Pathological Complete Response to Liver Metastasis With Pembrolizumab in a Previously Treated Patient With Microsatellite Instability-high Colorectal Cancer.

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.