Giant right adrenal myelolipoma

Clinical History

A 65-year-old man presented with recent right abdominal pain and anorexia. He was apyretic and had a one-year history of fullness, heartburn and abdominal distension. Inflammatory parameters were increased and physical examination revealed abdominal distention and right abdominal pain and dullness.
Abdominal ultrasound and contrast-enhanced CT (computed tomography) were performed.

Imaging Findings

Abdominal ultrasound showed features suggestive of acute cholecystitis. It also demonstrated an incidental finding of a heterogeneous and well-defined mass, with echogenicity suggestive of fat and a larger sectioned axis of 16.5x12.5 cm, causing inferior displacement of the right kidney (Fig. 1).

Contrast-enhanced CT was done to clarify ultrasound findings. It showed a 16x17x12 cm heterogeneous lesion, with predominantly adipose density and some central punctiform calcified foci (Fig. 2b and e). It was localised in the retroperitoneum, between the right lobe of the liver and the right kidney, and caused kidney’s inferior displacement, as well as inferior vena cava’s medial deviation and right colon’s anterior deviation (Fig. 2). There were no tissue planes with the right adrenal gland.

Discussion

Adrenal myelolipoma is a rare and benign tumour, composed of adipose tissue and haematopoietic elements [1, 2]. 3-4% of primary adrenal masses are myelolipomas [3]. It's more common in females, between fifth and seventh decades of life and affects the right gland more frequently [1, 3]. Its size is variable, normally between 2 and 10 cm. Larger tumours are rare [1].

The aetiology remains unclear, although it's believed that metaplasia of adrenocortical cells induced by infection, necrosis or stress, is the trigger that induces tumoural growth [2, 3].

The majority of adrenal myelolipomas are non-functioning [3]. However, 10% are associated with endocrine dysfunction, such as Cushing’s syndrome, Conn’s syndrome and congenital adrenal hyperplasia [1, 2].

Patients are usually asymptomatic [2]. Nevertheless, abdominal pain, discomfort or an acute abdomen may be seen [2]. The most significant complication, however uncommon, is acute haemorrhage, which is more frequent in larger tumours [1, 2]. High intra-capsular pressure, caused by rapid tumour growth, can lead to capsular rupture and haemorrhage [4].

In 90% of cases, the diagnosis can be confidently established on CT or MRI (Magnetic Resonance Imaging) [2]. However, when there is uncertainty, percutaneous biopsy is important [5].

Myelolipoma’s ultrasonographic appearance varies with its tissue components [5]. It shows a solid and heterogeneous mass, that is more hyperechoic if fat tissue is predominant, or more hypoechoic if marrow tissue is abundant [2, 5].

On CT, the typical image reveals an adrenal, encapsulated and well-circumscribed mass, with high content of adipose tissue interspersed with higher-attenuation myeloid tissue, with global attenuation values between -20 and -30 Hounsfield Units (HU) [5]. Intra/peritumoural haemorrhage appears as areas of increased density (subacute phase) [2, 6]. Calcifications may occur in 20% of cases and post-contrast CT shows myeloid tissue enhancement [2, 6].

MRI demonstrates hyperintense signal due to fat tissue on T1-weighed images, which is decreased by fat-suppression techniques. It has intermediate signal intensity on T2-weighed images, consistent with fat and marrow tissue mix [2, 5].

At angiography, myelolipoma is predominantly avascular [2].

Myelolipomas are usually treated conservatively when less than 4 cm because they're frequently asymptomatic and rarely bleed spontaneously [3, 7]. Imaging follow-up is recommended [7].
Surgery is reserved for functional, symptomatic, growing or larger myelolipomas (more than 4cm) [3]. Prognosis is very good [2].

On CT, our patient presented with a giant lesion suggestive of myelolipoma; however we could not exclude liposarcoma, which is also a fat-containing mass that can present with calcifications. Because of its size and the presence of symptoms, surgical treatment was chosen.

Histopathological examination confirmed myelolipoma.

Written informed patient consent for publication has been obtained.

Differential Diagnosis List

Final Diagnosis

Right adrenal myelolipoma

URL:	https://eurorad.org/case/15851
DOI:	10.1594/EURORAD/CASE.15851
ISSN:	1563-4086