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Background
Adrenal masses are a common occurrence in clinical practice. Mere detection of these masses is no longer sufficient for management. The advancement of biochemical tests, cross-sectional imaging, and imaging techniques now allow radiologists to characterize a broad range of potential diagnoses. The objective of this presentation is to review a diagnostic algorithm and its imaging features to distinguish and differentiate adrenal incidentalomas, covering a range of pathologies from adenomas to zebras. These principles allow for accelerated diagnosis and treatment, ultimately reducing patient anxieties and biopsies.

Educational Goals / Teaching Points
Given the wide spectrum of potential causes of an incidentaloma, we provide an adrenal imaging algorithm that delineates potential diagnoses. We describe CT and MRI features that guide the diagnosis and management of incidentalomas. The images of a variety of adrenal lesions produced through the adrenal imaging algorithm and cases of rare lesions not captured by the algorithm will be reviewed.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
The diagnostic pathway includes identifying macroscopic appearance and nodule growth, differentiating functional lesions from nonfunctional lesions, application of MRI features, application of CT features, and presentation of a number of rare cases (e.g., pheochromocytoma, lymphoma, adrenal cortical carcinoma). We review the images of a wide range of benign and malignant adrenal lesions. Benign functional lesions of the adrenals included hormone-producing adenomas, pheochromocytomas, cortical hyperplasia, and congenital adrenal hyperplasia. Benign nonfunctional lesions of the adrenals included nonfunctional adenomas, myelolipoma, hematoma, hemangioma, hemorrhage, abscess, endothelial cyst, epithelial cyst, parasitic cyst, neurofibroma, hamartoma, xanthomatosis, amyloidosis, calcification (Wolman disease), extramedullary hematopoiesis, and lymphangioma. Malignant lesions of the adrenals included: metastasis, pheochromocytoma, lymphoma, neuroblastoma, cortical carcinoma, ganglioneuroblastoma, hemangiosarcoma. Adrenal lesions with rare malignant potential included: ganglioneuroma, oncocytoma, schwannoma, collision tumors (adenoma + metastasis or myelolipoma).

Conclusion
Characterization of adrenal incidentalomas using an algorithm offers a practical method for the diagnosis and management of a variety of lesions without necessitating a biopsy and associated morbidities.