Lymph node retrieval after colorectal cancer surgery: a comparative study of the efficacy between the conventional manual method and a new fat dissolution method

Purpose This study compared the efficacy of two different methods for lymph node (LN) searching after colorectal cancer surgery: the fat dissolution and the conventional manual method. Methods For the fat dissolution method, we used a commercially available solution of collagenase and lipase (FD group). The primary endpoint was the number of identified LNs in the FD group compared to an historical control (control group) after adjusting by propensity score matching. Results Using 37 matched patients from each group, we identified 20.6 ± 7.2 LNs using the fat dissolution method compared to 13.5 ± 5.9 using the conventional method ( t test, P < 0.01). Three patients in the FD group received an inappropriate LN examination in terms of number, while the number of the retrieved LNs was < 12 in 12 patients in the control group. The mean diameter of LNs without metastasis was 3.2 ± 1.9 mm in the FD group, and 40% of metastasis cases were found in LNs < 5 mm in diameter. A pathological examination confirmed that using the fat resolution method did not change the morphological or immunochemical staining findings. Conclusion We demonstrated that fat dissolution had a positive impact on the number of retrieved LNs after colorectal cancer surgery without disturbing the microscopic observation.