Adrenal Lesions: A Review of Imaging

Abstract

Adrenal lesions are frequently incidentally diagnosed during investigations for other clinical conditions. Despite being usually benign, nonfunctioning, and silent, they can occasionally cause discomfort or be responsible for various clinical conditions due to hormonal dysregulation; therefore, their characterization is of paramount importance for establishing the best therapeutic strategy. Imaging techniques such as ultrasound, computed tomography, magnetic resonance, and PET-TC, providing anatomical and functional information, play a central role in the diagnostic workup, allowing clinicians and surgeons to choose the optimal lesion management. This review aims at providing an overview of the most encountered adrenal lesions, both benign and malignant, including describing their imaging characteristics.

Keywords: adenoma; adrenal; computed tomography; incidentaloma; myelolipoma.

Figure 1

Adrenal adenoma in a 63-year-old woman. Unenhanced CT (a) shows a 2 cm left adrenal lipid rich adenoma (yellow arrow) characterized by attenuation values lower than 10 HU. Axial T1-weighted in-phase (b) and out-of-phase (c) MR images demonstrate a signal loss in the out-of-phase images (white arrow).

Figure 2

Adrenal myelolipoma in a 42-year-old woman. CT demonstrates a large mass within the left adrenal gland (white arrow in (a,b) and yellow arrows in (c,d)), characterized by well-defined borders and internal inhomogeneity. Axial unenhanced CT (a) shows attenuation values <−30 HU due to the presence of gross fat. On portal venous phase (b), the mass shows subtle enhancement due to its poor vascularization. Coronal T2 fat sat sequence (c) and axial T1-weighted out-phase image (d) demonstrate extracellular fat.

Figure 3

Axial unenhanced CT (a) and coronal reformatted portal venous phase of contrast-enhanced CT (b) of a 65-year-old man with bilateral adrenal hyperplasia. Note the symmetrical bilateral thickening of adrenal glands, presenting normal contours and no mass lesions.

Figure 4

A 33-year-old female with an incidental left adrenal cyst. MR revealed a 4 cm nodular lesion in the left adrenal gland characterized by thin walls and high and homogeneous signal in T2 (a) and T2 fat-sat sequences (b). T1 signal (c,d) is in accordance with simple fluid content, and DWI/ADC sequence (e,f) does not show signs of hypercellularity.

Figure 5

A 65-year-old female with right adrenal pheochromocytoma. CT axial arterial (a) and portal venous phases (b,c) show inhomogeneous adrenal solid lesion with strong and heterogeneous enhancement; the lesion showed an absolute wash-out of 77%.

Figure 6

A 65-year-old female with right adrenal pheochromocytoma. MRI revealed a 5 cm solid lesion characterized by intermediate T2 signal (a,b) and no T1 signal drop in T1 out-of-phase sequences (c,d). Post-contrast acquisitions in arterial and portal venous phase (e,f) reveal inhomogeneous signal intensity and necrotic components.

Figure 7

A 67-year-old female with metastatic lung cancer. Axial arterial (a), portal (b), and delayed phase (c) showing large, inhomogeneous, left solid 4 cm adrenal lesion with irregular margins and foci of low attenuation, in keeping with partial necrotic phenomena. No infiltration of surrounding structure is seen. The lesion was referred to as adrenal metastasis.

Figure 8

A 67-year-old man with lung cancer. MRI shows a 7 cm nodular lesion on the left adrenal gland characterized by intermediate signal intensity on axial T2-weighted images (a) and perilesional edema (b). The lesion shows intermediate T1-intensity (c) with no signal loss in out-of-phase sequences (d), due to the absence of intralesional fat. DWI (e) and ADC map (f) demonstrated hypercellularity.