18 F-FDG PET/CT of Adrenal Lesions

Overview of F18-FDG uptake patterns in retroperitoneal pathologies: imaging findings, pitfalls, and artifacts

INTRODUCTION

Retroperitoneum can be the origin of a wide variety of pathologic conditions and potential space for disease spread to other compartments of the abdomen and pelvis. Computed tomography (CT) and magnetic resonance imaging (MRI) are often the initial imaging modalities to evaluate the retroperitoneal pathologies, however given the intrinsic limitations, F18-FDG PET/CT provides additional valuable metabolic information which can change the patient management and clinical outcomes. We highlight the features of retroperitoneal pathologies on F18-FDG PET/CT and the commonly encountered imaging artifacts and pitfalls. The aim of this review is to characterize primary and secondary retroperitoneal pathologies based on their metabolic features, and correlate PET findings with anatomic imaging.

CONCLUSION

Retroperitoneal pathologies can be complex, ranging from oncologic to a spectrum of non-oncologic disorders. While crosse-sectional imaging (CT and MRI) are often the initial imaging modalities to localize and characterize pathologies, metabolic information provided by F18-FDG PET/CT can change the management and clinical outcome in many cases.

Bilateral primary adrenal diffuse large B cell lymphoma: A rare presentation

Primary lymphoma of the adrenal gland is an uncommon origin of adrenal tumors; it must be explicitly invoked anytime bilateral adrenal affections are revealed. We report a case of bilateral primary adrenal diffuse large B cell lymphoma and perform a review of the literature. Our patient was a 55-year-old man who presented night sweats and a feeling of cardiac palpitations all evolving in a context of deterioration of his general condition. An ultrasound study was requested reporting a bilateral mass corresponding to the adrenal region. A thoraco-abdominopelvic CT scan was requested and revealed bilateral homogenous, polylobed, adrenal masses, discreetly enhanced after injection of contrast product. These masses were associated with multiple retroperitoneal, para-aortic, and celio-mesenteric adenopathies. Anatomopathologic examination of the percutaneous CT-guided biopsy specimen of the adrenal tumor revealed the presence of diffuse large B cell lymphoma grade IIIB according to the Ann Arbor system. Primary adrenal lymphoma PAL on its own is an extremely rare disease entity and less than 100 cases have been reported in the last 40 years. A large proportion of PAL case reports showed that this disease usually has no excretory endocrine function and the symptoms are due to the pressure effect of the mass, whereas adrenal insufficiency usually exists. Our patient presented symptoms of indrenal insufficiency which seems to be the reason for the early diagnosis. Primary bilateral adrenal lymphoma is very rare entity that should be kept in mind whenever bilateral adrenal masses are assessed in the CT scan images.

Radiomics in the characterization of lipid-poor adrenal adenomas at unenhanced CT: time to look beyond usual density metrics

OBJECTIVES

In this study, we developed a radiomic signature for the classification of benign lipid-poor adenomas, which may potentially help clinicians limit the number of unnecessary investigations in clinical practice. Indeterminate adrenal lesions of benign and malignant nature may exhibit different values of key radiomics features.

METHODS

Patients who had available histopathology reports and a non-contrast-enhanced CT scan were included in the study. Radiomics feature extraction was done after the adrenal lesions were contoured. The primary feature selection and prediction performance scores were calculated using the least absolute shrinkage and selection operator (LASSO). To eliminate redundancy, the best-performing features were further examined using the Pearson correlation coefficient, and new predictive models were created.

RESULTS

This investigation covered 50 lesions in 48 patients. After LASSO-based radiomics feature selection, the test dataset's 30 iterations of logistic regression models produced an average performance of 0.72. The model with the best performance, made up of 13 radiomics features, had an AUC of 0.99 in the training phase and 1.00 in the test phase. The number of features was lowered to 5 after performing Pearson's correlation to prevent overfitting. The final radiomic signature trained a number of machine learning classifiers, with an average AUC of 0.93.

CONCLUSIONS

Including more radiomics features in the identification of adenomas may improve the accuracy of NECT and reduce the need for additional imaging procedures and clinical workup, according to this and other recent radiomics studies that have clear points of contact with current clinical practice.

CLINICAL RELEVANCE STATEMENT

The study developed a radiomic signature using unenhanced CT scans for classifying lipid-poor adenomas, potentially reducing unnecessary investigations that scored a final accuracy of 93%.

KEY POINTS

• Radiomics has potential for differentiating lipid-poor adenomas and avoiding unnecessary further investigations. • Quadratic mean, strength, maximum 3D diameter, volume density, and area density are promising predictors for adenomas. • Radiomics models reach high performance with average AUC of 0.95 in the training phase and 0.72 in the test phase.

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.

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.

Adrenal Neoplasms: Lessons from Adrenal Multidisciplinary Tumor Boards

The radiologic diagnosis of adrenal disease can be challenging in settings of atypical presentations, mimics of benign and malignant adrenal masses, and rare adrenal anomalies. Misdiagnosis may lead to suboptimal management and adverse outcomes. Adrenal adenoma is the most common benign adrenal tumor that arises from the cortex, whereas adrenocortical carcinoma (ACC) is a rare malignant tumor of the cortex. Adrenal cyst and myelolipoma are other benign adrenal lesions and are characterized by their fluid and fat content, respectively. Pheochromocytoma is a rare neuroendocrine tumor of the adrenal medulla. Metastases to the adrenal glands are the most common malignant adrenal tumors. While many of these masses have classic imaging appearances, considerable overlap exists between benign and malignant lesions and can pose a diagnostic challenge. Atypical adrenal adenomas include those that are lipid poor; contain macroscopic fat, hemorrhage, and/or iron; are heterogeneous and/or large; and demonstrate growth. Heterogeneous adrenal adenomas may mimic ACC, metastasis, or pheochromocytoma, particularly when they are 4 cm or larger, whereas smaller versions of ACC, metastasis, and pheochromocytoma and those with washout greater than 60% may mimic adenoma. Because of its nonenhanced CT attenuation of less than or equal to 10 HU, a lipid-rich adrenal adenoma may be mimicked by a benign adrenal cyst, or it may be mimicked by a tumor with central cystic and/or necrotic change such as ACC, pheochromocytoma, or metastasis. Rare adrenal tumors such as hemangioma, ganglioneuroma, and oncocytoma also may mimic adrenal adenoma, ACC, metastasis, and pheochromocytoma. The authors describe cases of adrenal neoplasms that they have encountered in clinical practice and presented to adrenal multidisciplinary tumor boards. Key lessons to aid in diagnosis and further guide appropriate management are provided. © RSNA, 2023 Online supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center.

Risk of malignancy in adrenal tumors in patients with a history of cancer

Purpose

Adrenal gland is a common site of metastasis and on the other hand, metastases are the most frequent malignant adrenal tumors. The aim of this study was to estimate the risk of malignancy in suspicious adrenal mass in patients with a history of cancer.

Methods

This is a single-center retrospective analysis of patients with adrenal tumors treated previously for different types of cancers. Between 2004 and 2021 a hundred and six such patients were identified. Mean age of patients was 62.6 years (30-78), and mean time from oncologic treatment was 55.8 months (0-274). The most common primary cancer was kidney (RCC): 29 (27.4%), colon/rectum (CRC): 20 (18.9%) and lung (NSCLC): 20 (18.9%).

Results

Of 106 patients, 12 had hormonally active (HA) (11,3%) and 94 (88,7%) non active (HNA) tumors In group of patients with HA tumours 4 had hypercortisolaemia and 8 had elevation of urinary metanephrines. In the first group of HA patients pathology confirmed preoperative diagnosis of adrenocortical cancer and no metastasis was found. In all patients from the second group pheochromocytomas were confirmed. Primary (PM) and secondary (SM) malignancies were found in 50 patients (47.2%). In hormone inactive group only SM - 46/94 (48.9%) were diagnosed. The odds that adrenal lesion was a metastasis were higher if primary cancer was RCC (OR 4.29) and NSCLC (OR 12.3). Metastases were also more likely with high native tumor density, and bigger size in CT. The cut-off values for tumor size and native density calculated from receiver operating characteristic (ROC) curves were 37mm and 24, respectively.

Conclusion

Risk of malignancy of adrenal mass in a patient with a history of cancer is high (47,2%), regardless of hormonal status. 47,2% risk of malignancy. In preoperative assessment type of primary cancer, adrenal tumour size and native density on CT should be taken into consideration as predictive factors of malignancy. Native density exceeding 24 HU was the strongest risk factor of adrenal malignancy (RR 3.23), followed by history of lung or renal cancer (RR 2.82) and maximum tumor diameter over 37 mm (RR 2.14).

Dual Energy-Derived Metrics for Differentiating Adrenal Adenomas From Nonadenomas on Single-Phase Contrast-Enhanced CT

BACKGROUND. Adrenal masses are often indeterminate on single-phase postcontrast CT. Dual-energy CT (DECT) with three-material decomposition algorithms may aid characterization. OBJECTIVE. The purpose of this study was to compare the diagnostic performance of metrics derived from portal venous phase DECT, including virtual noncontrast (VNC) attenuation, fat fraction, iodine density, and relative enhancement ratio, for characterizing adrenal masses. METHODS. This retrospective study included 128 patients (82 women, 46 men; mean age, 64.6 ± 12.7 [SD] years) who between January 2016 and December 2019 underwent portal venous phase abdominopelvic DECT that showed a total of 139 adrenal lesions with an available reference standard based on all imaging, clinical, and pathologic records (87 adenomas, 52 nonadenomas [48 metastases, two adrenal cortical carcinomas, one ganglioneuroma, one hematoma]). Two radiologists placed ROIs to determine the following characteristics of the masses: VNC attenuation, fat fraction, iodine density normalized to portal vein, and for masses with VNC greater than 10 HU, relative enhancement ratio (ratio of portal venous phase attenuation to VNC attenuation). Readers' mean measurements were used for ROC analyses, and clinically optimal thresholds were derived as thresholds yielding the highest sensitivity at 100% specificity. RESULTS. Adenomas and nonadenomas were significantly different (all p < .001) in VNC attenuation (mean ± SD, 18.5 ± 12.9 vs 34.1 ± 8.9 HU), fat fraction (mean ± SD, 24.3% ± 8.2% vs 14.2% ± 5.6%), normalized iodine density (mean ± SD, 0.34 ± 0.15 vs 0.17 ± 0.17), and relative enhancement ratio (mean ± SD, 186% ± 96% vs 58% ± 59%). AUCs for all metrics ranged from 0.81 through 0.91. The metric with highest sensitivity for adenoma at the clinically optimal threshold (i.e., 100% specificity) was fat fraction (threshold, ≥ 23.8%; sensitivity, 59% [95% CI, 48-69%]) followed by VNC attenuation (≤ 15.2 HU; sensitivity, 39% [95% CI, 29-50%]), relative enhancement ratio (≥ 214%; sensitivity, 37% [95% CI, 25-50%]), and normalized iodine density (≥ 0.90; sensitivity, 1% (95% CI, 0-60%]). VNC attenuation at the traditional true noncontrast attenuation threshold of 10 HU or lower had sensitivity of 28% (95% CI, 19-38%) and 100% specificity. Presence of fat fraction 23.8% or greater or relative enhancement ratio 214% or greater yielded sensitivity of 68% (95% CI, 57-77%) with 100% specificity. CONCLUSION. For adrenal lesions evaluated with single-phase DECT, fat fraction had higher sensitivity than VNC attenuation at both the clinically optimal threshold and the traditional threshold of 10 HU or lower. CLINICAL IMPACT. By helping to definitively diagnose adenomas, DECT-derived metrics can help avoid downstream imaging for incidental adrenal lesions.

Approach to the Patient With Adrenal Hemorrhage

Adrenal hemorrhage is an uncommon, underrecognized condition that can be encountered in several clinical contexts. Diagnosing adrenal hemorrhage is challenging due to its nonspecific clinical features. Therefore, it remains a diagnosis that is made serendipitously on imaging of acutely unwell patients rather than with prospective clinical suspicion. Adrenal hemorrhage can follow abdominal trauma or appear on a background of predisposing conditions such as adrenal tumors, sepsis, or coagulopathy. Adrenal hemorrhage is also increasingly reported in patients with COVID-19 infection and in the context of vaccine-induced immune thrombocytopenia and thrombosis. Unexplained abdominal pain with hemodynamic instability in a patient with a predisposing condition should alert the physician to the possibility of adrenal hemorrhage. Bilateral adrenal hemorrhage can lead to adrenal insufficiency and potentially fatal adrenal crisis without timely recognition and treatment. In this article, we highlight the clinical circumstances that are associated with higher risk of adrenal hemorrhage, encouraging clinicians to prospectively consider the diagnosis, and we share a diagnostic and management strategy.

Multimodality imaging of adrenal gland pathologies: A comprehensive pictorial review

The assessment of acute abdominal and pelvic emergencies typically involves a multimodal approach consisting of plain radiographs, ultrasound, computed tomography (CT), and rarely magnetic resonance imaging (MRI). Although MRI is not traditionally employed in acute care settings, there are several instances in which MRI provides superior functional and prognostic information. In this manuscript, we highlight multimodal findings of adrenal gland emergencies: Hemorrhage, infarction, and infection. The purpose of our study is to highlight significant findings in various modalities, including CT, MRI, ultrasound, and PET/CT. Due to the scarcity of published data and limited clinical use, primary ultrasound findings are limited in our multimodal review. In conclusion, we find that synergistic use of CT, MRI, and functional imaging provides an effective tool for evaluation and management of adrenal pathology.

PET-CT in Clinical Adult Oncology: III. Gastrointestinal Malignancies

Simple Summary

Positron emission tomography (PET), typically combined with computed tomography (CT), has become a critical advanced imaging technique in oncology. With PET-CT, a radioactive molecule (radiotracer) is injected in the bloodstream and localizes to sites of tumor because of specific cellular features of the tumor that accumulate the targeting radiotracer. The CT scan, performed at the same time, provides information to facilitate the characterization of radioactivity from deep or dense structures, and to provide detailed anatomic information. PET-CT has a variety of applications in oncology, including staging, therapeutic response assessment, restaging and surveillance. This series of six review articles provides an overview of the value, applications, and imaging interpretive strategies of PET-CT in the more common adult malignancies. The third report in this series provides a review of PET-CT imaging in gastrointestinal malignancies.

Abstract

PET-CT is an advanced imaging modality with many oncologic applications, including staging, assessment of response to therapy, restaging and longitudinal surveillance for recurrence. The goal of this series of six review articles is to provide practical information to providers and imaging professionals regarding the best use of PET-CT for specific oncologic indications, and the potential pitfalls and nuances that characterize these applications. In the third of these review articles, key tumor-specific clinical information and representative PET-CT images are provided to outline the role that PET-CT plays in the management of patients with gastrointestinal malignancies. The focus is on the use of ¹⁸F fluorodeoxyglucose (FDG), rather than on research radiopharmaceuticals under development. Many different types of gastrointestinal tumors exist, both pediatric and adult. A discussion of the role of FDG PET-CT for all of these is beyond the scope of this review. Rather, this article focuses on the most common adult gastrointestinal malignancies that may be encountered in clinical practice. The information provided here will provide information outlining the appropriate role of PET-CT in the clinical management of patients with gastrointestinal malignancies for healthcare professionals caring for adult cancer patients. It also addresses the nuances and provides interpretive guidance related to PET-CT for imaging providers, including radiologists, nuclear medicine physicians and their trainees.

Parotid gland incidentalomas: A single-institution experience

PURPOSE

Parotid gland incidentaloma (PGI) management has not been well characterized in the literature. This study assesses clinicopathologic features, initial evaluation, management, and outcomes of PGIs discovered on various imaging modalities.

MATERIALS AND METHODS

This is a retrospective case series from a single academic institution. The study cohort included 34 patients with parotid gland incidentalomas discovered between January 2009 and December 2019.

RESULTS

Parotid gland incidentalomas were most frequently identified on magnetic resonance imaging (16 patients, 47.1%). Most patients (26 patients, 76.5%) underwent further evaluation with subsequent imaging, most often magnetic resonance imaging (18 patients, 69.2%), and fine needle aspiration biopsy (33 patients, 97.1%). Most tumors were benign on fine needle aspiration biopsy (19 patients, 57.6%). Most cases (21 patients, 61.8%) were managed with observation without parotidectomy. Malignant findings on fine needle aspiration cytology were associated with increased likelihood of undergoing parotidectomy (25% vs 0%; p = 0.04). Among the patients who received a parotidectomy, most (8 patients, 61.5%) had benign findings on final histopathology.

CONCLUSION

Parotid gland incidentalomas were discovered across a diverse set of imaging modalities in our institution. Magnetic resonance imaging and fine needle aspiration were often performed for further evaluation. Most cases were found to be benign on fine needle aspiration and were managed with observation. These findings highlight the necessity of appropriate work-up for these tumors, and the need for shared decision making between the patient and the physician in selecting the appropriate treatment strategy.

Bilateral cytomegalovirus infection of the adrenal glands revealed by 18F-FDG PET/CT in a patient with T-cell lymphoma

This case report demonstrates the possible subclinical adrenal and pancreatic involvement in immunocompromised patients (in particular those with lymphoma) with a CMV infection and the role of whole-body 18F-FDG PET/CT in detecting these lesions.

Adrenal hemorrhage and hemorrhagic masses; diagnostic workup and imaging findings

Adrenal hemorrhage (AH) is a rare condition. It can be traumatic or non-traumatic. Most common causes are septicemia, coagulopathy or bleeding diathesis, and underlying neoplasms. Other reported less common causes of AH are COVID-19 and neonatal stress. Clinical diagnosis of AH is challenging due to its non-specific presentation and occurrence in the setting of acute medical illness. Therefore, most cases are diagnosed incidentally on imaging. Having high clinical suspicion in the proper clinical setting for AH is crucial to avoid life-threatening adrenal insufficiency that occurs in 16-50% of patients with bilateral AH. We discuss the clinical situations that predispose to AH, review the imaging features on different imaging modalities, highlight a variety of clinical cases, imaging features that should be concerning for an underlying neoplasm, and outline the potential role of interventional radiology in management of AH.

Sporadic Primary Pheochromocytoma: A Prospective Intra-Individual Comparison of Six Imaging Tests (CT, MRI, and PET/CT Using 68Ga-DOTATATE, FDG, 18F-FDOPA, and 18F-FDA)

Background: Recent professional society guidelines for radionuclide imaging of sporadic pheochromocytoma (PHEO) recommend 18F-FDOPA as the radiotracer of choice, deeming 68Ga-DOTATATE and FDG to be secondand third-line agents, respectively. An additional agent, 18F-FDA, remains experimental for PHEO detection. A paucity of research has performed head-to-head comparison among these agents. Purpose: To perform an intra-individual comparison of 68Ga-DOTATATE PET/CT, FDG PET/CT, 18F-FDOPA PET/CT, 18F-FDA PET/CT, CT, and MRI in visualization of sporadic primary PHEO. Methods: This prospective study enrolled patients referred with clinical suspicion for sporadic PHEO. Patients were scheduled for 68Ga-DOTATATE PET/CT, FDG PET/CT, 18F-FDOPA PET/CT, 18F-FDA PET/CT, whole-body staging CT (portal venous phase), and MRI, within a 3-month period. PET/CT examinations were reviewed by two nuclear medicine physicians, and CT and MRI were reviewed by two radiologists; differences were resolved by consensus. Readers scored lesions in terms of confidence in diagnosis of PHEO (1-5 scale; 4-5 considered positive for PHEO). Lesion-to-liver SUVmax was computed using both readers' measurements. Interreader agreement was assessed, using intraclass correlation coefficients (ICCs) for SUVmax. Analysis included only patients with histologically- confirmed PHEO on resection. Results: The analysis included 14 patients (8 women, 6 men; mean age, 52.4±16.8 years) with PHEO. Both 68Ga-DOTATATE PET/CT and FDG PET/CT were completed in 14/14 patients, 18F-FDOPA PET/CT in 11/14, 18F-FDA PET/CT in 7/14, CT in 12/14, and MRI in 12/14. Mean conspicuity score for PHEO was 5.0±0.0 for 18F-FDOPA PET/ CT, 4.7±0.5 for MRI, 4.6±0.8 for 18F-FDA PET/CT, 4.4±1.0 for 68Ga-DOTATATE PET/CT, 4.3±1.0 for CT, and 4.1±1.5 for FDG PET/CT. The positivity rate for PHEO was 100.0% (11/11) for 18F-FDOPA PET/CT, 100.0% (12/12) for MRI, 85.7% (6/7) for 18F-FDA PET/CT, 78.6% (11/14) for FDG PET/CT, 78.6% (11/14) for 68Ga-DOTATATE, and 66.7% (8/12) for CT. Lesion-to-liver SUVmax was 10.5 for 18F-FDOPA versus 3.0-4.2 for the other tracers. Interreader agreement across modalities ranged from 85.7-100.0% for lesion positivity and from ICC=0.55-1.00 for SUVmax measurements. Conclusion: Findings from this small intra-individual comparative study support 18F-FDOPA PET/CT as a preferred firstline imaging modality in evaluation of sporadic PHEO. Clinical Impact: This study provides data supporting current guidelines for imaging evaluation of suspected PHEO.

18F-FDG PET/CT Sheds Light on a Case of Hyponatremia

A 76-y-old man with hypoosmolar hyponatremia of unknown origin was referred to the nuclear medicine department for ¹⁸F-FDG PET/CT to exclude a malignant cause. Increased ¹⁸F-FDG uptake in both adrenal glands was observed and investigated.

Adrenocortical carcinoma: current state of the art, ongoing controversies, and future directions in diagnosis and treatment

Adrenocortical carcinoma (ACC) is a rare, aggressive malignancy with an annual incidence of ~1 case per million population. Differentiating between ACC and benign adrenocortical tumors can be challenging in patients who present with an incidentally discovered adrenal mass, due to the limited specificity of standard diagnostic imaging. Recently, urine steroid metabolite profiling has been prospectively validated as a novel diagnostic tool for the detection of malignancy with improved accuracy over current modalities. Surgery represents the only curative treatment for ACC, although local recurrence and metastases are common, even after a margin-negative resection is performed. Unlike other intra-abdominal cancers, the role of minimally invasive surgery and lymphadenectomy in ACC is controversial. Adjuvant therapy with the adrenolytic drug mitotane is used to reduce the risk of recurrence after surgery, although evidence supporting its efficacy is limited; it is also currently unclear whether all patients or a subset with the highest risk of recurrence should receive this treatment. Large-scale pan-genomic studies have yielded insights into the pathogenesis of ACC and have defined distinct molecular signatures associated with clinical outcomes that may be used to improve prognostication. For patients with advanced ACC, palliative combination chemotherapy with mitotane is the current standard of care; however, this is associated with poor response rates (RR). Knowledge from molecular profiling studies has been used to guide the development of novel targeted therapies; however, these have shown limited efficacy in early phase trials. As a result, there is an urgent unmet need for more effective therapies for patients with this devastating disease.

Adrenalitis tuberculosa: a propósito de una actualización

Introducción: la insuficiencia suprarrenal primaria (IA) descrita por Thomas Addison en 1855 atribuía como principal causa a la infección por tuberculosis (TBC) diseminada, pero con el paso del tiempo ha disminuido en los países desarrollados. En aquellos en vías de desarrollo se mantiene alta esta etiología infecciosa, en especial en pacientes con VIH. Objetivo: realizar una revisión narrativa de la literatura reciente sobre la adrenalitis TBC, incluyendo el enfoque, manejo y seguimiento en los casos de insuficiencia suprarrenal primaria (IA). Materiales y métodos:  búsqueda y análisis de los artículos disponibles en los últimos 5 años bajo los descriptores en ciencias de la salud (DeCS) enfermedad de Addison, tuberculosis, insuficiencia suprarrenal primaria y adrenalitis en español en las bases de Google scholar y LILACS, y en inglés en PubMed y ClinicalKey. Conclusiones:  la insuficiencia adrenal o adrenalitis por TBC ha descendido como causa de IA primaria, pero en el contexto de reemergencia de infección por VIH, continúa siendo una causa importante de IA en países en desarrollo. En estos casos además de la suplencia con corticosteroides el tratamiento de la causa específica es de importancia para impactar en la respuesta clínica, la supervivencia y la calidad de vida.

Benign Adrenal Nodule Mimicking Lymphoma Differentially Diagnosed by 18F-FDG and 18F-FGln PET/CT

ABSTRACT

18F-FDG and 18F-(2S,4R)4-fluoroglutamine (18F-FGln) PET/CT were performed in a 58-year-old woman with suspected small intestinal malignancy for differential diagnosis and staging. 18F-FDG and 18F-FGln PET images showed consistent intense hypermetabolic lesion activity in part of the small intestine. Moreover, 18F-FDG/PET demonstrated a focal of increased radiotracer uptake in left adrenal lesion, which did not show abnormal activity on 18F-FGln/PET. The postoperative pathology confirmed that it was a peripheral T-cell lymphomas of the intestine, and the adrenal lesion was considered benign after continuous CT follow-up for more than 2 years.

Imaging Manifestations of Genitourinary Tuberculosis

The genitourinary region is one of the most common sites of extrapulmonary tuberculosis (TB) involvement. The imaging features of genitourinary TB are protean and can mimic other entities, including malignancy, and pose a diagnostic dilemma. Hematogenous seeding and lymphatic spread of mycobacteria from pulmonary, tonsillar, and nodal TB are implicated in the pathogenesis of genitourinary TB. In addition, contiguous extension from the urinary tract and sexual transmission are described as sources of genital TB. Genitourinary TB can be indolent and results in nonspecific signs and symptoms; thus, imaging has a vital role in the working diagnosis for these cases. Classic uroradiologic signs of genitourinary TB are primarily described from the era of intravenous urography and conventional radiography. Now, CT, CT urography, MRI, and US are used in the diagnosis and management. Familiarity with the imaging features of genitourinary TB may help guide the diagnosis and, in turn, lead to timely management. US has a vital role in the evaluation of scrotal and female genital TB. MRI offers superior soft-tissue contrast resolution and excellent depiction of anatomic detail. The various imaging manifestations of genitourinary TB are highlighted. ^©RSNA, 2021.

Can we differentiate neoplastic and non-neoplastic spontaneous adrenal bleeding? Imaging findings with radiopathologic correlation

Spontaneous adrenal bleeding is a rare clinical event with non-specific clinical features. Life-threatening bleeding in the adrenal glands may be promptly diagnosed with imaging. Computed tomography (CT) is generally the first imaging modality to be used in these patients. However, in the acute phase of bleeding, it may be difficult to detect the underlying mass from the large hematoma. In these patients, additional imaging studies such as magnetic resonance imaging or positron emission tomography/CT may be utilized to rule out a neoplastic mass as the source of bleeding. In patients where an underlying neoplastic mass could not be identified at the time of initial diagnosis, follow-up imaging may be helpful after the acute phase subsides.

The value of 18F-FDG PET-CT and 131I-norcholesterol scintigraphy in the characterization of high-risk adrenal masses

PURPOSE

To assess the value of F-FDG PET-computed tomography (CT) and I-norcholesterol scintigraphy in noninvasive characterization of high-risk adrenal lesions using surgical pathology as the gold standard.

METHODS

We retrospectively reviewed clinical cases referred to the adrenal multidisciplinary team in a tertiary centre over the last 6 years. Inclusion criteria were the presence of indeterminate adrenal lesions and performance of combined imaging with 2-deoxy-2-[fluorine-18] fluoro- D-glucose Positron emission tomography/ computed tomography and I-norcholesterol scans. The accuracy of CT, PET-CT and I-norcholesterol findings was assessed by comparison with the postoperative histopathological outcome.

RESULTS

Sixteen patients fulfilled the inclusion criteria. Ten underwent unilateral adrenalectomy, and six had clinical follow-up. The number of cases categorized as concerning on the basis of unenhanced CT, F-FDG PET-CT and I-norcholesterol was 11, 9 and 2, respectively. The mean diameter of adrenal lesions was 4.5 ± 1.9 cm. Average SUVmax of the FDG-avid adrenal lesions was 5.0 ± 2.0 (range 3.5-9.7). Fourteen adrenal masses showed I-norcholesterol uptake. All adrenal masses turned out to be benign lesions.

CONCLUSION

Conventional CT and FDG PET parameters are not adequately specific for determination of a benign lesion in this selected cohort of high-risk patients. Use of I-norcholesterol in this patient cohort may provide additional value.

18F-FDG PET/CT Imaging of Adrenal Liposarcoma

Liposarcoma is a common soft tissue sarcoma in retroperitoneum, but adrenal liposarcoma is rare. We here described a 61-year-old man with left-upper-quadrant pain, hypertension, and weight loss. Abdominal CT showed a large, heterogeneously enhanced mass on the left adrenal area, which compressed the surrounding pancreas, spleen, and left kidney. Subsequent FDG PET/CT demonstrated heterogeneous uptake by the lesion. Postoperative pathological findings confirmed the diagnosis of adrenal liposarcoma.

Adrenal cortical adenoma: current update, imaging features, atypical findings, and mimics

Adrenal adenoma is the most common adrenal lesion. Due to its wide prevalence, adrenal adenomas may demonstrate various imaging features. Thus, it is important to identify typical and atypical imaging features of adrenal adenomas and to be able to differentiate atypical adrenal adenomas from potentially malignant lesions. In this article, we will discuss the diagnostic approach, typical and atypical imaging features of adrenal adenomas, as well as other lesions that mimic adrenal adenomas.

Management of incidental adrenal masses: an update

OBJECTIVE

To review the current evidence and guidelines for diagnosis and management of incidental adrenal masses with a focus on the recent changes made by the American College of Radiology (ACR) Incidental Findings Committee.

CONCLUSION

Incidentally detected adrenal nodules are a commonly encountered finding estimated to occur in 5-7% of the adult population. By following current recommendations, radiologists can improve patient care by efficiently determining which masses require further diagnostic testing and which masses can be considered benign and not require further follow-up.

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.

Bilateral primary adrenal lymphoma successfully treated with non-CHOP chemotherapy regimen

Primary bilateral non-Hodgkin's lymphoma of the adrenal gland is a rare presentation with <200 reported cases. We report a 70-year-old man who presented with vomiting and abdominal pain for 2 weeks and was subsequently diagnosed to have high-grade lymphoma of the adrenal glands. The patient was then started on a rituximab-bendamustine chemotherapy regimen. The patient tolerated treatment well without significant side effects. Repeat positron emission tomography CT scan after four cycles of chemotherapy showed complete response. The patient has completed six cycles of chemotherapy and is on regular follow-up with no signs of relapse.

Using the modified Dixon technique to evaluate incidental adrenal lesions on 3T MRI

OBJECTIVES

To use the mDIXON-Quant sequence to quantify the fat fraction of adrenal lesions discovered incidentally on CT studies. To analyze the relation between the signal loss between in-phase and out-of-phase T1-weighted sequences and the fat fraction in mDIXON-Quant. To compare the sensitivity and specificity of the two methods for characterizing adrenal lesions.

MATERIAL AND METHODS

This prospective descriptive study included 31 patients with incidentally discovered adrenal lesions evaluated with 3T MRI using in-phase and out-of-phase T1-weighted sequences and mDIXON-Quant; the fat fraction of the adrenal lesions was measured by mDIXON-Quant and by calculating the percentage of signal loss between in-phase and out-of-phase T1-weighted sequences.

RESULTS

The percentage of signal loss was significantly higher in the group of patients with adenoma (61.3% ± 20.4% vs. 5.1% ± 5.8% in the group without adenoma, p<0.005). The mean fat fraction measured by mDIXON-Quant was also higher for the adenomas (26.9% ±10.8% vs. 3.4% ± 3.0%, p<0.005).The area under the ROC curve was 0.99 (0.96 - 1.00) for the percentage of signal loss and 0.98 (0.94 - 1.00) for the fat fraction measured by mDIXON-Quant. The cutoffs obtained were 24.42% for the percentage of signal loss and 9.2% for the fat fraction measured by mDIXON-Quant. The two techniques had the same values for diagnostic accuracy: sensitivity 96% (79.6 - 99.9), specificity 100% (39.8 - 100.0), positive predictive value 100% (85.8 - 100.0), and negative predictive value 80% (28.4 - 99.5).

CONCLUSION

The fat fraction measured by the modified Dixon technique can differentiate between adenomas and other adrenal lesions with the same sensitivity and specificity as the percentage of signal loss between in-phase and out-of-phase T1-weighted sequences.

Imaging of F-18 FDG PET/CT and follow up of bilateral invasive adrenal diffuse large B cell lymphoma mimicking adrenocortical carcinoma

The incidence of malignant adrenal tumors, including primary adrenal lymphoma (PAL) and adrenocortical carcinoma (ACC), is rather low. Early differentiation between ACC and PAL is necessary because the therapeutic strategies for the two differ and the prognosis of each disease is poor. Unfortunately, there is no pathognomonic characteristic of PAL, so radiologists have difficulty in differentiating it from ACC. To our knowledge, there have been only two case reports on ACC that was evaluated and followed up using F-18 FDG PET/CT. The previously reported cases were simple, involving only the bilateral adrenal glands. Here, we report on a 52-year-old man diagnosed with PAL that radiologically mimicked ACC. He had findings of heterogeneous enhancement on CT, several adjacent lymphadenopathies with internal necrosis, and abutting hepatic and bilateral crural invasion. After pathological confirmation, we monitored his prognosis using F-18 FDG PET/CT after three cycles of rituximab-CHOP and again after six cycles of treatment.

Primary adrenal lymphoma with initial presentation concerning for bilateral adrenal pheochromocytomas

Primary adrenal non-Hodgkin's lymphoma is rarely encountered. Clinical presentation is non-specific with fatigue, abdominal pain and B-symptoms being more commonly reported. We report a case of primary bilateral adrenal lymphoma who initially presented with clinical features suspicious for pheochromocytoma. The patient was recently diagnosed with hypertension and had a family history of early ischaemic heart disease. Plasma free metanephrines were also elevated. Pheochromocytoma was deemed unlikely following multiple investigations and the diagnosis of lymphoma was made following adrenal biopsy. Partial response was noted on positron emission tomography CT scan following four cycles of chemotherapy but failed to remit after six cycles of chemotherapy. Subsequently, he received 20 fractions of radiation to his adrenal glands and is now awaiting further imaging. The presentation of primary adrenal lymphoma can be variable and given that the diagnosis is obtained through tissue sampling, pheochromocytoma should be excluded due to risk of a potentially fatal adrenergic crisis.

Fat-Containing Hypermetabolic Masses on FDG PET/CT: A Spectrum of Benign and Malignant Conditions

OBJECTIVE

This article focuses on identifying the imaging appearances of hypermetabolic fatty masses and masslike lesions on PET/CT and understanding the diagnostic challenges radiologists may face while interpreting findings of these lesions on PET/CT. This article provides an approach to aid in the diagnosis of these lesions and the appropriate management of patients.

CONCLUSION

Both malignant and benign fat-containing masses and masslike lesions can show hypermetabolic activity on PET/CT. Although the differential diagnosis is broad, clinical history, anatomic location, and knowledge of anatomic variants and imaging features can help radiologists avoid misinterpretation of benign fatty lesions as malignancy.

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.

Update on advances in molecular PET in urological oncology

Integrated positron emission tomography/computed tomography (PET/CT) with 2-[(18)F]fluoro-2-deoxy-D-glucose ((18)F-FDG) has emerged as a powerful tool for the combined metabolic and anatomic evaluation of many cancers. In urological oncology, however, the use of (18)F-FDG has been limited by a generally low tumor uptake, and physiological excretion of FDG through the urinary system. (18)F-FDG PET/CT is useful when applied to specific indications in selected patients with urological malignancy. New radiotracers and positron emission tomography/magnetic resonance imaging (PET/MRI) are expected to further improve the performance of PET in uro-oncology.

18F-FDG PET/CT in the post-operative monitoring of patients with adrenocortical carcinoma

CONTEXT

The role of (18)F-labeled 2-fluoro-2-deoxy-d-glucose (FDG) positron emission tomography (PET)/computed tomography (CT) in the post-operative monitoring of patients with adrenocortical carcinoma (ACC) is still unclear.

OBJECTIVE

To assess the accuracy of FDG PET/CT to diagnose ACC recurrence in a real world setting.

DESIGN AND METHODS

Retrospective evaluation of data of 57 patients with presumed ACC recurrence at CT scan who underwent FDG PET/CT within a median time of 20 days. We compared the results of either FDG PET/CT or CT with a gold standard confirmation of recurrence (positive histopathology report of removed/biopsied lesions or radiological progression of target lesions at follow-up) to assess their diagnostic performance at different body sites to correctly categorize target lesions. We also assessed whether FDG PET/CT findings may be useful to inform the management strategy.

RESULTS

In 48 patients with confirmed ACC recurrence, we found that FDG PET/CT had lower sensitivity than CT in diagnosing liver and lung recurrences of ACC. FDG PET/CT had higher specificity than CT in categorizing liver lesions. FDG PET/CT had a greater positive likelihood ratio than CT to identify liver and abdominal ACC recurrences. The management strategy was changed based on FDG PET/CT findings in 12 patients (21.1%).

CONCLUSIONS

The greater sensitivity of CT may be partly expected due the specific inclusion criteria of the study; however, the greater specificity of FDG PET/CT was particularly useful in ruling out suspected ACC recurrences found by CT. Thus, use of FDG PET/CT as a second-line test in the post-operative surveillance of ACC patients following CT finding of a potential recurrence may have a significant impact on patient management.

Imaging Features of Various Adrenal Neoplastic Lesions on Radiologic and Nuclear Medicine Imaging

OBJECTIVE

The purpose of this review is to describe the features of diverse adrenal neoplastic lesions on radiologic and nuclear medicine imaging.

CONCLUSION

Various neoplastic lesions with or without malignant potential can occur in the adrenal gland. Knowledge of imaging features of adrenal lesions on radiologic and nuclear medicine imaging will facilitate differential diagnosis and assessment of malignant potential.