<?xml version='1.0' encoding='UTF-8'?><xml><records><record><source-app name="HighWire" version="7.x">Drupal-HighWire</source-app><ref-type name="Journal Article">17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">HOSOKAWA, AYUMU</style></author><author><style face="normal" font="default" size="100%">TAMURA, HOTAKA</style></author><author><style face="normal" font="default" size="100%">ICHIHARA, AKIKO</style></author><author><style face="normal" font="default" size="100%">IMAMURA, NAOYA</style></author><author><style face="normal" font="default" size="100%">KAI, KENGO</style></author><author><style face="normal" font="default" size="100%">FUKUSHIMA, TSUYOSHI</style></author><author><style face="normal" font="default" size="100%">NANASHIMA, ATSUSHI</style></author><author><style face="normal" font="default" size="100%">KOMOHARA, YOSHIHIRO</style></author></authors><secondary-authors></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">Pathological Complete Response to Liver Metastasis With Pembrolizumab in a Previously Treated Patient With Microsatellite Instability-high Colorectal Cancer</style></title><secondary-title><style face="normal" font="default" size="100%">Anticancer Research</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2024</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2024-09-01 00:00:00</style></date></pub-dates></dates><pages><style  face="normal" font="default" size="100%">4119-4125</style></pages><doi><style  face="normal" font="default" size="100%">10.21873/anticanres.17241</style></doi><volume><style face="normal" font="default" size="100%">44</style></volume><issue><style face="normal" font="default" size="100%">9</style></issue><abstract><style  face="normal" font="default" size="100%">Background/Aim: Immune checkpoint inhibitors are effective in treating microsatellite instability-high (MSI-H) metastatic colorectal cancer (CRC). Pathological complete response to immune checkpoint inhibitors for MSI-H metastatic CRC have been described in several reports. Liver metastasis is known to predict resistance to ani-programmed death 1 (PD-1)/PD-1 ligand 1 (PD-L1) therapy in several cancers, including CRC. Case Report: Herein, we report the case of a 23-year-old man with MSI-H colorectal liver metastasis who exhibited a pathological complete response to pembrolizumab following systemic chemotherapies. Pathological examination of the primary lesion revealed strong HLA-class I and HLA-DR expression in cancer cells. Elevated PD-L1 expression was observed in areas of increased CD8-postive T cell infiltration. Additional pathological study of regional lymph nodes showed increased PD-L1 and CD169 expression. Conclusion: A detailed pathological examination revealed PD-L1 expression not only in the primary CRC lesion but also in regional lymph nodes. Recent studies have highlighted the significance of regional lymph nodes in anti-cancer immune responses. Therefore, pathological studies using resected lymph nodes might be beneficial for predicting the response of anti-PD-1/PD-L1 therapy.</style></abstract></record></records></xml>