J Korean Soc Radiol.  2019 Nov;80(6):1040-1059. 10.3348/jksr.2019.80.6.1040.

Adrenal Incidentaloma: Imaging Approach and Differential Diagnosis

• Lee MS
• Moon MH
• Sung CK

• KMID: 2464906
• DOI: http://doi.org/10.3348/jksr.2019.80.6.1040

Abstract

Adrenal incidentaloma refers to adrenal masses that are accidentally found on imaging performed for other reasons, without clinical symptoms of adrenal disease. Generally, adrenal masses measuring less than 1 cm are not considered adrenal incidentalomas. The purpose of radiologic examination in evaluating non-functioning adrenal incidentalomas is to distinguish between benign and malignant masses to establish the treatment plan. In this review, based on previously published research and recommendations, we describe the radiologic approach for adrenal incidentaloma and describe the imaging findings of representative diseases.

MeSH Terms

Adrenal Glands
Adrenocortical Adenoma
Diagnosis, Differential*

Figure

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  Fig. 1. Lipid-rich adenoma in the left adrenal gland of a 31-year-old man. A, B. Unenhanced CT shows a 1.3-cm well-defined nodule in the left adrenal gland (A, arrow), with an attenuation value of 7 HU (under 10 HU) (B). HU = Hounsfield unit, SD = standard deviation

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  Fig. 2. Chemical shift imaging. A-C. On unenhanced CT (A) of a 64-year-old man with gastric cancer, a solid mass (arrows) measuring 2.2 cm is observed in the right adrenal gland. The attenuation value is 18.5 HU, which makes it difficult to differentiate between adrenal adenoma and adrenal metastasis. The signal intensity of the right adrenal mass is visually reduced in the opposed-phase image (B) compared to the in-phase image (C). In the quantitative analysis, the adrenal-to-spleen ratio was 0.20, and the signal intensity index was 81.0%. Therefore, the rightadrenal nodule could be diagnosed as adrenal adenoma rather than adrenal metastasis. HU = Hounsfield unit, SD = standard deviation

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  Fig. 3. Calculation of the APW and RPW using adrenal CT of a 29-year-old woman with Cushing's syndrome. A-C. A 2.2-cm well-defined ovoid mass is seen in the left adrenal gland, which was pathologically confirmed as adrenal adenoma. The attenuation values are 15.3, 128.5, and 46.1 in the unenhanced (A), 1-min delayed (B), and 10-min delayed (C) phases, respectively. APW and RPW, which are 72.8% and 64.1%, respectively, are with the reference values (50% and 40%, respectively) for diagnosing adrenal adenoma. APW = absolute percentage washout, RPW = relative percentage washout

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  Fig. 4. Adrenal myelolipoma in the left adrenal gland of a 39-year-old man. Unenhanced CT shows a 7.5-cm well-demarcated round mass, mainly composed of macroscopic fat in the left adrenal gland. The mass had a high-attenuation focus in the anterior portion (41 HU, arrow), suggestive of hemorrhage. The left adrenalectomy specimen revealed thatthe mass was filled with fat and some portion of hemorrhagic necrosis, consistent with myelolipoma.

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  Fig. 5. Adrenal cyst in the left adrenal gland of a 40-year-old man. A, B. On MRI, the masses (arrows) show high signal intensity on the T2-weighted image (A) and low signal intensity on the T1-weighted image (B) without internal soft tissue components or internal enhancement. The presumptive diagnosis was adrenal cyst.

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  Fig. 6. Adrenal hematoma in the right adrenal gland of a 42-year-old man after a traffic accident. A, B. Unenhanced CT (A) shows a 2.5-cm ovoid mass in the right adrenal gland (arrows). On the post-contrast scan (B), the mass shows high attenuation (58 HU) and no enhancement. The final diagnosis was adrenal hemorrhage, considering the history of trauma.

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  Fig. 7. Adrenal hemangioma in the left adrenal gland of a 69-year-old woman. A-C. Unenhanced CT (A) shows a 5.7-cm homogeneous low-attenuation mass in the left adrenal gland. Curvilinear calcification is noted in the mass (arrow). The mass shows peripheral nodular enhancement pattern in the 1-min delayed phase (B) and delayed centripetal enhancement in the 10-min delayed phase (C). The left adrenalectomy specimen revealed that the mass had dilatated vascular networks and dystrophic calcifications, suggestive of hemangioma.

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  Fig. 8. Flowchart for the evaluation of adrenal incidentaloma.

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  Fig. 9. Diffuse large B cell lymphoma in the right adrenal gland of a 42-year-old man. A-C. Unenhanced CT (A) shows an ovoid, homogeneous mass in the right adrenal gland (arrows). Arterial (B) and portal (C) phase scans shows poor homogeneous enhancement and a few cystic foci in the mass. The adrenalectomy specimen was pathologically confirmed as diffuse large B cell lymphoma.

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  Fig. 10. Ganglioneuroma in the right adrenal gland of a 28-year-old woman. A, B. The well-defined ovoid mass in the right adrenal gland shows low signal intensity on the T1-weighted image (A) and heterogeneous high signal intensity on the T2-weighted image (B). Curvilinear low signal intensity foci (arrowheads) are seen in the mass on the T2-weighted image, with whorled appearance. C. Dynamic contrast-enhanced T1-weighted images show slow gradual enhancement because of abundant internal myxoid matrices. Right adrenalectomy was performed, and the mass was pathologically confirmed as ganglioneuroma.

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  Fig. 11. Pheochromocytoma in the left adrenal gland of a 59-year-old man. A-C. Adrenal CT (A, B) shows a well-circumscribed, markedly enhancing round mass (arrows) with areas of necrosis and cystic change in the left adrenal gland. In the MIBG scan (C), the left adrenal mass is very MIBG-avid. The adrenalectomy specimen was pathologically confirmed as pheochromocytoma. MIBG = metaiodobenzylguanidine

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  Fig. 12. Adrenal cortical carcinoma in the right adrenal gland of a 61-year-old man. A, B. A large (9.2 cm) mass is seen in the right adrenal gland. The mass shows high attenuation on the unenhanced image (A) and heterogeneous enhancement after the contrast media injection (B). There are ill-defined central low-attenuation areas, (arrowheads) suggestive of necrosis, and direct invasion with tumor thrombus formation to the adjacent inferior vena cava (arrow).

Reference

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