Paradoxical uptake of Gd-EOB-DTPA on the hepatobiliary phase in the evaluation of hepatic metastasis from breast cancer: Is the "target sign" a common finding?

Purpose: The purpose was to describe magnetic resonance imaging (MRI) findings of breast cancer liver metastasis using gadoxetic acid (Gd-EOB-DTPA) with an emphasis on the added value of the hepatobiliary phase (HBP). Material and methods: Nine patients with 13 liver metastases were included in the study after the medical records of 29 breast cancer patients who underwent Gd-EOB-DTPA-enhanced MRI between February 2008 and June 2010 were reviewed. The diagnoses of liver metastasis were established by percutaneous liver biopsy or surgery and on the basis of image findings. Two radiologists retrospectively evaluated signal intensity (SI) and sizes of metastases and patterns of enhancement in an HBP. The SI ratio was calculated as the SI of the central hyperintense portion in "target" lesions divided by the SI of nearby normal liver parenchyma on the HBP. We also measured apparent diffusion coefficient (ADC) values from Diffusion Weighted Image (DWI). Results: Liver metastases were all hypointense [n=13/13 (100%)] on T1-weighted imaging (WI), and many lesions had a "target" appearance with a central high SI and a peripheral low SI rim (47%) on T2WI. Dynamic study showed rim enhancement on the arterial phase (85%) and a "target" appearance, consisting of a central enhancing portion with peripheral washout or hypointense rim, on the HBP (62%). The mean SI ratio was 0.7. The mean ADC value of "target" appearing metastases was 1.25 (×10^-3 mm²/s; range 1.3-1.6) compared with a mean value of 0.8 (×10^-3 mm²/s; range 0.8-1.4) in homogeneous defect on the HBP. There was statistically significant difference (P<.05). Conclusion: Breast cancer liver metastases commonly demonstrated as a peripheral ring enhancement on arterial dominant phase and a target sign with a central round enhancing portion and a peripheral hypointense rim on the HBP.