Practical Approach to Adrenal Imaging

18F-FDG-PET/CT-based machine learning model evaluates indeterminate adrenal nodules in patients with extra-adrenal malignancies

BACKGROUND

To assess the value of an 18F-FDG-positron emission tomography/computed tomography (PET/CT)-based machine learning model for distinguishing between adrenal benign nodules (ABNs) and adrenal metastases (AMs) in patients with indeterminate adrenal nodules and extra-adrenal malignancies.

METHODS

A total of 303 patients who underwent 18F-FDG-PET/CT with indeterminate adrenal nodules and extra-adrenal malignancies from March 2015 to June 2021 were included in this retrospective study (training dataset (n = 182): AMs (n = 97), ABNs (n = 85); testing dataset (n = 121): AMs (n = 68), ABNs (n = 55)). The clinical and PET/CT imaging features of the two groups were analyzed. The predictive model and simplified scoring system for distinguishing between AMs and ABNs were built based on clinical and PET/CT risk factors using multivariable logistic regression in the training cohort. The performances of the predictive model and simplified scoring system in both the training and testing cohorts were evaluated by the areas under the receiver operating characteristic curves (AUCs) and calibration curves. The comparison of AUCs was evaluated by the DeLong test.

RESULTS

The predictive model included four risk factors: sex, the ratio of the maximum standardized uptake value (SUVmax) of adrenal lesions to the mean liver standardized uptake value, the value on unenhanced CT (CTU), and the clinical stage of extra-adrenal malignancies. The model achieved an AUC of 0.936 with a specificity, sensitivity and accuracy of 0.918, 0.835, and 0.874 in the training dataset, respectively, while it yielded an AUC of 0.931 with a specificity, sensitivity, and accuracy of 1.00, 0.735, and 0.851 in the testing dataset, respectively. The simplified scoring system had comparable diagnostic value to the predictive model in both the training (AUC 0.938, sensitivity: 0.825, specificity 0.953, accuracy 0.885; P = 0.5733) and testing (AUC 0.931, sensitivity 0.735, specificity 1.000, accuracy 0.851; P = 1.00) datasets.

CONCLUSIONS

Our study showed the potential ability of a machine learning model and a simplified scoring system based on clinical and 18F-FDG-PET/CT imaging features to predict AMs in patients with indeterminate adrenal nodules and extra-adrenal malignancies. The simplified scoring system is simple, convenient, and easy to popularize.

Oncocytic adrenocortical tumour presenting as an incidentaloma: a diagnostic challenge

Oncocytic adrenocortical neoplasms are a rare histopathological subtype of adrenal tumours which are usually benign and, if malignant, are less likely to metastasise. We report a case of a non-functioning oncocytic adrenocortical tumour, identified incidentally in a middle-aged woman. It was initially reported as a left-sided 3.5×3.4×5.6 cm adrenal adenoma. It however increased in size to 5.4×4.0×4.3 cm on follow-up scans. Subsequent review of the scans revealed an indeterminate lesion with a precontrast density of 30 Hounsfield units, an absolute washout of 42.6% and a relative washout of 28.6%. As a result, laparoscopic left adrenalectomy was performed. Histology confirmed oncocytic adrenocortical carcinoma when using the Lin-Weiss-Bisceglia system, though it was deemed benign when using the Helsinki scoring system. There has been no evidence of recurrence to date. This case highlights the potential pitfalls in the diagnosis of oncocytic neoplasms and the increased specificity of the Helsinki score in assessing metastatic potential.

Assessment of Adrenal Computed Tomography Characteristics in Cats with Nonadrenal Disease

Adrenal computed tomography characteristics (aCTc) in healthy cats are known, but reference intervals for diseased cats are lacking. aCTc of cats without evidence of adrenal disease (NAD group) were compared to parameters of cats with possible concurrent adrenal disease (PAD group). The PAD group was assessed for adrenal masses or other morphological deviations using the NAD group as reference. Associations of aCTc with patient variables were explored, and all results were compared with published aCTc of healthy cats. No incidental adrenal masses were identified in the PAD group (n = 92), and only few aCTc differed compared to the NAD group (n = 30). The NAD group showed similar associations of patient variables and aCTc as length (right: 11.5 ± 2.2 mm, left: 11.8 ± 1.7 mm), width (right: 6.4 ± 1.2 mm, left: 5.4 ± 0.8 mm), height (right: 4.5 ± 0.9 mm, left: 4.5 ± 0.8 mm), attenuation (right: 33.1 ± 5.0 Hounsfield units, left: 32.5 ± 5.3 Hounsfield units) and position, but markedly more mineralization (right: 10%, left: 13.3%) than reported in healthy cats. This study provides references of aCTc for diseased cats without evidence of adrenal disease. The result suggests that adrenal incidentalomas seem to be rare in cats.

Outcomes and toxicities in oligometastatic patients treated with stereotactic body radiotherapy for adrenal gland metastases: A multi-institutional retrospective study

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SBRT to adrenal gland oligometastases achieves a satisfactory local control and OS.

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A minimum PTV dose BED₁₀ > 46 Gy was associated with an improved OS and LRFS.

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A prescribed BED₁₀ > 70 Gy was correlated with improved local control.

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High adrenal metastases volume should not preclude the delivery of SBRT.

Background

Studies reporting SBRT outcomes in oligometastatic patients with adrenal gland metastases (AGM) are limited. Herein, we present a multi-institutional analysis of oligometastatic patients treated with SBRT for AGM.

Material/methods

The Consortium for Oligometastases Research (CORE) is among the largest retrospective series of patients with oligometastases. Among CORE patients, those treated with SBRT for AGM were included. Clinical and dosimetric data were collected. Adrenal metastatic burden (AMB) was defined as the sum of all adrenal GTV if more than one oligometastases is present.

Competing risk analysis was used to estimate actuarial cumulative local recurrence (LR) and widespread progression (WP). Kaplan-Meier method was used to report overall survival (OS), local recurrence-free survival (LRFS), and progression-free survival (PFS). Treatment related toxicities were also reported.

Results

The analysis included 47 patients with 57 adrenal lesions. Median follow-up was 18.2 months. Median LRFS, PFS, and OS were 15.3, 5.3, and 19.1 months, respectively. A minimum PTV dose BED₁₀ > 46 Gy was associated with an improved OS and LRFS. A prescribed BED₁₀ > 70 Gy was an independent predictor of a lower LR probability. AMB>10 cc was an independent predictor of a lower risk for WP. Only one patient developed an acute Grade 3 toxicity consisting of abdominal pain.

Conclusion

SBRT to AGM achieved a satisfactory local control and OS in oligometastatic patients. High minimum PTV dose and BED₁₀ prescription doses were predictive of improved LR and OS, respectively. Prospective studies are needed to determine comprehensive criteria for patients SBRT eligibility and dosimetric planning.

MRI in pregnant patients with suspected abdominal and pelvic cancer: a practical guide for radiologists

The incidence of abdominal and pelvic cancer in pregnancy is low, but it is rising as the population of pregnant women gets older. Depending on disease stage, gestational age and patient's preference, active surveillance as well as surgery and chemotherapy are feasible options during pregnancy. Correct diagnosis and staging of the tumor is crucial for choosing the best therapeutic approach. Moreover, a reproducible modality to assess the treatment response is requested. Magnetic resonance imaging (MRI) is commonly used with good results for the local staging and treatment response evaluation of most abdominal and pelvic cancers in nonpregnant patients, and it is considered relatively safe during pregnancy. The purpose of this article is to analyze the most relevant topics regarding the use of MRI in pregnant women with abdominal and pelvic cancer. We discuss MRI safety during pregnancy, including the use of gadolinium-based contrast agents (GBCAs), how to prepare the patient for the exam and MRI technique. This will be followed by a brief review on the most common malignancies diagnosed during pregnancy and their MRI appearance.

Hyperattenuating adrenal lesions in lung cancer: biphasic CT with unenhanced and 1-min enhanced images reliably predicts benign lesions

OBJECTIVES

To investigate usefulness of biphasic computed tomography (CT) in characterizing hyperattenuating adrenal lesions in lung cancer.

METHODS

This retrospective study included 239 patients with lung cancer who underwent adrenal CT for hyperattenuating (> 10 Hounsfield unit) adrenal lesions. Adrenal CT comprised unenhanced and 1-min and 15-min enhanced images. We dichotomized adrenal lesions depending on benign or metastatic lesions. Reference standard for benignity was histologic confirmation or ≥ 6-month stability on follow-up CT. Two independent readers analyzed absolute (APW) or relative percentage wash-out (RPW) using triphasic CT, and enhancement ratio (ER) or percentage wash-in (PWI) using biphasic CT (i.e., unenhanced and 1-min enhanced CT). Criteria for benignity were as follows: criteria 1, (a) APW ≥ 60% or (b) RPW ≥ 40%, and criteria 2, (a) ER > 3 and (b) PWI > 200%. We analyzed area under the curve (AUC) and accuracy for benignity, and inter-reader agreement.

RESULTS

Proportion of benign adrenal lesion was 71.1% (170/239). For criteria 1 and 2, AUCs were 0.872 (95% confidence interval [CI], 0.822-0.911) and 0.886 (95% CI, 0.838-0.923), respectively, for reader 1 (p = 0.566) and 0.816 (95% CI, 0.761-0.863) and 0.814 (95% CI, 0.759-0.862), respectively, for reader 2 (p = 0.955), and accuracies were 87.9% (210/239) and 86.2% (206/239), respectively, for reader 1 (p = 0.479) and 81.2% (194/239) and 80.3% (192/239), respectively, for reader 2 (p = 0.763). Weighted kappa was 0.725 (95% CI, 0.634-0.816) for criteria 1 and 0.736 (95% CI, 0.649-0.824) for criteria 2.

CONCLUSION

Biphasic CT can reliably characterize hyperattenuating adrenal lesions in patients with lung cancer.

KEY POINTS

• Criteria from biphasic computed tomography (CT) for diagnosing benign adrenal lesions were enhancement ratio of > 3 and percentage wash-in of > 200%. • In the analysis by two independent readers, area under the curve between criteria 1 and 2 was not significantly different (0.872 and 0.886 for reader 1; 0.816 and 0.814, for reader 2; p > 0.05 for each comparison). • Wash-in characteristics from biphasic CT are helpful to predict benign adrenal lesions in lung cancer.

Preresection Radiologic Assessment and Imaging Features of 156 Pathologically Proven Adrenal Adenomas

PURPOSE

The aims of the study were to assess the typical and atypical radiologic features of pathologically proven adrenal adenomas and to determine the relationship between the radiologic and histopathologic classification.

METHODS

We retrospectively studied 156 pathologically proven adrenal adenomas in 154 patients from our institutional databases who have computed tomography (CT) and/or magnetic resonance imaging (MRI) examinations before intervention. We determined the histopathologic diagnosis (typical or atypical) using Weiss scoring and classified the adenomas radiologically into typical, atypical, or indeterminate based on lesion size, precontrast CT attenuation, absolute percentage washout, calcification, and necrosis. The κ statistic was used to assess the agreement between radiologists. The Fisher exact test was used to compare the radiologic and pathological classifications.

RESULTS

In consensus, there were 83 typical, 42 atypical, and 31 indeterminate adrenal lesions. Logistic regression model showed that radiologically atypical adenoma was significantly associated with larger size, lobulated shape, higher unenhanced CT attenuation, heterogeneous appearance, nonfunctioning status, absolute percentage washout of less than 60%, and a signal intensity index of less than 16.5%.Pathologically, 147 adenomas were pathologically typical (Weiss 0), and 9 adenomas were pathologically atypical (Weiss 1-2). Radiologically, there was substantial agreement between both readers, with Cohen κ at 0.71. Approximately 98% of radiologically typical adenomas were pathologically typical. Only 17% of radiologically atypical adenomas were pathologically atypical. All radiologically indeterminate adenomas were pathologically typical. However, some of the radiologically indeterminate and typical adenomas still had an atypical component on pathologic analysis, such as necrosis, nuclear atypia, or oncocytic features.

CONCLUSIONS

Radiologically atypical lesion was significantly associated with larger size and higher unenhanced CT attenuation. Approximately 27% of the cases demonstrated atypical features on imaging. Most radiologically atypical adrenal adenomas are pathologically typical.

Adrenocortical hyperplasia: a review of clinical presentation and imaging

Adrenal hyperplasia is non-malignant enlargement of the adrenal glands, which is often bilateral. It can be incidental or related to indolent disease process and may be related to benign or malignant etiologies causing biochemical alterations in the hypothalamic-pituitary-adrenal axis which controls steroidogenesis and in particular cortisol production. Clinical significance of the adrenal hyperplasia is variable ranging from asymptomatic finding to serious manifestations of Cushing syndrome. This is often associated with anatomical changes in the adrenal glands, which typically manifests as diffuse and sometimes nodular enlargement of the adrenal glands radiologically. Approaching adrenal hyperplasia requires careful clinical and biochemical evaluation in correlation with imaging review to differentiate ACTH-dependent and ACTH-independent etiologies. CT is the primary modality of choice for adult adrenal imaging owing to reproducibility, temporal and spatial resolution and broader access, while MRI often serves a complimentary role. Ultrasound and MRI are most commonly used in pediatric cases to evaluate congenital adrenal hyperplasia. This article will discuss the clinical presentation and imaging features of different types and mimics of adrenal cortical hyperplasia.

Mimics, pitfalls, and misdiagnoses of adrenal masses on CT and MRI

Due to the widespread use of imaging, incidental adrenal masses are commonly encountered. A number of pitfalls can result in misdiagnosis of these lesions, including inappropriate choice of imaging technique, presence of pseudolesions, and overlap of imaging features of different adrenal lesions. This article explores the potential pitfalls in imaging of the adrenal glands, on computed tomography and magnetic resonance imaging, that can lead to misinterpretation. Clues to correct diagnoses are provided to evade potential misinterpretation.

Association between Tumor Size and Malignancy Risk in Hormonally Inactive Adrenal Incidentalomas

Introduction

Adrenal incidentalomas (AI) are adrenal masses that are discovered during radiological examinations conducted for other reasons. In this study, we focused on the pathological and radiological properties of nonfunctional AI(NFAI) and the association with malignancy risk in our clinical series.

Methods

A total of 186 patients underwent adrenalectomy between 2010 and 2017; of these, 76 (40.8%) patients with non-functional AI were included in the current study. The radiological and pathologic characteristics of these AIs were retrospectively analyzed to determine the malignancy rate.

Results

There were 22 (28.9%) male and 54 (71.1%) female patients with nonfunctional AI included in this study. The median age was 55 (range: 24-85) years. Of the patients included, 37 (48.6%) had AI on the left and 39 (51.3%) had AI on the right adrenal gland. Sixty-one (80.2%) cases were treated laparoscopically, four (5.3%) required conversion to open surgery due to intraoperative difficulties such as bleeding and adhesions, and 11 (14.4%) were managed with open adrenalectomy. The rate of malignancy in the tumors with diameters of <4 cm, 4-6 cm, and >6 cm was found to be 0%, 2.9%, and 13.6%, respectively.

Conclusions

Determining the ideal cutoff value for surgical indication in an NFAI is challenging. Besides the malignancy risk, the rate of silent pheochromacytomas must be taken into account in the surgical decision.

Minimally Invasive Surgery for Primary and Metastatic Adrenal Malignancy

Since the first description of laparoscopic adrenalectomy (LA) for pheochromocytoma and Cushing syndrome in 1992, the utilization of and indications for a minimally invasive approach to the adrenal gland have vastly expanded. Although minimally invasive adrenalectomy has been established as the preferred approach for patients with benign tumors of the adrenal gland, minimally invasive adrenalectomy for cancer remains controversial. In this article, the authors review the indications for minimally invasive adrenalectomy for adrenal nodules suspicious for, or established to represent, a primary malignancy or a site of metastatic cancer.

Interobserver agreement in distinguishing large adrenal adenomas and adrenocortical carcinomas on computed tomography

PURPOSE

Large adrenal masses pose a diagnostic dilemma. The purpose of this study was twofold: first, to assess the degree of interobserver agreement in evaluating the morphology of pathologically proven adrenal adenomas and adrenocortical carcinomas larger than 4 cm in diameter; and second, to identify morphologic characteristics that correlated with the pathologic diagnosis.

MATERIALS AND METHODS

For this blinded, retrospective study, we collected cases of 25 adrenal adenomas and 33 adrenocortical carcinomas measuring larger than 4 cm. Two radiologists evaluated morphologic characteristics of the lesions on CT. Interobserver agreement was evaluated using kappa statistics, and the correlation of imaging characteristics with the diagnosis was evaluated using a logistic regression model.

RESULTS

We found the highest interobserver agreement in the assessment of precontrast attenuation (Κ = 0.81) as well as substantial agreement in determining the shape and the presence of calcifications (Κ = 0.69 and 0.74, respectively). Readers agreed less often regarding the presence of fat (Κ = 0.48), as well as regarding the presence of necrosis, heterogeneity, and the overall impression (Κ = 0.15, 0.24, and 0.26, respectively). CT characteristics correlated with benignity included round shape (p = 0.02), an overall radiologic impression of a benign lesion (p < 0.0001), the presence of fat (p = 0.01), and a precontrast attenuation of less than 10 Hounsfield units (p < 0.0001). The latter two of these characteristics were highly specific for benign pathology (93% and 100%, respectively).

CONCLUSION

Our study suggests that CT has the ability to consistently identify characteristics significantly correlated with benign vs. malignant adrenal tumors.

Hypokalemia: a clinical update

Hypokalemia is a common electrolyte disturbance, especially in hospitalized patients. It can have various causes, including endocrine ones. Sometimes, hypokalemia requires urgent medical attention. The aim of this review is to present updated information regarding: (1) the definition and prevalence of hypokalemia, (2) the physiology of potassium homeostasis, (3) the various causes leading to hypokalemia, (4) the diagnostic steps for the assessment of hypokalemia and (5) the appropriate treatment of hypokalemia depending on the cause. Practical algorithms for the optimal diagnostic, treatment and follow-up strategy are presented, while an individualized approach is emphasized.

Imaging of Nonmalignant Adrenal Lesions in Children

The adrenal glands in children can be affected by a variety of benign lesions. The diagnosis of adrenal lesions can be challenging, but assessment of morphologic changes in correlation with the clinical presentation can lead to an accurate diagnosis. These lesions can be classified by their cause: congenital (eg, discoid adrenal gland, horseshoe adrenal gland, and epithelial cysts), vascular and/or traumatic (eg, adrenal hemorrhage), infectious (eg, granulomatous diseases), enzyme deficiency disorders (eg, congenital adrenal hyperplasia [CAH] and Wolman disease), benign neoplasms (eg, pheochromocytomas, ganglioneuromas, adrenal adenomas, and myelolipomas), and adrenal mass mimics (eg, extralobar sequestration and extramedullary hematopoiesis). Multimodality cross-sectional imaging helps to define the origin, extent, and relationship of these lesions to adjacent structures, as well as to guide treatment management. The anatomic and functional imaging modalities used to evaluate pediatric adrenal lesions include ultrasonography, computed tomography (CT), magnetic resonance imaging, and iodine 123 metaiodobenzylguanidine scintigraphy. Identifying the imaging features of nonmalignant adrenal lesions is helpful to distinguish these lesions from malignant adrenal neoplasms. Identifying characteristic imaging findings (eg, enlarged adrenal glands, with cerebriform surface, and stippled echogenicity in CAH; a T2-hyperintense mass with avid contrast enhancement in pheochromocytoma; low CT attenuation [<10 HU] and signal intensity drop on opposed-phase chemical shift images in adenoma; and enhancing suprarenal mass supplied by a systemic feeding artery in extralobar sequestration) can aid in making the correct diagnosis. In addition, clinical features (eg, ambiguous genitalia in CAH and hypertension in pheochromocytoma) can also guide the radiologist toward the correct diagnosis. ^©RSNA, 2017.

Adrenocortical carcinoma: Single center experience

Objective

Adrenocortical carcinoma is an aggressive endocrine malignancy with an annual incidence of 0.5-2 cases per million. The most important factors that determine prognosis are tumor stage at the time of diagnosis and the success of surgery. However, advanced age, large tumor size, hormone secretion, high Ki-67 index (>10%), tumor necrosis and high mitotic activity are other factors associated with poor prognosis. In the present study, we aimed to evaluate the contribution of the patient and treatment- related factors to the prognosis in adrenocortical carcinoma.

Material and methods

We included 15 adrenocortical carcinoma patients who were followed in our center between 2005 and 2015. The effects of age, gender, tumor size, type of operation, postoperative resection status and adjuvant treatment on disease-free survival and overall survival were analyzed.

Results

Disease-free survival was 23.32±3.69 months and overall survival was 36.60±10.78 months. Gender, tumor size, tumor stage, type of operation, hormonal activity, presence of necrosis, recurrence and development of metastasis were not found to be associated with disease-free survival and overall survival (p>0.05). Postoperatively applied adjuvant treatments including mitotane, chemotherapy and radiotherapy did not significantly affect disease-free survival in our study, but statistically significant increase in overall survival was observed in patients getting adjuvant treatments (p=0.006).

Conclusion

Adrenocortical carcinoma has poor prognosis and short overall survival, and in its clinical course, recurrence and development of metastasis can be commonly observed even after complete resection of the tumor. Therefore, the patients should be evaluated carefully while determining the surgical procedure during the preoperative period, and the operation and post-operative follow-up should be performed in experienced centers. However, due to the positive effects of adjuvant treatments on survival, all patients should be evaluated postoperatively for the necessity of adjuvant treatments, especially mitotane.