Presentation
Known to have colorectal cancer, underwent dynamic liver MRI for evaluation of metastatic disease.
Patient Data
Three typical metastases are visible in the segments 3, 2, and 6 of the liver.
Another smaller lesion with mild T2 hyperintensity and hypo-enhancement is seen anterior to the right lobe metastasis mimicking another metastatic lesion. This lesion has mild T1 hyperintensity and shows dropout on opposed phase images, and does not show diffusion restriction, favoring the diagnosis of focal fat infiltration.
A nodule with macroscopic fat signal in the right adrenal gland may represent a myelolipoma or lipoma. Another small nodule is present in the left adrenal gland. It shows signal drop on opposed phase images, findings compatible with an adenoma. The difference between macroscopic and intracellular microscopic fat is visible in the right adrenal nodule (lipoma or myelolipoma) and the left adrenal adenoma and focal hepatic fat deposition—the former drops on fat saturation sequences and the latter on opposed phase images.
Renal crossed fused ectopia is depicted as an incidental finding.
The white and yellow arrows depict the hepatic focal fat deposition and the right adrenal fat containing nodule.
Case Discussion
Focal fat infiltration usually has a geographic appearance and occurs in typical locations such as segment 4 or around the gallbladder bed. Occasionally the fat infiltration may be round and occur in unusual locations and mimic metastatic lesions in patients with known cancer. The absence of diffusion restriction and signal dropout on opposed phase images are the clue to the correct diagnosis.
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