Evaluation of pharmacokinetics, safety, and efficacy of [211At] meta-astatobenzylguanidine ([211At] MABG) in patients with pheochromocytoma or paraganglioma (PPGL): A study protocol.

BACKGROUND: Pheochromocytoma, or paraganglioma (PPGL), is a tumor that arises from catecholamine-producing chromaffin cells of the adrenal medulla or paraganglion. Systemic therapy, such as the combination of cyclophosphamide, vincristine, and dacarbazine or therapeutic radiopharmaceuticals such as [131I] meta-iodobenzylguanidine (MIBG), may be administered in cases of locally advanced tumors or distant metastases. However, the current therapies are limited in terms of efficacy and implementation. [211At] meta-astatobenzylguanidine (MABG) is an alpha-emitting radionuclide-labeled ligand that has demonstrated remarkable tumor-reducing effects in preclinical studies, and is expected to have a high therapeutic effect on pheochromocytoma cells. METHODS: We are currently conducting an investigator-initiated first-in-human clinical trial to evaluate the pharmacokinetics, safety, and efficacy of [211At] MABG. Patients with locally unresectable or metastatic PPGL refractory to standard therapy and scintigraphically positive [123I] MIBG aggregation are being recruited, and a 3 + 3 dose escalation design was adopted. The initial dose of [211At] MABG is 0.65 MBq/kg, with a dose escalation in a 1:2:4 ratio in each cohort. Dose-limiting toxicity is observed for 6 weeks after a single bolus dose of [211At] MABG, and the patients are observed for 3 months to explore safety and efficacy profiles. The primary endpoint is dose-limiting toxicity to determine both maximum tolerated and recommended doses. The secondary endpoints include radiopharmacokinetics, urinary radioactive excretion rate, urinary catecholamine response rate, objective response rate, progression free survival, [123I] MIBG scintigraphy on reducing tumor accumulation, and quality of life. TRIALS REGISTRATION: jRCT2021220012 registered on 17 June 2022.

CT-based radiomics research for discriminating the risk stratification of pheochromocytoma using different machine learning models: a multi-center study.

OBJECTIVES: The purpose of this study was to explore and verify the value of various machine learning models in preoperative risk stratification of pheochromocytoma. METHODS: A total of 155 patients diagnosed with pheochromocytoma through surgical pathology were included in this research (training cohort: n = 105; test cohort: n = 50); the risk stratification scoring system classified a PASS score of < 4 as low risk and a PASS score of ≥ 4 as high risk. From CT images captured during the non-enhanced, arterial, and portal venous phase, radiomic features were extracted. After reducing dimensions and selecting features, Logistic Regression (LR), Extra Trees, and K-Nearest Neighbor (KNN) were utilized to construct the radiomics models. By adopting ROC curve analysis, the optimal radiomics model was selected. Univariate and multivariate logistic regression analyses of clinical radiological features were used to determine the variables and establish a clinical model. The integration of radiomics and clinical features resulted in the creation of a combined model. ROC curve analysis was used to evaluate the performance of the model, while decision curve analysis (DCA) was employed to assess its clinical value. RESULTS: 3591 radiomics features were extracted from the region of interest in unenhanced and dual-phase (arterial and portal venous phase) CT images. 13 radiomics features were deemed to be valuable. The LR model demonstrated the highest prediction efficiency and robustness among the tested radiomics models, with an AUC of 0.877 in the training cohort and 0.857 in the test cohort. Ultimately, the composite of clinical features was utilized to formulate the clinical model. The combined model demonstrated the best discriminative ability (AUC, training cohort: 0.887; test cohort: 0.874). The DCA of the combined model showed the best clinical efficacy. CONCLUSION: The combined model integrating radiomics and clinical features had an outstanding performance in differentiating the risk of pheochromocytoma and could offer a non-intrusive and effective approach for making clinical decisions.

Cannabinoid hyperemesis and pheochromocytoma hypertensive urgency: a case report.

BACKGROUND: This report presents a case of cannabinoid-induced hyperemesis syndrome causing repeated violent retching in a patient with a large (8 cm) adrenal pheochromocytoma resulting in hypertensive urgency. CASE PRESENTATION: A 69-year-old white male patient with a previously diagnosed pheochromocytoma presented to the emergency department with nausea and vomiting and was found to have hypertensive urgency. Computed tomography scan did not show any acute abdominal pathology and history was inconsistent with a gastrointestinal etiology. Patient had a history of daily cannabinoid use for many years and repeated self-limited hyperemesis episodes, and thus a diagnosis of cannabinoid-induced hyperemesis syndrome was made. It was concluded that the likely explanation for the hypertensive urgency was from physical compression of his adrenal tumor during the episodes of retching resulting in a catecholamine surge. The patient was given antiemetics and admitted to the intensive care unit for blood pressure management. Blood pressure was initially controlled with phentolamine and a clevidipine infusion, then transitioned to oral doxazosin and phenoxybenzamine. Hyperemesis and abdominal pain resolved after 24 hours, and his blood pressure returned to baseline. The patient was discharged with the recommendation to stop all cannabis use. On follow-up, his blood pressure remained well controlled, and he subsequently underwent adrenalectomy for tumor removal. CONCLUSION: Hyperemesis can cause hypertensive events in patients with pheochromocytoma by increasing abdominal pressure, leading to catecholamine release.

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.

Head-to-head comparison between [68Ga]Ga-DOTA-NOC and [18F]DOPA PET/CT in a diverse cohort of patients with pheochromocytomas and paragangliomas.

PURPOSE: To compare the detection ability of 68Ga-labelled DOTA-l-Nal3-octreotide ([68Ga]Ga-DOTA-NOC) and 6-[18F]fluoro-L-3,4-dihydroxyphenylalanine ([18F]DOPA) in patients with phaeochromocytomas and paragangliomas (PPGLs) of different origins and gene mutations, such as germline succinate dehydrogenase complex genes (SDHx). METHODS: Eighty-five patients with histopathologically confirmed PPGLs who underwent both [68Ga]Ga-DOTA-NOC and [18F]DOPA PET/CT from March 2017 to June 2023 were enrolled in this retrospective study. For comparative analyses, PPGLs were classified as phaeochromocytoma (PCC), sympathetic paraganglioma (sPGL), and head/neck paraganglioma (HNPGL). Detection rates were analyzed on per-patient and per-lesion bases and compared using the Chi-square/Fischer's exact test. RESULTS: Among 85 patients with PPGLs (48 males; 43 years ± 17 [SD]), the patient-based detection rates of [68Ga]Ga-DOTA-NOC and [18F]DOPA PET/CT were 87.1% (74/85) and 89.4% (76/85), respectively (p = 0.634), and the lesion-based detection rates were 80.8% (479/593) and 71.2% (422/593), respectively (p < 0.001). Only one patient with a recurrent PCC presented double-negative imaging, while 66 patients exhibited double-positive imaging. The remaining patients were either [68Ga]Ga-DOTA-NOC-negative/[18F]DOPA-positive (n = 10) or [68Ga]Ga-DOTA-NOC-positive/[18F]DOPA-negative (n = 8). In subgroup analyses, [68Ga]Ga-DOTA-NOC PET/CT detected significantly more metastases of sPGL (91.1%, 236/259) and SDHx-related PPGL (89.6%, 86/96) than [18F]DOPA PET/CT (48.6%[126/259] and 50.0%[48/96], respectively; both p < 0.001). However, [18F]DOPA showed significantly higher detection rates of PCC in both primary/recurrent and metastatic lesions (94.3%[50/53] vs. 62.3%[33/53] and 87.9%[174/198] vs. 69.2%[137/198], respectively; both p < 0.001). Regarding metastases in different organs, [68Ga]Ga-DOTA-NOC PET/CT detected more lesions than [18F]DOPA PET/CT in bone (96.2%[176/183] vs. 66.1%[121/183]; p < 0.001) and lymph nodes (82.0%[73/89] vs. 53.9%[48/89]; p < 0.001) but less lesions in peritoneum (20%[4/20] vs. 100%[20/20]; p < 0.001). CONCLUSION: [68Ga]Ga-DOTA-NOC and [18F]DOPA are complementary in diagnosing PPGL under the appropriate clinical setting. [68Ga]Ga-DOTA-NOC should be considered as the ideal first-line tracer for detecting metastases of sPGL and SDHx-related tumours, whereas [18F]DOPA may be the optimal tracer for evaluating non-SDHx-related PCC, especially in detecting primary lesions and monitoring recurrence.

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.

Ensemble Machine Learning Model Incorporating Radiomics and Body Composition for Predicting Intraoperative HDI in PPGL.

CONTEXT: Intraoperative hemodynamic instability (HDI) can lead to cardiovascular and cerebrovascular complications during surgery for pheochromocytoma/paraganglioma (PPGL). OBJECTIVES: We aimed to assess the risk of intraoperative HDI in patients with PPGL to improve surgical outcome. METHODS: A total of 199 consecutive patients with PPGL confirmed by surgical pathology were retrospectively included in this study. This cohort was separated into 2 groups according to intraoperative systolic blood pressure, the HDI group (n = 101) and the hemodynamic stability (HDS) group (n = 98). It was also divided into 2 subcohorts for predictive modeling: the training cohort (n = 140) and the validation cohort (n = 59). Prediction models were developed with both the ensemble machine learning method (EL model) and the multivariate logistic regression model using body composition parameters on computed tomography, tumor radiomics, and clinical data. The efficiency of the models was evaluated with discrimination, calibration, and decision curves. RESULTS: The EL model showed good discrimination between the HDI group and HDS group, with an area under the curve of (AUC) of 96.2% (95% CI, 93.5%-99.0%) in the training cohort, and an AUC of 93.7% (95% CI, 88.0%-99.4%) in the validation cohort. The AUC values from the EL model were significantly higher than the logistic regression model, which had an AUC of 74.4% (95% CI, 66.1%-82.6%) in the training cohort and an AUC of 74.2% (95% CI, 61.1%-87.3%) in the validation cohort. Favorable calibration performance and clinical applicability of the EL model were observed. CONCLUSION: The EL model combining preoperative computed tomography-based body composition, tumor radiomics, and clinical data could potentially help predict intraoperative HDI in patients with PPGL.

177 Lu-DOTATATE in the Treatment of Recurrent Pheochromocytoma With Multiple Metastases.

ABSTRACT: The treatment of metastatic pheochromocytoma is challenging. We report a case of a woman with recurrent pheochromocytoma with multiple metastases who achieved excellent response after 4 cycles of 177 Lu-DOTATATE therapy. She did not experience any observable adverse effects. Her disease was still stable 6 months after the fourth cycle of treatment.

A Prospective Comparative Study of 18 F-FDOPA PET/CT Versus 123 I-MIBG Scintigraphy With SPECT/CT for the Diagnosis of Pheochromocytoma and Paraganglioma.

PURPOSE: This study aimed to compare the diagnostic performances of 18 F-FDOPA PET/CT and 123 I-MIBG scintigraphy with SPECT/CT for detection of pheochromocytoma and paraganglioma (PPGL). PATIENTS AND METHODS: We conducted a prospective, single-institution comparative study. Patients suspected of having PPGL or those showing recurrence and/or distant metastasis of PPGL were enrolled. The primary objective was to affirm the noninferiority of 18 F-FDOPA PET/CT for diagnostic sensitivity. Both 123 I-MIBG scintigraphy with SPECT/CT (at 4 and 24 hours) and 18 F-FDOPA PET/CT (at 5 and 60 minutes after radiotracer administration) were performed. The final diagnosis was established either pathologically or via clinical follow-up. Nuclear physicians, unaware of the clinical data, undertook image analysis. RESULTS: Thirty-two patients were evaluated: 14 of 21 with an initial diagnosis and 9 of 11 with recurrence/metastasis had PPGLs in their final diagnoses. In patient-based analyses, 18 F-FDOPA PET/CT (95.7%) exhibited noninferior sensitivity compared with 123 I-MIBG SPECT/CT (91.3%), within the predetermined noninferiority margin of -12% by a 95% confidence interval lower limit of -10%. Both modalities showed no significant difference in specificity (88.9% vs 88.9%). In the region-based analysis for the recurrence/metastasis group, 18 F-FDOPA PET/CT demonstrated significantly higher sensitivity compared with 123 I-MIBG SPECT/CT (86.2% vs 65.5%, P = 0.031) and superior interobserver agreement (κ = 0.94 vs 0.85). The inclusion of an early phase in dual-phase 18 F-FDOPA PET/CT slightly improved diagnostic performance, albeit not to a statistically significant degree. CONCLUSIONS: 18 F-FDOPA PET/CT demonstrated noninferior sensitivity and comparable specificity to 123 I-MIBG SPECT/CT in the diagnosing PPGL. Notably, in the assessment of PPGL recurrence and metastasis, 18 F-FDOPA PET/CT outperformed 123 I-MIBG SPECT/CT in terms of both sensitivity and interobserver agreement.

Multiple GISTand pheochromocytoma -A rare associationin neurofibromatosis type 1 / GIST múltipley feocromocitoma -Una asociación raraen neurofibromatosis tipo 1

We describe a case of coexistence of multiple gastrointestinal stromal tumors (GIST) and pheochromocytoma in a 32-year-old patient with neurofibromatosis type 1. The coexistence of these two conditions in patients with this syndrome is extremely rare.(AU)

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.

Laparoscopic excision of normotensive variant pheochromocytoma in a case of triple vessel coronary artery disease: The anaesthesia challenge.

Pheochromocytomas are catecholamine-secreting tumours arising mostly from the adrenal medulla. With the advancement in surgical and anaesthetic techniques, the incidence of severe morbidity and mortality associated with surgery is low. However, concurrent coronary artery disease and pheochromocytoma continue to be a challenge due to the risk of adverse cardiovascular events. We describe the successful management of pheochromocytoma excision in a patient with coronary artery disease.

A Novel Technology for 3D-Printing Artificial Vertebral Bodies for Treating Lumbar Spine Adrenal Pheochromocytoma Metastases: A Case Report and Review of the Literature.

BACKGROUND: Pheochromocytoma is an adrenal medullary neuroendocrine tumor that rarely metastasizes to the spine. Currently, its specific treatment methods still present challenges. CASE DESCRIPTION: A 41-year-old male patient who underwent left total adrenalectomy due to pheochromocytoma 3 years ago presented with lower back pain, accompanied by numbness and decreased muscle strength in both legs, as well as decreased sensation. Abnormal transmittance of the L3 vertebral body could be seen on anterior-posterior and lateral lumbar X-rays, irregular bone destruction of the L3 vertebral body was found on CT, and an MRI scan showed that the tumor was located within the L3 vertebral body, protruding into the spinal canal and compressing the epidural sac. No recurrence was found in the abdomen. Preoperatively, perform local embolization of the blood vessels supplying the tumor. First, the L2-3 intervertebral disc, L3-4 intervertebral disc and L3 vertebral body were removed using an anterior approach, the whole tumor was removed, and some of the vertebrae were taken for pathological examination and replaced with a 3D-printed prosthesis. Then, four pedicle screws were placed in the bilateral pedicles of L2 and L4 using the posterior approach, pre-bent connecting rods were installed to replace the bone cortex of the lamina and articular process followed by bone graft fusion of the interlaminar and facet joints. The postoperative results were satisfactory, and there were no perioperative complications. CONCLUSION: Lumbar pheochromocytoma metastasis is rare, difficult to treat, and should be considered in spinal metastases' differential diagnoses so early diagnosis can be made based on medical history and imaging. Preoperative local vascular imaging and embolization of the blood supply vessels were performed. After total en-bloc spondylectomy of the tumor during surgery, a prosthesis was implanted and combined with pedicle screw fixation to reconstruct spinal biomechanical stability, achieving satisfactory results. Therefore, 3D printed artificial vertebral bodies are a good choice for treating adrenal pheochromocytoma lumbar metastasis. The key to successful treatment is close interdisciplinary collaboration in formulating rigorous comprehensive perioperative plans.

Multiple GIST and pheochromocytoma - A rare association in neurofibromatosis type 1.

We describe a case of coexistence of multiple gastrointestinal stromal tumors (GIST) and pheochromocytoma in a 32-year-old patient with neurofibromatosis type 1. The coexistence of these two conditions in patients with this syndrome is extremely rare.

Correlation between the size of pheochromocytoma and the level of metanephrines.

Objective. Pheochromocytomas (PHEO) and paraganglioma (PGLs) are rare neuroendocrine catecholamine-producing tumors that arise from the chromaffin cells of either the adrenal medulla or extra-adrenal paraganglionic tissues. Despite the recent advances in imaging technologies, biochemical evidence of excessive catecholamine production by the tumor is considered the most important test for the diagnosis of these tumors. The aim of the present study is to investigate the role of the catecholamine metabolites (normetanephrine and metanephrine) levels in the diagnosis of PHEO/PGLs and to evaluate if their levels correlate with the size of these tumors. Patients and Methods. Twenty-five patients were included in the study during the time period of 10 years. Their data were compared with another set of 25 patients to obtain the sensitivity and specificity of metanephrine and normetanephrine in the diagnosis of PHEO/PGLs. The tumor size was reviewed in every patient to obtain the correlation coefficient between the tumor sizes and the plasma/24-hour urinary metanephrine levels. Results. The sensitivity and specificity rates for plasma metanephrine were 80-92% and 92-96%, respectively; while for 24-hour urinary metanephrine were 80-90% and 95-100%, respectively. We found a strong positive relationship between the tumor size and the plasma levels of normetanephrine (r=0.518, p<0.01), and metanephrine (r=0.577, p<0.01). While the relation with the 24-hour urinary concentrations of normetanephrine (r=0.384, p=0.01) and 24-h urinary meta-nephrine (r=0.138, p<0.01) was low. Conclusion. The determination of plasma and 24-hour urinary levels of metanephrines is a reliable test for the diagnosis of PHEO, as they are continuously produced by the tumor cells in contrast to catecholamines.

Imaging Pathway of a Pediatric Patient with Succinate Dehydrogenase B-Deficient Paraganglioma.

Pheochromocytoma and paraganglioma are rare in children, at only 1 in every 50,000 cases. Even though some cases are sporadic, they have been connected to syndromes such as von Hippel-Lindau, multiple endocrine neoplasia types IIa and IIb, neurofibromatosis type 1, and hereditary pheochromocytoma-paraganglioma syndromes. A genetic mutation causes around 60% of pheochromocytomas and paragangliomas in children under 18. Methods: A 15-y-old child with a 6-y history of back discomfort is presented. The justification for using 2 functional imaging modalities, 68Ga-DOTATATE PET/CT and 123I-meta-iodobenzylguanidine SPECT/CT, is examined in this case study. We reviewed the patients' journey since the first referral for imaging. Results: Delaying the molecular imaging modalities has affected patients' overall diagnosis and applied treatment outcomes. Conclusion: This case study investigates the potential for the earlier use of various diagnostic modalities in conjunction with diagnostic testing to facilitate an earlier diagnosis. However, since this study is based solely on imaging and lacks access to the patient's clinical or family history, factors such as potential inequities in health-care facilities, health literacy, and socioeconomic status are not addressed. It is essential to acknowledge these influences as they contribute to the inequitable access to health-care settings in New Zealand.

Characterization of indocyanine green fluorescence imaging patterns of pheochromocytomas.

BACKGROUND: Indocyanine green (ICG) fluorescence is a new intraoperative imaging modality for adrenal tumors. Previous work suggested that pheochromocytomas did not show fluorescence, but experience is limited. The objective of this study is to analyze fluorescence imaging patterns of pheochromocytomas. METHODS: This was an IRB-approved retrospective study. Patients who underwent adrenalectomy with ICG imaging were identified from a departmental database. Intraoperative fluorescence patterns were analyzed by reviewing surgical videos. Descriptive and comparative statistical analyses were performed to determine factors associated with different fluorescence patterns of pheochromocytomas. RESULTS: Of the 46 pheochromocytomas included, 50% (n = 23) exhibited fluorescence. Parameters predicting fluorescence on univariate analysis were age, tumor size and hereditary. On multivariate analysis, tumor size was the only predictive parameter of ICG fluorescence, with loss of fluorescence at a threshold of > 3.2 cm (p = 0.004). CONCLUSIONS: This is the largest cohort to date assessing fluorescence properties of pheochromocytomas. In contrast to previous studies, we demonstrated that smaller pheochromocytomas do exhibit fluorescence. This may support the application of intraoperative ICG imaging for smaller or bilateral pheochromocytomas, which may assist in identification and/or cortical-sparing during adrenalectomy.