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.