Proposal for novel histological findings of colorectal liver metastases with preoperative chemotherapy

This study aimed to clarify the histological characteristics related to preoperative chemotherapy for colorectal liver metastases (CRLM). Sixty‐three patients with CRLM were divided into two groups: CRLM with chemotherapy (41 cases, group A) and CRLM without chemotherapy (22 cases; surgical treatment alone, group S) to identify the histological differences associated with chemotherapy. In addition, we investigated the effects of combination chemotherapy on the histology of metastatic lesions. Infarct‐like necrosis (ILN), three‐zonal changes, and cholesterol clefts were more frequent in group A than in group S (P < 0.05). ILN and three‐zonal changes were more common in the 5‐FU with leucovorin and oxaliplatin (FOLFOX), or 5‐FU with leucovorin and irinotecan (FOLFIRI) with or without additional bevacizumab groups than in group S (P < 0.05). Cholesterol clefts in the FOLFOX or FOLFIRI with bevacizumab group and foamy macrophages in the FOLFOX or FOLFIRI group were more common than in group S (P < 0.05). Cases with more than three of the four histological findings—i.e. ILN, three‐zonal changes, cholesterol clefts, and foamy macrophages—were more frequent in the FOLFOX or FOLFIRI with or without additional bevacizumab groups than in group S (P < 0.05). We showed histological findings for every representative chemotherapy regimen for CRLM to clarify the effects of preoperative chemotherapy.