Whole-lesion CT histogram analysis as an advanced technique in the portal venous phase: differentiating lipid poor adrenal adenomas from pheochromocytomas

PURPOSE

Adrenal computed tomography (CT) has limitation due to imaging overlaps inthe washout characteristics of pheochromocytomas and adenomas (especially lipid-poor). The aim of this study was to investigate the distinguishability of lipid-poor adrenal adenomas and pheochromocytomas using whole-lesion CT histogram analysis.

MATERIALS AND METHODS

Histopathologically proven 24 lipid-poor adenomas and 29 pheochromocytomas (total 53 lesions in 53 patients) were included in this retrospective study. Data obtained from standard and volumetric examinations of the lesions by dedicated adrenal CT were compared between the two groups using univariate analysis. Parameters that showed differences were further evaluated using multivariate logistic regression analysis.

RESULTS

Univariate analysis revealed significant differences between the two groups in terms of lesion size, lesion volume, percentage of relative wash out, peak HU values and the percentage of voxels with attenuation ≥ 100 HU, ≥ 110 HU and ≥ 120 HU (p = 0.0001, P = 0.0001, P = 0.01, P = 0.008, p = 0.04, p = 0.02, p = 0.02, respectively). Multivariate analysis revealed lesion size ≥ 22.05 mm (OR: 22; p < 0.0001), the percentage of voxels with attenuation ≥ 120 HU being ≥ 9% (OR: 3.27; p = 0.04), peak HU value ≥ 161.5 HU (OR: 4.40; p = 0.01) as risk factors for pheochromocytomas.

CONCLUSIONS

Whole lesion CT histogram analysis can be used to differentiate pheochromocytomas from lipid-poor adenomas. Lesion volume, the percentage of voxels with attenuation ≥ 120 HU and peak HU values are independent parameters that can assist in this differentiation. These findings may help avoid unnecessary biopsies and surgeries for lipid-poor adenomas, while identifying pheochromocytoma risk may improve perioperative patient management. Our results should be validated by future prospective studies.

High Diagnostic Accuracy of Arterial Phase CT in Differentiating Pheochromocytoma in Good/Poor Washout Adrenal Masses

Introduction

Differentiating pheochromocytomas from other adrenal masses based on computed tomography (CT) characteristics remains challenging, particularly in lipid-poor lesions with variable washout patterns. This study evaluated CT features for distinguishing pheochromocytomas in good and poor washout subcohorts.

Methods

We prospectively analyzed 72 patients with unilateral lipid-poor adrenal masses. CT protocol included basal, bolus-tracked arterial, early venous (45 seconds postarterial), and delayed (15 minutes postarterial) phases. Masses were categorized into good and poor washout groups. Histopathology provided the final diagnosis. CT characteristics and calculated indices were compared between pheochromocytomas and other masses in each washout category.

Results

The cohort included pheochromocytomas (n = 35), adrenocortical carcinoma (ACC; n = 15), lipid-poor adenomas (n = 13), and metastatic infiltration/infection (n = 9). In the good washout group, pheochromocytomas (n = 15) showed larger diameters (6.00 vs 3.45 cm, P = .001), higher necrosis frequency (73.3% vs 30%, P = .049), and greater arterial attenuation (173.2 vs 74.5 HU, P < .001) compared to adenomas (n = 9). Arterial attenuation provided a high discriminatory value [area under the curve (AUC): 0.967], with 100% sensitivity at 87.6 Hounsfield unit (HU) and 100% specificity at 139.9 HU. In the poor washout group, pheochromocytomas (n = 20) exhibited higher arterial attenuation (99.2 vs 59.2 HU, P < .001; AUC: 0.844) compared to ACC (n = 14), metastatic infiltration (n = 9), and adenomas (n = 4), with 85% sensitivity and 78% specificity at 73.3 HU. Normetanephrine-secreting/nonsecretory pheochromocytomas showed higher arterial enhancement than metanephrine-secreting ones (132.0 vs 90.5 HU, P = .020) within the poor washout group.

Conclusion

Arterial phase attenuation on CT has good diagnostic accuracy for differentiating pheochromocytomas from other adrenal masses in both good and poor washout categories, potentially guiding hormonal workup.

Diagnostic performance of magnetic resonance imaging features to differentiate adrenal pheochromocytoma from adrenal tumors with positive biochemical testing results

BACKGROUND

It is extremely essential to accurately differentiate pheochromocytoma from Adrenal incidentalomas (AIs) before operation, especially biochemical tests were inconclusive. We aimed to evaluate the value of magnetic resonance imaging (MRI) features to differentiate pheochromocytomas among adrenal tumors, among which the consequences of biochemical screening tests of catecholamines and/or catecholamine metabolites are positive.

METHODS

With institutional review board approval, this study retrospectively compared 35 pheochromocytoma (PHEO) patients with 27 non-pheochromocytoma(non-PHEO) patients between January 2022 to September 2023, among which the consequences of biochemical screening tests of catecholamines and/or catecholamine metabolites are positive. T test was used for the independent continuous data and the chi-square test was used for categorical variables. Univariate and multivariate logistic regression were applied to find the independent variate of the features to differentiate PHEO from non-PHEO and ROC analysis was applied to evaluate the diagnostic value of the independent variate.

RESULTS

We found that the T2-weighted (T2W) signal intensity in patients with pheochromocytoma was higher than other adrenal tumors, with greatly significant (p < 0.001). T2W signal intensity ratio (T2W nodule-to-muscle SI ratio) was an independent risk factor for the differential diagnosis of adrenal PHEOs from non-PHEOs. This feature alone had 91.4% sensitivity and 81.5% specificity to rule out pheochromocytoma based on optimal threshold, with an area under the receiver operating characteristics curve (AUC‑ROC) of 0.910(95% C I: 0.833-0.987).

CONCLUSION

Our study confirms that T2W signal intensity ratio can differentiate PHEO from non-PHEO, among which the consequences of biochemical screening tests of catecholamines and/or catecholamine metabolites are positive.

Imaging of Pheochromocytomas and Paragangliomas

Pheochromocytomas/paragangliomas are unique in their highly variable molecular landscape driven by genetic alterations, either germline or somatic. These mutations translate into different clusters with distinct tumor locations, biochemical/metabolomic features, tumor cell characteristics (eg, receptors, transporters), and disease course. Such tumor heterogeneity calls for different imaging strategies in order to provide proper diagnosis and follow-up. This also warrants selection of the most appropriate and locally available imaging modalities tailored to an individual patient based on consideration of many relevant factors including age, (anticipated) tumor location(s), size, and multifocality, underlying genotype, biochemical phenotype, chance of metastases, as well as the patient's personal preference and treatment goals. Anatomical imaging using computed tomography and magnetic resonance imaging and functional imaging using positron emission tomography and single photon emission computed tomography are currently a cornerstone in the evaluation of patients with pheochromocytomas/paragangliomas. In modern nuclear medicine practice, a multitude of radionuclides with relevance to diagnostic work-up and treatment planning (theranostics) is available, including radiolabeled metaiodobenzylguanidine, fluorodeoxyglucose, fluorodihydroxyphenylalanine, and somatostatin analogues. This review amalgamates up-to-date imaging guidelines, expert opinions, and recent discoveries. Based on the rich toolbox for anatomical and functional imaging that is currently available, we aim to define a customized approach in patients with (suspected) pheochromocytomas/paragangliomas from a practical clinical perspective. We provide imaging algorithms for different starting points for initial diagnostic work-up and course of the disease, including adrenal incidentaloma, established biochemical diagnosis, postsurgical follow-up, tumor screening in pathogenic variant carriers, staging and restaging of metastatic disease, theranostics, and response monitoring.

Validation of the modified CT criteria for identifying non-adenomas

PURPOSE

Although adrenal computed tomography (CT) percentage washout is a potentially powerful imaging technique for differentiating adrenal adenomas from non-adenomas, its application to non-adenomas can be problematic. Recently, modified criteria for diagnosing pheochromocytomas using adrenal CT were developed based on data from 199 patients with surgically proven pheochromocytomas and adenomas. However, these criteria have not been thoroughly validated. The purpose of this study was to validate the performance of the modified criteria for diagnosing non-adenomas including pheochromocytomas.

METHODS

The conventional and modified criteria were applied to 266 patients from two cohorts who had surgically proven lipid-poor adenomas (155/266, 58.3%) and non-adenomas (111/266, 41.7%) and underwent adrenal CT. Two radiologists calculated the attenuation on each dynamic phase and percentage washout of adrenal masses. The final assessments based on the conventional and modified criteria were categorized into adenomas or non-adenomas. The diagnostic performance of each criterion for diagnosing non-adenomas was evaluated using the area under the receiver operating characteristic curve (AUC). False negatives and positives were also compared.

RESULTS

The AUC for the diagnosis of non-adenomas was 0.806 for conventional criteria and 0.858 for modified criteria (p = 0.047). The false-negative rate of conventional criteria for the diagnosis of non-adenomas was 29.7%. Use of modified criteria could have reduced the false-negative rate by to 7.2%. The false-positive rate increased from 9% to 21.3% when using the modified criteria.

CONCLUSION

The utilization of modified criteria has the potential to identify additional non-adenomas that would otherwise be misdiagnosed as adenomas using conventional criteria alone.

Anastomosing haemangioma of the adrenal gland: A clinicopathological series of seven cases

AIMS

Anastomosing haemangioma is a rare benign vascular neoplasm that may histologically mimic angiosarcoma. We report the largest single institution series of anastomosing haemangioma in the adrenal gland with emphasis on clinical and radiological features.

METHODS AND RESULTS

Our laboratory information system was searched for a 25-year period (1999-2023), yielding seven cases confirmed as anastomosing haemangioma of the adrenal gland after pathological re-review. Clinical, radiological and pathological information was obtained from medical charts and submitting pathologists. Of a total of seven patients, four (57.1%) were men and three women, ranging in age from 37 to 75 years (mean = 61). Six of seven patients underwent adrenalectomies and one had radical nephrectomy. Tumours ranged from 0.7 to 6.4 cm (mean = 2.1 cm) and five of seven (71%) were grossly well-circumscribed. Five of seven lesions were found incidentally at imaging for other indications. All tumours were unifocal except one, which presented with multifocal disease with a concurrent adjacent retroperitoneal anastomosing haemangioma. Three of five tumours imaged with contrast enhancement were almost completely hyperenhancing with a small central non-enhancing portion, features overlapping with pheochromocytoma. One of seven tumours involved the peri-adrenal adipose tissue with a focally infiltrative pattern. There were no recurrences or metastases in six patients with available follow-up data (median = 95 months).

CONCLUSIONS

Benign anastomosing haemangiomas of the adrenal gland tend to occur in older patients, may mimic pheochromocytoma on imaging and must be distinguished from angiosarcoma pathologically. Better awareness of this entity by pathologists, radiologists and surgeons is crucial to appropriate work-up, diagnosis and management.

Machine learning for differentiation of lipid-poor adrenal adenoma and subclinical pheochromocytoma based on multiphase CT imaging radiomics

BACKGROUND

There is a paucity of research investigating the application of machine learning techniques for distinguishing between lipid-poor adrenal adenoma (LPA) and subclinical pheochromocytoma (sPHEO) based on radiomic features extracted from non-contrast and dynamic contrast-enhanced computed tomography (CT) scans of the abdomen.

METHODS

We conducted a retrospective analysis of multiphase spiral CT scans, including non-contrast, arterial, venous, and delayed phases, as well as thin- and thick-thickness images from 134 patients with surgically and pathologically confirmed. A total of 52 patients with LPA and 44 patients with sPHEO were randomly assigned to training/testing sets in a 7:3 ratio. Additionally, a validation set was comprised of 22 LPA cases and 16 sPHEO cases from two other hospitals. We used 3D Slicer and PyRadiomics to segment tumors and extract radiomic features, respectively. We then applied T-test and least absolute shrinkage and selection operator (LASSO) to select features. Six binary classifiers, including K-nearest neighbor (KNN), logistic regression (LR), decision tree (DT), random forest (RF), support vector machine (SVM), and multi-layer perceptron (MLP), were employed to differentiate LPA from sPHEO. Receiver operating characteristic (ROC) curves and area under the curve (AUC) values were compared using DeLong's method.

RESULTS

All six classifiers showed good diagnostic performance for each phase and slice thickness, as well as for the entire CT data, with AUC values ranging from 0.706 to 1. Non-contrast CT densities of LPA were significantly lower than those of sPHEO (P < 0.001). However, using the optimal threshold for non-contrast CT density, sensitivity was only 0.743, specificity 0.744, and AUC 0.828. Delayed phase CT density yielded a sensitivity of 0.971, specificity of 0.641, and AUC of 0.814. In radiomics, AUC values for the testing set using non-contrast CT images were: KNN 0.919, LR 0.979, DT 0.835, RF 0.967, SVM 0.979, and MLP 0.981. In the validation set, AUC values were: KNN 0.891, LR 0.974, DT 0.891, RF 0.964, SVM 0.949, and MLP 0.979.

CONCLUSIONS

The machine learning model based on CT radiomics can accurately differentiate LPA from sPHEO, even using non-contrast CT data alone, making contrast-enhanced CT unnecessary for diagnosing LPA and sPHEO.

An Integrated CT and MRI Imaging Model to Differentiate between Adrenal Adenomas and Pheochromocytomas

PURPOSE

to perform an external validation of our predictive model to rule out pheochromocytoma (PHEO) based on unenhanced CT in a cohort of patients with PHEOs and adenomas who underwent adrenalectomy.

METHODS

The predictive model was previously developed in a retrospective cohort of 1131 patients presenting with adrenal lesions. In the present study, we performed an external validation of the model in another cohort of 214 patients with available histopathological results.

RESULTS

For the external validation, 115 patients with PHEOs and 99 with adenomas were included. Our previously described predictive model combining the variables of high lipid content and tumor size in unenhanced CT (AUC-ROC: 0.961) had a lower diagnostic accuracy in our current study population for the prediction of PHEO (AUC: 0.750). However, when we excluded atypical adenomas (with Hounsfield units (HU) > 10, n = 39), the diagnostic accuracy increased to 87.4%. In addition, in the whole cohort (including atypical adenomas), when MRI information was included in the model, the diagnostic accuracy increased to up to 85% when the variables tumor size, high lipid content in an unenhanced CT scan, and hyperintensity in the T2 sequence in MRI were included. The probability of PHEO was <0.3% for adrenal lesions <20 mm with >10 HU and without hyperintensity in T2.

CONCLUSION

Our study confirms that our predictive model combining tumor size and lipid content has high reliability for the prediction of PHEO when atypical adrenal lesions are excluded. However, for atypical adrenal lesions with >10 HU in an unenhanced CT scan, MRI information is necessary for a proper exclusion of the PHEO diagnosis.

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.

Lexicon for adrenal terms at CT and MRI: a consensus of the Society of Abdominal Radiology adrenal neoplasm disease-focused panel

PURPOSE

Substantial variation in imaging terms used to describe the adrenal gland and adrenal findings leads to ambiguity and uncertainty in radiology reports and subsequently their understanding by referring clinicians. The purpose of this study was to develop a standardized lexicon to describe adrenal imaging findings at CT and MRI.

METHODS

Fourteen members of the Society of Abdominal Radiology adrenal neoplasm disease-focused panel (SAR-DFP) including one endocrine surgeon participated to develop an adrenal lexicon using a modified Delphi process to reach consensus. Five radiologists prepared a preliminary list of 35 imaging terms that was sent to the full group as an online survey (19 general imaging terms, 9 specific to CT, and 7 specific to MRI). In the first round, members voted on terms to be included and proposed definitions; subsequent two rounds were used to achieve consensus on definitions (defined as ≥ 80% agreement).

RESULTS

Consensus for inclusion was reached on 33/35 terms with two terms excluded (anterior limb and normal adrenal size measurements). Greater than 80% consensus was reached on the definitions for 15 terms following the first round, with subsequent consensus achieved for the definitions of the remaining 18 terms following two additional rounds. No included term had remaining disagreement.

CONCLUSION

Expert consensus produced a standardized lexicon for reporting adrenal findings at CT and MRI. The use of this consensus lexicon should improve radiology report clarity, standardize clinical and research terminology, and reduce uncertainty for referring providers when adrenal findings are present.

Subclinical phaeochromocytoma: a diagnostic and management challenge

There is a paradigm shift in the detection of phaeochromocytomas with more being identified as adrenal 'incidentalomas'. While majority of these individuals are asymptomatic, they are nevertheless at risk of subtle cardiovascular dysfunction and phaeochromocytoma crises. Therefore, early resection of phaeochromocytomas, even if subclinical, is recommended. However, the perioperative management can be challenging as the normotension can limit the initiation and titration of alpha-blockade. We present a man in his 60s with a subclinical phaeochromocytoma, discuss the evaluation of an incidentally discovered adrenal nodule, as well as the practical considerations in the perioperative management.

Predictive model of pheochromocytoma based on the imaging features of the adrenal tumours

The purpose of our study was to develop a predictive model to rule out pheochromocytoma among adrenal tumours, based on unenhanced computed tomography (CT) and/or magnetic resonance imaging (MRI) features. We performed a retrospective multicentre study of 1131 patients presenting with adrenal lesions including 163 subjects with histological confirmation of pheochromocytoma (PHEO), and 968 patients showing no clinical suspicion of pheochromocytoma in whom plasma and/or urinary metanephrines and/or catecholamines were within reference ranges (non-PHEO). We found that tumour size was significantly larger in PHEO than non-PHEO lesions (44.3 ± 33.2 versus 20.6 ± 9.2 mm respectively; P < 0.001). Mean unenhanced CT attenuation was higher in PHEO (52.4 ± 43.1 versus 4.7 ± 17.9HU; P < 0.001). High lipid content in CT was more frequent among non-PHEO (83.6% versus 3.8% respectively; P < 0.001); and this feature alone had 83.6% sensitivity and 96.2% specificity to rule out pheochromocytoma with an area under the receiver operating characteristics curve (AUC-ROC) of 0.899. The combination of high lipid content and tumour size improved the diagnostic accuracy (AUC-ROC 0.961, sensitivity 88.1% and specificity 92.3%). The probability of having a pheochromocytoma was 0.1% for adrenal lesions smaller than 20 mm showing high lipid content in CT. Ninety percent of non-PHEO presented loss of signal in the “out of phase” MRI sequence compared to 39.0% of PHEO (P < 0.001), but the specificity of this feature for the diagnosis of non-PHEO lesions low. In conclusion, our study suggests that sparing biochemical screening for pheochromocytoma might be reasonable in patients with adrenal lesions smaller than 20 mm showing high lipid content in the CT scan, if there are no typical signs and symptoms of pheochromocytoma.

Is it Possible to Assess the Functional Status of Hormone Secretion or Non- Secretion of Adrenal Masses Through Their Magnetic Resonance Imaging (MRI) Characteristics?

BACKGROUND

Diagnostic imaging techniques, including magnetic resonance imaging (MRI) should be performed on all patients with incidentalomas. However, limited number of studies on whether the quantitative measurements (signal intensity index, adrenal to spleen ratio) in MRI could predict the functional status of adrenal adenomas are available.

METHODS

Between 2015-2020, 404 patients (265 females, 139 males) with adrenal mass who were referred to the university hospital for further investigation were included. After detailed diagnostic hormonal evaluation, all patients were examined with the MRI 1.5 T device (Signa, GE Medical Systems; Milwaukee, USA). The signal intensities of the adrenal lesions on T2W images were qualitatively evaluated and noted as homogenous or heterogeneous in comparison with the liver signal intensity (SI). A chemical-shift SI index and chemical shift adrenal-to-spleen SI ratio were also calculated.

RESULTS

While 331(81.9%) of the patients had nonfunctional adrenal mass, the rest (n=73, 18.1%) were patients with functional (autonomous cortisol secretion-ACS, Cushing syndrome-CS, pheochromocytoma, primary hyperaldosteronism-PA) adrenal masses. In phase vs. phase values of patients with NFAI, Pheo(n=17), ACS (n=30), CS (n=11), and PA (n=15) were 474.04±126.7 vs. 226.6±132.4, 495.3±182.8 vs. 282.17±189.1, 445.2±134.8 vs. 203.3±76.2, 506.8±126.5 vs. 212.2±73.6 and 496.2±147.5 vs. 246.6±102.1, respectively. Mean signal intensity index (SII) and adrenal to spleen ratio (ASR) of all groups (NFAI, Pheo, ACS, CS, PA) were 52.0±24.8 and 0.51, 44.9±22.5 and 0.55, 49.5±24.5 and 0.53, 56.2±16.4 and 0.43, 47.6±25.1 and 0.54, respectively. Based on the currently accepted measurements in the case of ASR and SII, all lesions were similar and observed as fat rich adenomas (p*= 0.552, p** = 0.45).

CONCLUSION

The quantitative assessment (SII, ASR) of intracellular lipids in an incidentally discovered adrenal tumor could only help distinguish adrenal masses in the case of adenomas or non-adenomas. As an initial diagnostic evaluation, clinical and laboratory assessment to distinguish hormone secretion should be done for all patients with adrenal incidentalomas.

Differentiation of lipid-poor adenoma from pheochromocytoma on biphasic contrast-enhanced CT

PURPOSE

To evaluate the diagnostic performance of biphasic contrast-enhanced CT in differentiation of lipid-poor adenomas from pheochromocytomas.

METHODS

129 patients with 132 lipid-poor adenomas and 93 patients with 97 pheochromocytomas confirmed by pathology were included in this retrospective study. Patients underwent unenhanced abdominal CT scan followed by arterial and venous phase. Quantitative and qualitative imaging features were compared between the two groups using univariate analysis. Risk factors for pheochromocytomas were evaluated by multivariate logistic regression analysis and a diagnostic scoring model was established based on odd ratio (OR) of the risk factors.

RESULTS

Pheochromocytomas were larger and showed cystic degeneration more frequently compared with lipid-poor adenomas (p < 0.01). No significant difference was found in peak enhancement phase between the two groups (p = 0.348). Attenuation values on unenhanced phase (CTU), arterial phase (CTA), and venous phase (CTV) of pheochromocytomas were significantly higher than that of lipid-poor adenomas while enhancement ratio on arterial and venous phase (ERA, ERV) of pheochromocytomas was significantly lower than that of lipid-poor adenomas (all p < 0.05). Multivariate analysis revealed lesion size > 29 mm (OR: 5.74; 95% CI 2.51-13.16; p < 0.001), CTA > 81 HU (OR: 2.54; 95% CI 1.04-6.17; p = 0.04), CTV > 97 HU (OR: 11.19; 95% CI 3.21-38.97; p < 0.001), ERV ≤ 1.5 (OR: 20.23; 95% CI 6.30-64.87; p < 0.001), and the presence of cystic degeneration (OR: 6.22, 95% CI 1.74-22.25; p = 0.005) were risk factors for pheochromocytomas. The diagnostic scoring model yielded an area under the curve (AUC) of 0.911.

CONCLUSIONS

Biphasic contrast-enhanced CT showed good diagnostic performance in differentiation of lipid-poor adenomas from pheochromocytomas.

Relative Enhancement Ratio of Portal Venous Phase to Unenhanced CT in the Diagnosis of Lipid-poor Adrenal Adenomas

Background The development of an accurate, practical, noninvasive, and widely available diagnostic approach to characterize lipid-poor adrenal lesions (greater than 10 HU at unenhanced CT) remains an ongoing demand. Purpose To investigate whether combined assessment of unenhanced and portal venous phase CT allows for the differentiation of lipid-poor adrenal adenomas from nonadenomas. Materials and Methods Patients with lipid-poor adrenal lesions who underwent unenhanced and portal venous phase CT with a single-energy scanner between January 2016 and March 2020 were identified retrospectively. For each lesion, the unenhanced and contrast-enhanced attenuation were measured; the absolute enhancement (contrast-enhanced minus unenhanced attenuation [HU]) and relative enhancement ratio ([absolute enhancement divided by unenhanced attenuation] × 100%) were calculated. The sensitivity achieved at 95% specificity to distinguish adenomas from nonadenomas was determined with receiver operating characteristic curve analysis and compared among parameters with use of the McNemar test. Results A total of 220 patients (mean age ± standard deviation, 66 years ± 12; 134 men) with 131 lipid-poor adenomas and 89 nonadenomas were analyzed. The sensitivity (achieved at 95% specificity) of the relative enhancement ratio (86% [113 of 131 adenomas; 95% CI: 79, 92] at a threshold of >210%) was higher than that of unenhanced attenuation (50% [66 of 131 adenomas; 95% CI: 42, 59] at a threshold of ≤21 HU), contrast-enhanced attenuation (3% [four of 131 adenomas; 95% CI: 1, 8] at a threshold of >120 HU), and absolute enhancement (24% [32 of 131 adenomas; 95% CI: 17, 33] at a threshold of >74 HU; all P < .001). The sensitivities of the relative enhancement ratio were 100% (58 of 58 adenomas; 95% CI: 94, 100), 83% (52 of 63 adenomas; 95% CI: 71, 91), and 30% (three of 10 adenomas; 95% CI: 7, 65) for adenomas measuring unenhanced attenuation of more than 10 HU up to 20 HU, 21-30 HU, and more than 30 HU, respectively. Conclusion A relative enhancement ratio threshold of greater than 210%, measured at unenhanced and portal venous phase CT, accurately differentiated lipid-poor adenomas from nonadenomas, particularly for lesions with unenhanced attenuation of 10-30 HU. © RSNA, 2021 Online supplemental material is available for this article.

COX4I2 is a novel biomarker of blood supply in adrenal tumors

Background

Previous study has been reported that COX4I2 expression level demonstrated a positive correlation with microvessel density in pheochromocytomas (PCC) samples, suggesting that the expression of COX4I2 maybe related to blood supply level in other adrenal tumors as well. The aim of this study is to clarify the correlation of COX4I2 expression and blood supply in adrenal tumors.

Methods

A total of 84 patients were recruited, among which 46 was diagnosed as adrenocortical adenoma (ACA) and 38 was diagnosed as PCC. Contrast-enhanced CT values were used to evaluate the blood supply levels in those patients. The expression of mRNA was examined by quantitative real-time polymerase chain reaction (qPCR) and protein was detected by immunohistochemistry (IHC).

Results

The COX4I2 expression level in PCC group is significantly higher than that in ACA group (P<0.01). The expression of angiogenesis-related genes EPAS1, VEGFA and KDR mRNA in PCC group is higher than that of ACA group (P<0.05). Correlation analysis shows COX4I2 expression level is correlated with CT values (P<0.001), intraoperative blood loss (P<0.05) and operation time (P<0.05), and the expression of COX4I2 mRNA is correlated with EPAS1, VEGFA and KDR mRNA (P<0.01).

Conclusions

The results displayed a distinct expression level of COX4I2 between ACA and PCC, suggesting that COX4I2 is a novel biomarker of blood supply in adrenal tumors. This research also opens the possibility for further research on COX4I2 as a novel target for anti-tumor angiogenesis.

Imaging of Pheochromocytoma and Paraganglioma

Imaging plays a critical role in the management of pheochromocytomas and paragangliomas and often guides treatment. The discovery of susceptibility genes associated with these tumors has led to better understanding of clinical and imaging phenotypes. Functional imaging is of prime importance because of its sensitivity and specificity in subtypes of pheochromocytoma and paraganglioma. Several radiopharmaceuticals have been developed to target specific receptors and metabolic processes seen in pheochromocytomas and paragangliomas, including 131I/123I-metaiodobenzylguanidine, 6-18F-fluoro-l-3,4-dihydroxyphenylalanine, 18F-FDG, and 68Ga-DOTA-somatostatin analogs. Two of these have consequently been adapted for therapy. This educational review focuses on the current imaging approaches used in pheochromocytomas and paragangliomas, which vary among clinical and genotypic presentations.

Distinguishing pheochromocytoma from adrenal adenoma by using modified computed tomography criteria

PURPOSE

To investigate the performance of modified criteria to distinguish pheochromocytoma from adrenal adenoma by using adrenal protocol computed tomography (CT).

METHODS

We retrospectively included consecutive 199 patients who underwent adrenal CT and surgically proven pheochromocytoma (n = 66) or adenoma (n = 133). Two independent radiologists analyzed two CT criteria for pheochromocytoma. Conventional criteria were as follows: (a) lesion attenuation on unenhanced CT > 10 Hounsfield unit (HU); (b) absolute percentage washout < 60%; and (c) relative percentage washout < 40%. Modified criteria were as follows: (a) conventional criteria or (b) one of the following findings: (i) lesion attenuation on unenhanced CT ≥ 40 HU, (ii) 1-min enhanced CT ≥ 160 HU, (iii) 15-min enhanced CT ≥ 70 HU, , or (iv) intralesional cystic degeneration seen on both 1-min and 15-min enhanced CT. We analyzed area under the curve (AUC) and inter-reader agreement.

RESULTS

Proportion of pheochromocytoma was 33.2% (66/199). AUC of modified criteria was consistently higher than that of conventional criteria for distinguishing pheochromocytoma from adenoma (reader 1, 0.864 versus 0.746 for raw data set and 0.865 versus 0.746 for internal validation set; reader 2, 0.872 versus 0.758 for raw data set and 0.872 versus 0.757 for internal validation set) (p < 0.05 for all comparisons). Inter-reader agreement was excellent in interpreting any criteria (weighted kappa > 0.800).

CONCLUSION

Our modified criteria seem to improve diagnostic performance of adrenal CT in distinguishing pheochromocytoma from adrenal adenoma.

A Critical Analysis of Computed Tomography Washout in Lipid-Poor Adrenal Incidentalomas

BACKGROUND

Contrast-enhanced computed tomography (CT) with washout has emerged as an option to distinguish lipid-poor adenomas from non-adenomas.

OBJECTIVE

The aim of this study was to assess the utility of CT washout in characterizing indeterminate lipid-poor adrenal incidentalomas.

METHODS

From an Institutional Review Board-approved database, patients with adrenal incidentalomas who had adrenal protocol CT scans with a 15-min washout between 2003 and 2019 were identified. Non-contrast CT attenuation and washout patterns of different tumor types were compared.

RESULTS

Overall, 156 patients with 175 adrenal lesions were included. Average tumor size was 3.0 cm, non-contrast CT density was 24.7 Hounsfield units (HU), and absolute washout was 52.6%. In 102 lesions (58.3%), CT washout was ≥ 60%; 94 (92.2%) of these were benign adrenocortical adenomas, 7 (6.9%) were pheochromocytomas, and 1 (0.9%) was an adrenal hematoma. Furthermore, in 73 tumors (41.7%), CT washout was < 60%; diagnosis was benign adrenocortical adenoma in 45 (61.6%) lesions, pheochromocytoma in 8 (11%) lesions, metastasis in 9 (12.3%) lesions, adrenocortical cancer in 6 (8.2%) lesions, and 'others' in 5 (6.9%) lesions. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of  > 60% absolute CT washout for detecting an adrenal adenoma was 67.6%, 77.8%, 92.2%, 38.4%, and 69.7%, respectively.

CONCLUSION

CT washout should be incorporated into the management algorithm of indeterminate adrenal incidentalomas with a high non-contrast CT attenuation to 'rule-in' benign tumors. For small tumors with mild elevation of plasma metanephrines, it should be kept in mind that adenomas and pheochromocytomas may have similar imaging and washout characteristics.

Diagnostic performance of adrenal CT in the differentiation of adenoma and pheochromocytoma

BACKGROUND

Differentiation of adenoma and pheochromocytoma on computed tomography (CT) may be problematic.

PURPOSE

To investigate if adenoma and pheochromocytoma can be differentiated with adrenal CT.

MATERIAL AND METHODS

A total of 147 pathologically proven adrenal masses (119 adenomas, 28 pheochromocytomas) that had undergone adrenal CT were retrospectively evaluated. Lesion attenuation on unenhanced phase (UEP), portal phase (PP), 15-min delayed phase (DP), absolute/relative percentage enhancement wash-out (APEW/RPEW), and qualitative features were recorded. Student's t-test for parametric data, Mann-Whitney U test for non-parametric data, and Fisher's exact test for categorical data were used. Diagnostic performance of CT attenuation was assessed by area under the curve (AUC) of the receiver operating characteristics.

RESULTS

APEW of adenomas was not significantly different from pheochromocytomas; 68.4% and 59% (P = 0.284). Adenomas had significantly higher RPEW; 57.3% vs. 37.4% (P = 0.004). Of pheochromocytomas, 50% met APEW >60% or RPEW >40% criteria, and therefore were misclassified as adenoma on wash-out CT. Of those, 80% (4/5) were < 3 cm. UEP, PP, and DP attenuations of pheochromocytomas were significantly higher than adenomas; however, they were overlapping. AUC for UEP, PP, and DP was 0.906, 0.784, and 0.926, respectively. Larger pheochromocytomas were more likely to contain necrosis compared to smaller pheochromocytomas and adenomas; 41.6% vs. 12.5% vs. 3%. Homogeneous enhancement was seen in 25% of pheochromocytomas and 49% of adenomas (P = 0.018). No significant difference was found in terms of lesion borders and presence of fat/calcification (P > 0.05).

CONCLUSIONS

A considerable percentage of pheochromocytomas, especially smaller ones, demonstrate adenoma-like wash-out on CT. Heterogeneous enhancement, higher attenuation, and necrosis are more suggestive of pheochromocytoma.

Characteristic CT features of pheochromocytomas - probability model calculation tool based on a multicentric study

OBJECTIVES

The aim of the study was to evaluate the CT features of adrenal tumors in an effort to identify features specific to pheochromocytomas and second, to define a feasible probability calculation model.

METHODS

This multicentric retrospective study included patients from the period 2003 to 2017 with an appropriate CT examination and a histological diagnosis of an adrenal adenoma, pheochromocytoma, adrenocortical carcinoma, or metastasis. In total, 346 patients were suitable for the CT image analysis, which included evaluation of the largest diameter, the shape of the lesion, the presence of central necrosis and its margins, and the presence of an enhancing peripheral rim ("ring sign").

RESULTS

Pheochromocytomas have a significantly more spherical shape (P<0.001), whereas an elliptical shape significantly reduces the probability of a pheochromocytoma (odds ratio = 0.015), as does another shape (odds ratio = 0.006). A "ring sign" is also more frequent in pheochromocytomas compared to other adrenal tumors (P=0.001, odds ratio = 6.49). A sharp necrosis also increases the probability of a pheochromocytoma more than unsharp necrosis (odds ratio 231.6 vs. 20.2). The probability calculation model created on the basis of the results confirms a high sensitivity and specificity (80% and 95%).

CONCLUSION

This study confirms the value of anatomical features in the assessment of adrenal masses with the ability to significantly improve the identification of pheochromocytomas. Advanced assessment of the tumor shape was defined and a original comprehensive calculating tool of the pheochromocytoma probability was created on the basis of the results presented here and could be used in clinical routine.