The “peripheral wash-out sign” in hepatic malignant lesions

Excerpt

The “peripheral wash-out sign”, described by Mahfouz et al. [1], is a typical feature that can be seen on gadolinium-enhanced MR imaging in case of hepatic malignancy [1]. This sign refers to a malignant hepatic lesion with a rim of hypointensity (wash-out) relative to its center and surrounding parenchyma on delayed T1 weighted post-contrast sequences [1], in particular when a peripheral enhancement in arterial phase is present (Figs. 1, 2). This sign may be explained by the difference in vascularity between the peripheral portion (growing vascularized tissue) and the center of malignant lesions (poorly vascularized tissue); indeed, this latter becomes necrotic because the tumour outgrows its blood supply or because it has a fibrotic component [1]. In the study by Mahfouz et al., the “peripheral washout sign” showed a sensitivity of 24.5% and a specificity of 100% for the diagnosis of hepatic malignancy. Because of its high specificity the “peripheral washout sign” has been described as a typical finding of malignant hepatic lesions, in particular cholangiocarcinoma (Fig. 3) and metastasis, and absent in benign lesions.

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