Multifocal hepatic steatosis presenting as metatases

Clinical History

A male patient presenting with abnormal liver biochemistry had ultrasound and CT imaging demonstrating multiple liver lesions suggestive of metastases. He underwent a targeted biopsy which showed marked hepatic steatosis but no evidence of malignancy. Repeat biopsy and MRI confirmed the diagnosis of multifocal hepatic steatosis.

Imaging Findings

A 58-year-old clinically well male patient was referred by a gastroenterologist for investigation of abnormal liver biochemistry ( isolated elevated GGT of 80 : normal < 60). Liver ultrasound demonstrated multiple hyperechoic liver lesions with appearances suspicious for multiple metastases (Figure 1). He proceeded to CT thorax, abdomen and pelvis post oral and IV contrast which demonstrated multiple low attenuation lesions on portal venous phase with no evidence of chronic liver disease or a primary neoplasm. (Figure 2a and b). Triphasic protocol was not performed however. He proceeded to ultrasound guided focused 15 G core biopsy of a selected liver lesion. Histology demonstrated hepatic steatosis but otherwise normal liver parenchyma with no evidence of malignancy. This was presumed to be a sampling error and the patient underwent repeat targeted biopsy. Multiple 16 gauge core samples were obtained- once again histological analysis demonstrated no evidence of malignancy. The possible diagnosis of multifocal hepatic steatosis was then considered and the patient underwent MRI of liver with T2, T1 fat suppressed and T1 in and out of phase imaging. The lesions were iso or slightly hyperintense on T1 in phase imaging (Figure 3), and demonstrated signal drop off with sharp peripheral demarcation on T1 out of phase imaging (Figure 4). The lesions were isointense on T1 fat suppressed imaging (Figure 5). Findings were consistent with the diagnosis of multifocal hepatic steatosis. The patient was discharged and followed up in an outpatient setting and has remained clinically well.

Discussion

Hepatic steatosis is a well recognised and relatively common finding in imaging of the liver in its diffuse and focal forms. The more usual focal forms can be diagnosed with confidence on ultrasound when occurring as geographic lesions in the typical locations adjacent to the falciform ligament, in the gall bladder fossa and porta hepatis (1). Rarely CT or MRI is required to confirm the diagnosis. However there has been an increasingly described phenomenon of multifocal hepatic steatosis which has atypical imaging features easily confused with metastatic disease. The lesions typically appear as multiple focal lesions not occurring in a specific location which are hyperechoic on ultrasound and low attenuation on CT imaging. There have been a number of cases in the literature where the patient has had presumed metastatic disease on the basis of imaging and subsequently undergone intensive investigation and multiple biopsies in the search for a primary lesion (2). The diagnosis can be definitively made on MRI using either spectral fat suppression techniques or chemical shift imaging (as in our case). The lesions will appear as iso or slightly hyperintense on T1 "in phase" imaging, slightly hyperintense on T2 weighted imaging and suppress with T2 fat suppressed imaging (3). T1 weighted "out of phase" imaging (chemical shift) is particularly useful and will demonstrate marked peripheral signal drop off resulting in sharp demarcation of the lesions (3) (Figure 4). There is no enhancement following administration of contrast. The diagnosis of multifocal hepatic steatosis should always be considered in a patient presenting with multiple hepatic lesions, particularly if the patient is clinically well. Early use of MR imaging can prevent unnecessary investigation and the risk of multiple biopsies.

Differential Diagnosis List

Final Diagnosis

Multifocal hepatic steatosis

URL:	https://www.eurorad.org/case/6526
DOI:	10.1594/EURORAD/CASE.6526
ISSN:	1563-4086