Relationship Between Histopathological Growth Patterns and Indocyanine Green Fluorescence in Colorectal Liver Metastases.

BACKGROUND/AIM: In colorectal liver metastases (CRLM), peritumoral indocyanine green (ICG) fluorescence has traditionally been attributed to cholestasis caused by compression of the surrounding liver parenchyma; however, the mechanisms underlying ICG retention remain incompletely understood. Histopathological growth patterns (HGPs) represent distinct modes of tumor-liver interaction and may therefore influence ICG fluorescence characteristics. This study aimed to investigate the relationship between ICG fluorescence patterns and HGPs in CRLM.

PATIENTS AND

METHODS

This retrospective study included 46 patients who underwent hepatectomy for CRLM at our institution between January 2020 and December 2024. ICG was administered intravenously 2-14 days before surgery. Histopathological specimens were examined using fluorescence microscopy to evaluate the presence or absence of ICG fluorescence and fluorescence patterns. HGPs were classified into desmoplastic, pushing, and replacement types according to international consensus guidelines.

RESULTS

All fluorescent lesions exhibited a rim-fluorescence pattern. ICG fluorescence was detected in all desmoplastic-(22/22) and pushing-type (2/2) metastases and in most replacement-type metastases (20/22), with no significant differences in fluorescence detection rates or fluorescent rim width among HGPs. Notably, non-fluorescent lesions were observed exclusively in replacement-type metastases, including a case following short-interval preoperative ICG administration.

CONCLUSION

Although ICG fluorescence characteristics were not directly associated with histopathological growth patterns, the presence and absence of fluorescence in replacement-type metastases suggest that ICG fluorescence imaging reflects functional tumor-liver interactions beyond mechanical compression alone.