Accurate diagnosis of metastatic lymph nodes (LNs) is essential in choosing appropriate treatment for gastrointestinal carcinoma. Our aim was to evaluate the diagnostic power of 5-aminolevulinic acid (5-ALA) for LN metastasis in mouse rectal cancer. Colorectal cancer cell lines, isolated cells from normal LNs, and orthotopic mouse model incorporating enhanced green fluorescent proteintagged and untagged human rectal cancer cells were studied after 5-ALA administration by using confocal microscopy, fluorescence stereomicroscopy, fluorescence lifetime imaging microscopy (FLIM), multichannel spectrophotometry and macroconfocal imaging system to precisely detect LN metastases. In vitro confocal microscopic analyses showed that all colorectal cancer cell lines tested were positive for 5-ALA-induced fluorescence, whereas isolated normal LN cells were negative. 5-ALA-induced protoporphyrin IX (PPIX) fluorescence, verified by FLIM and multichannel spectrophotometry, revealed LN metastases in mice-bearing human rectal cancer cells. Occult LN metastases, unrecognized on white-light imaging and simplified hematoxylin-eosin analyses, were readily detectable on 5-ALA-induced PPIX fluorescence imaging. In vivo macroconfocal images clearly revealed PPIX-fluorescence-positive cancer cells in draining lymph vessels and nodes. Together with specific speckled patterns of PPIX-fluorescence in metastatic lesions, the PPIX-fluorescence intensity ratio of metastatic and nonmetastatic lesions discriminated metastasis with 100% sensitivity and 100% specificity in excised whole LN samples. These results show that fluorescence diagnosis with 5-ALA is very accurate in the detection of LN micrometastases of mouse rectal cancer, suggesting that this feasible diagnostic approach is applicable to target sectioning of metastases of resected fresh whole node samples in pathology laboratories. ' UICCKey words: lymph node metastasis; rectal cancer; 5-aminolevulinic acid; fluorescence lifetime imaging microscopy; macroconfocal imaging Colorectal cancer is the second most frequent malignant tumor encountered in developed countries. 1,2 Lymph node (LN) metastasis is a common feature of metastasis associated with advanced colorectal cancer and serves as an important prognostic indicator for patients with colorectal cancer. 3,4 Accurate diagnosis of LN metastasis is essential for designing therapeutic strategies and assessing outcomes of patients.Computed tomography (CT) and magnetic resonance imaging are commonly used modalities capable of detecting LN metastasis of colorectal cancer. It is well known that the sensitivity of these methods in detecting metastatic nodes is up to about 67% 5-7 because the diagnostic criterion for LN metastasis by using these modalities is principally based on their size. Fluorodeoxyglucosepositron emission tomography (FDG-PET) is also an effective tool for detecting malignant disease, which takes advantage of the difference in glucose metabolism. 8,9 However, the diagnostic sensitivity of FDG-PET for metastatic LN from...

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Object An indocyanine green derivative (ICG-sulfo-OSu) was used as the labeling substance for monoclonal antibody, and a fluorescence imaging system appropriate for ICG-sulfo-OSu excitable by infrared rays (IR) was developed. The goal of this study was to demonstrate antibody labeling at the tissue level using this new imaging system. Materials and Methods ICG-sulfo-OSu labeled mouse anti-human carcinoembryonic antigen (CEA) monoclonal antibody, a newly developed imaging system, and an infrared ray microscope were employed in this experiment. Paraffin sections of humancolon cancer previously proven to have cross-reactivity to anti-CEA antibody were examined. Results Positive staining was seen as a brownish discoloration of oxidized 3,3'-diaminobenzidine tetrahydrochloride (DAB) in sections that reacted with ICG-sulfoOSu-labeled anti-CEA antibody, and the fluorescence was well-matched with the oxidized DABpositive sites. Conclusion Specific antibodies labeled with ICG-sulfo-OSu have significant affinity to cancer cells and seem to reflect sufficient amounts of fluorescence by IR to be useful in a system for the endoscopic detection of micro cancers using the immunohistochemical staining method. (Internal Medicine 38: 537-542, 1999)