Delineating precise surgical resection areas: recent advances in NIR-II fluorescence imaging molecular probes.

Precise delineation of surgical resection margins is a pivotal determinant of oncologic surgery outcomes, with R0 resection serving as the gold standard for maximizing local control and long-term survival. However, intraoperative identification of tumor boundaries remains challenging. Conventional tools such as frozen section pathology offer limited field coverage, are labor-intensive, time-consuming, and may yield sampling errors, particularly in anatomically complex or highly infiltrative lesions. Near-infrared II (NIR-II, 1000-1700 nm) fluorescence imaging has emerged as a transformative modality for real-time intraoperative navigation. Leveraging reduced photon scattering, minimal tissue autofluorescence, and deeper penetration compared with NIR-I and other optical approaches, NIR-II imaging enables high-contrast visualization of tumor margins while preserving adjacent normal structures. Over the past decade, the molecular probe landscape for NIR-II imaging has rapidly evolved-from early non-specific small molecules and inorganic nanomaterials to the latest generation of targeted agents designed to bind tumor-specific biomarkers. These advances have facilitated more accurate tumor-normal tissue contrast in a range of surgical contexts, including glioma, hepatobiliary malignancies, colorectal cancer, and head-neck tumors. Several first-in-human and ongoing clinical trials have demonstrated the feasibility, safety, and intraoperative utility of NIR-II molecular probes. Nevertheless, issues related to regulatory approval, probe pharmacokinetics, real-time quantitative imaging, and integration with multimodal surgical systems remain to be addressed. This review summarizes current concepts of precise surgical resection margins, outlines the origin and principles of NIR-II fluorescence imaging, and provides an in-depth discussion of targeted molecular probe development, preclinical and clinical progress, and their role in tumor margin delineation. Finally, we highlight existing limitations and future opportunities for translating NIR-II probes into routine surgical oncology practice.