Indocyanine green fluorescent imaging for detecting extrahepatic metastasis of hepatocellular carcinoma

Indocyanine green (ICG) fluorescent imaging has been used effectively to identify hepatocellular carcinoma (HCC) in intraoperative setting. However, whether extrahepatic metastatic lesions from HCC can also be detected by this imaging is unknown. This study was conducted on 17 patients with suspected extrahepatic HCC metastases in the lung (n = 3), adrenal gland (n = 1), lymph node (n = 7), peritoneum (n = 5) and both lymph node and peritoneum (n = 1). ICG was administered intravenously at a dose of 0.5 mg/kg prior to operation for liver function evaluation. Intraoperative ICG fluorescent imaging was performed with a near-infrared light camera system. The surgical specimens were also examined in all cases for the presence of ICG fluorescence. Of 28 lesions for which ICG fluorescence was examined intraoperatively, 24 lesions exhibited fluorescence and were proved to be HCC metastases pathologically. Five of them were newly identified by ICG fluorescent imaging. The other four lesions included two HCC metastases and two benign tumors. Of 33 suspicious metastatic lesions extirpated, 26 lesions emitting fluorescence from the specimen were all metastatic HCC. The other 7 lesions consisted of 6 benign tumors and one HCC metastasis. Accordingly, the positive predictive value of in vivo and ex vivo ICG fluorescent imaging were both 100 %, while the negative predictive value of those methods were 50 and 86 %, respectively. Extrahepatic metastases from HCC exhibited ICG fluorescence when illuminated by near-infrared light, indicating their capability to transport ICG. This imaging can be a useful tool for intraoperative detection of metastasis in HCC patients.