Teaching Case

Patient underwent an ultrasound examination of the abdomen and pelvis to follow-up some uterine leiomyomas. Her history and laboratory tests were otherwise unremarkable.

A 37 year-old female underwent an ultrasound examination of the abdomen and pelvis to follow-up some uterine leiomyomas. Her history and laboratory tests were otherwise unremarkable. At sonography, a large echoic mass was seen in the right upper quadrant originating from the ipsilateral adrenal. Despite its large diameter, the lesion was clearly demarcated from the liver and right kidney. At US, the mass had a heterogenously hyperechoic appearance. Such a finding, in association with the occurrence of a beam propagation artifact, suggested the presence of fat tissue within the bulk. A dual-phase contrast-enhanced CT examination was performed in another centre. A portion of the abdominal mass showed adipose density, another portion, localized medially, was almost isodense to muscle and displayed inhomogenous contrast uptake; a third portion displayed intermediate density. A MR scan was obtained afterwards in order to further characterize the right-sided adrenal. Axial GRE T1w sequences with in-phase, out-of-phase TEs (chemical shift imaging) and with fat suppression were performed. tSE T2w images of the whole abdomen were also obtained. Tiny peripheral foci of hyperintense signal on T1w images that nulled on fat-suppressed T1w scans (macrovescicular, mature fat), large areas of mildly hyperintense signal on in-phase T1w images that nulled on out-of-phase T1w scans (microvescicular intracytoplasmic fat) and relatively hypointense portions on all sequences (solid, non-adipose tissue) were simultaneously present in the right adrenal.

With reference to the history of the patient, a non-hyperfunctioning adrenal mass must be considered. In this field, differentials may consist either of malignant lesions such as metastases or primary adrenal carcinomas or benign lesions. Both the clinical setting of young age with no known primary tumor and the imaging findings (mature fat) allow to rule out the hypothesis of malignancy. Adenomas and myelolipomas are the candidates amongst benign lesions. Although adenomas are much more common than myelolipomas, the right-sided adrenal mass in our patient contained not only microvescicular intracytoplasmic fat, but a mixture of pure fat and contrast-enhancing non-adipose tissue as well, making the latter hypothesis much more likely. Nevertheless, a collision tumor originating from an adenoma and a lipoma could not be ruled out with absolute accuracy on the basis of imaging only. Due to its size and possible future bleeding the mass was surgically excised.