Background: Ultrasonography (US) is widely used for pre-operative detection of liver tumors. However, US does not have high resolution and very small tumors, tumors located near the liver surface, or those in cirrhotic livers are often not detected. Case Report: A 47-year-old woman with a previous surgery for sigmoid colon cancer (T3N1bM0 Stage3b) showed a liver tumor on the surface of segment 2 by contrast-enhanced computed tomography (CT) and gadoliniumethoxybenzyldiethlenetriaminepen-taacetic acid (Gd-EOB-DTPA) magnetic resonance imaging (MRI). However, preoperative US could not identify a tumor lesion at the same site. The most likely preoperative diagnosis was metastasis from her sigmoid colon cancer and laparoscopic liver resection was performed. Intraoperative ultrasonography (IOUS) did not identify the tumor, but it was visualized with indocyanine green (ICG) fluorescence at the surface of segment 2. Laparoscopic liver resection was performed under fluorescence guidance. Pathological examination showed a pseudotumor with negative margins.

Conclusion: ICG fluorescence imaging can allow visualization of liver tumors that are undetectable on Ultrasonography.

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