Giant adrenal myelolipoma : A case report with USG, CT and MRI findings

Clinical History

A 50-year-old woman was admitted with complaint of abdominal discomfort and increased blood pressure. Ultrasound, CT and MRI were done and based on imaging findings a probable diagnosis of giant adrenal myelolipoma was made. Finally fine needle aspiration confirmed our diagnosis.

Imaging Findings

A 50-year-old woman was admitted with complaint of intermittent right flank pain and abdominal discomfort. Patient also showed increased blood pressure. There was no other significant history. Physical examination revealed a large palpable mass in the right abdomen. Laboratory evaluation of blood and urine were normal. Ultrasound showed large heterogenously echogenic mass in suprarenal location on right side. Computerised tomography showed a giant well defined retroperitoneal mass in right supra renal region. Lesion was heterogeneous with large hypodense areas showing CT value of fat and enhancing irregular foci of soft tissue component. Approximate size of the lesion was 16x12x13.2 cm (Fig. 1). Magnetic resonance imaging (MRI) showed well defined heterogeneous high signal intensity mass with interspersed areas of intermediate signal intensity on both T1- and T2-weighted images with suppression on fat saturated images (Fig. 2 ). No significant contrast enhancement was seen except for the enhancing foci of soft tissue elements within the mass. The mass displaced the liver anteriorly and right kidney posteroinferiorly without invading them, the right adrenal gland could not be identified separately. Fine needle aspiration was done which showed gross appearance of fat globules on the slide. Microscopic evaluation revealed mature adipocytes and myeloid components, this finally confirmed our diagnosis.

Discussion

Myelolipomas are uncommon benign adrenal or rarely extra adrenal masses consisting of adipose and haematopoietic elements. Few cases have been reported since it was first described by Gierke in 1905 [1]. Most of them are asymptomatic and are usually diagnosed as incidentolomas in persons being imaged for some other clinical indication or they are discovered on autopsy. In autopsy series, its prevalence is between 0.08% and 0.20%, with equal sex distribution [2]. It varies in size from microscopic foci to 8 cm in diameter. Giant adrenal myelolipoma is very rare clinical entity. Only rarely adrenal myelolipoma can grow large and can produce symptoms like abdominal pain and discomfort. Most patients are in their fourth to sixth decade. Myelolipomas that spontaneously haemorrhage are usually larger than 10 cm. No malignant potential is associated with these lesions. Its cause is unknown. Possible explanation of its pathogenesis includes retention of embryonic rests, extramedullary haematopoiesis, or bone marrow embolisation. The most widely believed theory is of metaplastic origin [3].The differential diagnosis includes renal angiomyolipoma, retroperitoneal lipoma or liposarcoma.
CT and ultrasonography are sensitive and valuable techniques in the imaging and diagnosis of these fatty tumours of the adrenal gland. Although MRI does not add significantly to the tissue characterisation, it may assist in confirming the adrenal origin of these tumors [4]. Ultrasound features of myelolipoma are that of an echogenic mass with few hypoechoic areas in the predominantly myeloid components. Hyperechoic areas with acoustic shadowing are associated with calcification. The margins of the lesion are often difficult to define due to a lack of contrast with the surrounding retroperitoneal fat [5]. Myelolipomas have characteristic CT appearances. Presence of gross fat is diagnostic. Other features include presence of varying amounts of enhancing solid elements, pseudo capsule and punctate calcifications [4]. On MRI predominantly fatty areas in myelolipoma usually have increased signal intensity on T1-weighted MR images. On T2-weighted images, the appearance is complicated by the presence of admixed marrow like elements, which have intermediate signal intensity. Fat-suppressed techniques may be the best method for demonstrating the fat in a myelolipoma with MR imaging. The presence of marrow like elements or haemorrhage results in persistent areas of increased signal intensity on fat-suppressed MR images [5]. Although it is possible, adrenal myelolipoma do not frequently demonstrate signal dropout on opposed-phase chemical shift imaging because of insufficient water content.
When myeloid material, calcification or haemorrhage is too extensive, the fat content may not be recognised. Such a tumour may be indistinguishable from other adrenal neoplasm. Also when large, myelolipomas can be confused with other entities such as a retroperitoneal liposarcoma. In this case, fine-needle aspiration is indicated as a procedure with little associated morbidity [3]. Surgical excision is reserved for myelolipomas with mass effect or bleeding.

Differential Diagnosis List

Final Diagnosis

Giant Adrenal Myelolipoma

URL:	https://www.eurorad.org/case/8737
DOI:	10.1594/EURORAD/CASE.8737
ISSN:	1563-4086