of our study was to evaluate the diagnostic utility of adrenal mass biopsy in patients without known or suspected extraadrenal primary malignancy. METHODS. This retrospective six-center study included 69 patients (mean age, 56 years; 32 men, 37 women) without known or suspected extraadrenal primary malignancy who underwent image-guided core needle biopsy between January 2004 and June 2021 of a mass suspected to be arising from the adrenal gland. Biopsy results were classified as diagnostic or nondiagnostic. For masses resected after biopsy, histopathologic concordance was assessed between diagnoses from biopsy and resection. Masses were classified as benign or malignant by resection or imaging follow-up, and all nondi-agnostic biopsies were classified as false results. RESULTS. The median mass size was 7.4 cm (range, 1.9-19.2 cm). Adrenal mass biopsy had a diagnostic yield of 64% (44/69; 95% CI, 51-75%). After biopsy, 25 masses were resected, and 44 had imaging follow-up. Of the masses that were resected after diagnostic biopsy, diagnosis was concordant between biopsy and resection in 100% (12/12). Of the 13 masses that were resected after nondiagnostic biopsy, the diagnosis from re-section was benign in eight masses and malignant in five masses. The 44 masses with imaging follow-up included one mass with diagnostic biopsy yielding benign adenoma and two masses with nondiagnostic biopsy results that were classified as malignant by imaging follow-up. Biopsy had overall sensitivity and specificity for malignancy of 73% (22/30) and 54% (21/39), respectively; diagnostic biopsies had sensitivity and specificity for malignancy of 96% (22/23) and 100% (21/21), respectively. Among nine nondi-agnostic biopsies reported as adrenocortical neoplasm, six were classified as malignant by the reference standard (resection showing adrenocortical carcinoma in four, resection showing adrenocortical neoplasm of uncertain malignant potential in one, imaging follow-up consistent with malignancy in one). CONCLUSION. Adrenal mass biopsy had low diagnostic yield, with low sensitivity and low specificity for malignancy. A biopsy result of adrenocortical neoplasm did not reliably differentiate benign and malignant adrenal masses. CLINICAL IMPACT. Biopsy appears to have limited utility for the evaluation of incidental adrenal masses in patients without primary extraadrenal malignancy.

Histiocytosis Presenting as Bilateral Adrenal Masses: A Case Report

Introduction

Adrenal masses are a rare diagnosis in children, with bilateral masses even less common. At present, appearance of the mass on imaging and histology can give important clues to the diagnosis; however, there is significant overlap in 10-30% of cases and it can be difficult to distinguish benign from malignant adrenal masses. As a result, the clinical presentation remains a large part of the diagnostic process, as well as thorough endocrinology evaluation to determine if the tumor is functional versus nonfunctional.

Case Presentation

We present a recent case of bilateral adrenal masses in a pediatric patient at our institution, with an unusual diagnosis of histiocytosis.

Conclusion

In this case, the diagnosis was unclear, until genetic testing and pathology allowed for expedient diagnosis and targeted therapy for this patient. We hope that presenting this case will increase physician awareness of this condition and expedite diagnosis and treatment in other patients with this rare presentation.

Alterations in 18F-FDG Uptake Patterns may Limit Cross-sectional Evaluation of Adrenal Adenomas Using Single 18F-FDG PET/CT Imaging

Adrenal adenomas are observed in up to 7% of the population and are predominantly non-functional, increased 18F-fluorodeoxyglucose (FDG) uptake is seen in only a small portion of them on 18F-FDG positron emission tomography/computed tomography (PET/CT) imaging. In this report, we present the sequential 18F-FDG PET/CT imaging findings of 2 patients with radiologically or pathologically confirmed adrenal adenomas who had severely altered 18F-FDG uptake patterns in adrenal lesions in different imaging studies of the same patient. In light of these findings, we wanted to highlight that evaluating adrenal adenomas as cross-sectional with semi-quantitative PET/CT parameters obtained from single imaging may cause misinterpretation.

The Diagnostic Value of 18F-FDG PET/CT Scan in Characterizing Adrenal Tumors

CONTEXT

Imaging plays an important role in the characterization of adrenal tumors, but findings might be inconclusive. The clinical question is whether 18F fluodeoxyglucose (18F-FDG) positron emission tomography/computed tomography (PET/CT) is of diagnostic value in this setting.

OBJECTIVE

This meta-analysis was aimed at the diagnostic value of 18F-FDG PET/CT in differentiating benign from malignant adrenal tumors discovered either as adrenal incidentaloma or during staging or follow-up of oncologic patients.

DATA SOURCES

PubMed, EMBASE, Web of Science, and Cochrane Library were searched to select articles between 2000 and 2021.

STUDY SELECTION

We included studies describing the diagnostic value of 18F-FDG PET/CT in adult patients with an adrenal tumor. Exclusion criteria were 10 or fewer participants, insufficient data on histopathology, clinical follow-up, or PET results. After screening of title and abstract by 2 independent reviewers, 79 studies were retrieved, of which 17 studies met the selection criteria.

DATA EXTRACTION

Data extraction using a protocol and quality assessment according to QUADAS-2 was performed independently by at least 2 authors.

DATA SYNTHESIS

A bivariate random-effects model was applied using R (version 3.6.2.). Pooled sensitivity and specificity of 18F-FDG PET/CT for identifying malignant adrenal tumors was 87.3% (95% CI, 82.5%-90.9%) and 84.7% (95% CI, 79.3%-88.9%), respectively. The pooled diagnostic odds ratio was 9.20 (95% CI, 5.27-16.08; P < .01). Major sources of heterogeneity (I2, 57.1% [95% CI, 27.5%-74.6%]) were in population characteristics, reference standard, and interpretation criteria of imaging results.

CONCLUSIONS

18F-FDG PET/CT had good diagnostic accuracy for characterization of adrenal tumors. The literature, however, is limited, in particular regarding adrenal incidentalomas. Large prospective studies in well-defined patient populations with application of validated cutoff values are needed.

Prediction of 2-[18F]FDG PET-CT SUVmax for Adrenal Mass Characterization: A CT Radiomics Feasibility Study

BACKGROUND

Indeterminate adrenal masses (AM) pose a diagnostic challenge, and 2-[¹⁸F]FDG PET-CT serves as a problem-solving tool. Aim of this study was to investigate whether CT radiomics features could be used to predict the 2-[¹⁸F]FDG SUVmax of AM.

METHODS

Patients with AM on 2-[¹⁸F]FDG PET-CT scan were grouped based on iodine contrast injection as CT contrast-enhanced (CE) or CT unenhanced (NCE). Two-dimensional segmentations of AM were manually obtained by multiple operators on CT images. Image resampling and discretization (bin number = 16) were performed. 919 features were calculated using PyRadiomics. After scaling, unstable, redundant, and low variance features were discarded. Using linear regression and the Uniform Manifold Approximation and Projection technique, a CT radiomics synthetic value (RadSV) was obtained. The correlation between CT RadSV and 2-[¹⁸F]FDG SUVmax was assessed with Pearson test.

RESULTS

A total of 725 patients underwent PET-CT from April 2020 to April 2021. In 150 (21%) patients, a total of 179 AM (29 bilateral) were detected. Group CE consisted of 84 patients with 108 AM (size = 18.1 ± 4.9 mm) and Group NCE of 66 patients with 71 AM (size = 18.5 ± 3.8 mm). In both groups, 39 features were selected. No statisticallyf significant correlation between CT RadSV and 2-[¹⁸F]FDG SUVmax was found (Group CE, r = 0.18 and p = 0.058; Group NCE, r = 0.13 and p = 0.27).

CONCLUSIONS

It might not be feasible to predict 2-[¹⁸F]FDG SUVmax of AM using CT RadSV. Its role as a problem-solving tool for indeterminate AM remains fundamental.

Review of Diagnostic Modalities for Adrenal Incidentaloma

Adrenal incidentalomas are common findings in clinical practice, with a prevalence of up to 4.2% in radiological studies. Due to the large number of focal lesions in the adrenal glands, it can be challenging to make a definitive diagnosis and determine the appropriate management. The purpose of this review is to present current diagnostic modalities used to preoperatively distinguish between adrenocortical adenoma (ACA) and adrenocortical cancer (ACC). Proper management and diagnosis are crucial in avoiding unnecessary adrenalectomies, which occur in over 40% of cases. A literature analysis was conducted to compare ACA and ACC using imaging studies, hormonal evaluation, pathological workup, and liquid biopsy. Before deciding on surgical treatment, the nature of the tumor can be accurately determined using noncontrast CT imaging combined with tumor size and metabolomics. This approach helps to narrow down the group of patients with adrenal tumors who require surgical treatment due to the suspected malignant nature of the lesion.

Positive Correlation Between 18 F-FDG Uptake and Tumor-Proliferating Antigen Ki-67 Expression in Adrenocortical Carcinomas

PURPOSE OF THE REPORT

Adrenocortical carcinoma (ACC) is an extremely rare endocrine malignancy, which cannot always be diagnosed during conventional radiology and hormonal investigations. 18 F-FDG PET could help predict malignancy, but more data are necessary to support future guidelines.

METHODS

A cohort of 63 patients with histologically proven ACC (n = 55) or metastatic ACC with steroid oversecretion (n = 8) was assembled. All patients underwent an 18 F-FDG PET, and the SUV max and the adrenal-to-liver SUV max ratio were calculated. The 18 F-FDG PET parameters were compared with clinical, pathological, and outcome data.

RESULTS

Fifty-six of 63 patients (89%) had an ACC with an adrenal-to-liver SUV max ratio >1.45, which was a previously defined cutoff value to predict malignancy with 100% sensitivity. Seven ACCs (11%) had a lower uptake (adrenal-to-liver SUV max <1.45), most of them with a proliferation marker Ki-67 expression level <10%. A positive correlation between 18 F-FDG PET parameters (SUV max and adrenal-to-liver SUV max ratio) and tumor size, ENSAT (European Network for the Study of Adrenal Tumors) staging, total Weiss score, and the Ki-67 was found. The strong correlation between SUV max and Ki-67 ( r = 0.47, P = 0.0009) suggests a relationship between 18 F-FDG uptake levels and tumor proliferation. No statistically significant associations between outcome parameters (progression-free or overall survival) and 18 F-FDG PET parameters were found.

CONCLUSIONS

This large cohort study shows that most cases of ACC demonstrate high 18 F-FDG uptake. However, the positive correlation observed between SUV max and Ki-67 expression levels seems to explain the possibility of identifying some ACC with a low or inexistent 18 F-FDG uptake. These findings have practical implications for the management of patients with an adrenal mass.

Simplified urinary steroid profiling by LC-MS as diagnostic tool for malignancy in adrenocortical tumors

OBJECTIVES

Preoperative identification of malignant adrenal tumors is challenging. 24-h urinary steroid profiling by LC-MS/MS and machine learning has demonstrated high diagnostic power, but the unavailability of bioinformatic models for public use has limited its routine application. We here aimed to increase usability with a novel classification model for the differentiation of adrenocortical adenoma(ACA) and adrenocortical carcinoma(ACC).

METHODS

Eleven steroids (5-pregnenetriol, dehydroepiandrosterone, cortisone, cortisol, α-cortolone, tetrahydro-11-deoxycortisol, etiocholanolone, pregnenolone, pregnanetriol, pregnanediol, and 5-pregnenediol) were quantified by LC-MS/MS in 24-h urine samples from 352 patients with adrenal tumor (281 ACA,71 ACC). Random forest modelling and decision tree algorithms were applied in training (n=188) and test sets (n=80) and independently validated in 84 patients with paired 24-h and spot urine.

RESULTS

After examining different models, a decision tree using excretions of only 5-pregnenetriol and tetrahydro-11-deoxycortisol classified three groups with low, intermediate, and high risk for malignancy. 148/217 ACA were classified as being at low, 67 intermediate, and 2 high risk of malignancy. Conversely, none of the ACC demonstrated a low-risk profile leading to a negative predictive value of 100% for malignancy. In the independent validation cohort, the negative predictive value was again 100% in both 24-h urine and spot urine with a positive predictive value of 87.5% and 86.7%, respectively.

CONCLUSIONS

This simplified LC-MS/MS-based classification model using 24-h-urine provided excellent results for exclusion of ACC and can help to avoid unnecessary surgeries. Analysis of spot urine led to similarly satisfactory results suggesting that cumbersome 24-h urine collection might be dispensable after future validation.

[Diagnostic workup of adrenal masses]

With the increasing use of abdominal imaging, adrenal masses are more frequently detected. Depending on the clinical context, the detection of an adrenal mass has different consequences for downstream testing and therapy. As adrenal masses comprise various benign and malignant aetiologies, all lesions >1 cm need further diagnostic workup. Evaluation should address radiological features with respect to potential malignancy and endocrine activity of the lesion. The majority of adrenal masses are benign, functionally inactive adenomas that need no further therapy or follow-up. Nonetheless, functional adenomas, pheochromocytomas, metastases, adrenal cancer or others account for a relevant proportion of lesions. To determine an appropriate therapy, suspicious, malignant or hormonally active tumours should be discussed in an interdisciplinary tumour board. In case of surgery of a lesion with concomitant hormonal excess, perioperative management needs to be guided by the specific requirements of this entity to avoid increased morbidity and mortality.

Clinical Spectrum of Adrenal Cushing's Syndrome and the Caution for Interpretation of Adrenocorticotrophic Hormone: A Single-Center Experience

To describe the differences in presentation, biochemistry, and radiological evaluation of various etiologies of adrenal Cushing's syndrome (CS) from a single center. To emphasize caution for interpretation of plasma adrenocorticotropic hormone (ACTH), as a spuriously unsuppressed ACTH level by immunometric assay may lead to therapeutic misadventures in adrenal CS.

DESIGN

 Retrospective, single-center, observational study.

METHODS

  Fifty-eight adrenal CS patients [Adrenocortical carcinoma (ACC), n=30; Adenoma (ACA), n=15; Primary pigmented nodular adrenocortical disease (PPNAD), n=10; ACTH independent macronodular adrenal hyperplasia (AIMAH), n=3) evaluated at a tertiary care center in western India between January 2006 to March 2020 were included. Data on demography, clinical evaluation, biochemistry, imaging, management, histopathology, and outcome were recorded in a standard format and analyzed.

RESULTS

  Cortisol secreting ACC presented at 38(1-50) years with abdominal mass in 26/30 (86.7%) and 16/30 (53.3%) had metastases at presentation. ACA with autonomous cortisol excess presented at 25(4.9-40) years with discriminating features of CS in 14/15 (93.3%), sex steroid production in 2/15, unenhanced HU <10 in only one, and relative washout >40% in 8/11 (72.7%). One ACA and eight ACC patients had plasma ACTH (by Siemens Immulite assay) > 20 pg/ml, despite hypercortisolemic state.

CONCLUSIONS

  Cortisol-secreting ACC and ACA most often present with mass effects and florid CS, respectively. Baseline HU has low sensitivity to differentiate cortisol-secreting ACA from ACC. Plasma ACTH measured by Seimens Immulite is often unsuppressed, especially in ACC patients, which can be addressed by measuring ACTH by more accurate assays.

Adrenal wash-out CT: moderate diagnostic value in distinguishing benign from malignant adrenal masses

OBJECTIVE

Reliable results of wash-out CT in the diagnostic workup of adrenal incidentalomas are scarce. Thus, we evaluated the diagnostic accuracy of delayed wash-out CT and determined thresholds to accurately differentiate adrenal masses.

DESIGN

Retrospective, single-center cohort study including 216 patients with 252 adrenal lesions who underwent delayed wash-out CT. Definitive diagnoses based on histopathology (n = 92) or comprehensive follow-up.

METHODS

Size, average attenuation values of the adrenal lesions in all CT scan phases, and absolute and relative percentage wash-out (APW/RPW) were determined by an expert radiologist blinded for clinical data. Adrenal lesions with unenhanced attenuation values >10 Hounsfield units (HU) built a subgroup (n = 142). Diagnostic accuracy was calculated.

RESULTS

The study group consisted of 171 adenomas, 32 other benign tumors, 11 pheochromocytomas, 9 adrenocortical carcinomas, and 29 other malignant tumors. All (potentially) malignant and 46% of benign lesions showed unenhanced attenuation values >10 HU. In this most relevant subgroup, the established thresholds of 60% for APW and 40% for RPW misclassified 35.9 and 35.2% of the masses, respectively. When we applied optimized cutoffs (APW >83%; RPW >58%) and excluded pheochromocytomas, we missed only one malignant tumor by APW and none by RPW. However, only 11 and 15% of the benign tumors were correctly identified.

CONCLUSIONS

Wash-out CT with the established thresholds for APW and RPW is insufficient to reliably diagnose adrenal masses. Using the proposed cutoff of 58% for RPW, malignant tumors will be correctly identified, but the added value is limited, namely 15% of patients with benign tumors can be prevented from additional imaging or even unnecessary surgery.

Primary adrenal tuberculosis infection in patients with Behcet's disease presenting as isolated adrenal metastasis by 18F-FDG PET/CT: a rare case report and literature review

Primary adrenal tuberculosis (TB) is a rare type of extrapulmonary tuberculosis (EPTB). A pathological biopsy is usually required to make a definite diagnosis due to nonspecific symptoms. Antituberculous chemotherapy is the main treatment regimen, and cortisol replacement therapy should be added when adrenal insufficiency is involved. Here, we present a 59-year-old man who had recurrence of oral and genital aphthosis for 3 years and was diagnosed with Behcet's disease (BD), which was cured by thalidomide. After 10 days of admission, the patient had sudden abdominal pain in the right upper quadrant with high fever and was diagnosed with acute cholecystitis attack, which was treated by percutaneous transhepatic gallbladder drainage (PTGBD). Further contrast-enhanced CT showed a right adrenal mass with a diameter of 2.0 cm, and PET-CT indicated intense ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) uptake in the right adrenal mass with a maximum standardized uptake value (SUV_max) of 15.2. As a metastatic adrenal mass was suspected, the patient underwent retroperitoneal laparoscopic adrenalectomy. Histopathological and immunohistochemical analysis revealed primary adrenal TB. After routine anti-tuberculosis treatment with isoniazid, rifampin, pyrazinamide and ethambutol for six months, the patient was cured and discharged. In summary, primary unilateral adrenal TB without adrenal insufficiency is difficult to diagnose only on the basis of clinical manifestations and examinations. Further studies are needed to develop an easier and more accurate diagnostic examination.

Approach to the Patient With Adrenal Incidentaloma

Adrenal tumors are commonly discovered incidentally on cross-sectional abdominal imaging performed for reasons other than adrenal mass. Incidence of adrenal tumors increased 10-fold in the past 2 decades, with most diagnosed in older adults. In any patient with a newly discovered adrenal mass, determining whether the adrenal mass is malignant and whether it is hormonally active is equally important to guide the best management. Malignancy is diagnosed in 5% to 8% of patients with adrenal tumors, with a higher risk in young patients, if history of extra-adrenal malignancy, in those with large adrenal tumors with indeterminate imaging characteristics, and in bilateral adrenal tumors. Although overt hormone excess is uncommon in adrenal incidentalomas, mild autonomous cortisol secretion can be diagnosed in up to 30% to 50% of patients. Because autonomous cortisol secretion is associated with increased cardiovascular morbidity and metabolic abnormalities, all patients with adrenal incidentalomas require work up with dexamethasone suppression test. Management of adrenal tumors varies based on etiology, associated comorbidities, and patient's preference. This article reviews the current evidence on the diagnosis and evaluation of patients with adrenal mass and focuses on management of the most common etiologies of adrenal incidentalomas.

How to Differentiate Benign from Malignant Adrenocortical Tumors?

Simple Summary

Adrenocortical carcinoma is a rare cancer with a poor prognosis. Adrenal tumors are, however, commonly identified in clinical practice. Discrimination between benign and malignant adrenal tumors is of great importance to determine the appropriate treatment and follow-up strategy. This review summarizes the current diagnostic strategies and challenges to distinguish benign from malignant adrenal lesions. We will focus both on radiological and biochemical assessments, enabling diagnosis of the adrenal lesion preoperatively, and on histopathological and a wide variety of molecular assessments that can be done after surgical removal of the adrenal lesion. Furthermore, new non-invasive strategies such as liquid biopsies, in which blood samples are used to study circulating tumor cells, tumor DNA and microRNA, will be addressed in this review.

Abstract

Adrenocortical carcinoma (ACC) is a rare cancer with a poor prognosis. Adrenal incidentalomas are, however, commonly identified in clinical practice. Discrimination between benign and malignant adrenal tumors is of great importance considering the large differences in clinical behavior requiring different strategies. Diagnosis of ACC starts with a thorough physical examination, biochemical evaluation, and imaging. Computed tomography is the first-level imaging modality in adrenal tumors, with tumor size and Hounsfield units being important features for determining malignancy. New developments include the use of urine metabolomics, also enabling discrimination of ACC from adenomas preoperatively. Postoperatively, the Weiss score is used for diagnosis of ACC, consisting of nine histopathological criteria. Due to known limitations as interobserver variability and lack of accuracy in borderline cases, much effort has been put into new tools to diagnose ACC. Novel developments vary from immunohistochemical markers and pathological scores, to markers at the level of DNA, methylome, chromosome, or microRNA. Molecular studies have provided insights into the most promising and most frequent alterations in ACC. The use of liquid biopsies for diagnosis of ACC is studied, although in a small number of patients, requiring further investigation. In this review, current diagnostic modalities and challenges in ACC will be addressed.