Transillumination improves lymph node yield in left-sided colorectal cancer: an ambispective cohort study

Accurate lymph node (LN) staging is essential for prognosis and treatment decisions in colorectal cancer (CRC). Existing methods to assist LN retrieval, such as fat-clearing and methylene blue staining, improve yield but are complex, time-consuming, and require additional reagents. This study aimed to develop and evaluate a novel transillumination device that exploits adipose tissue transparency to facilitate LN retrieval. The study comprised two phases. Phase one involved the development and feasibility evaluation of the transillumination device. In phase two, 125 left-sided CRC specimens were prospectively processed using the device (Transillumination Group, TG), and 255 retrospectively collected cases processed by conventional palpation served as the Control Group (CG). LN yield, sampling time, and mis-retrieved non-lymphatic tissues were compared. For the device development, blue transillumination markedly enhanced visual contrast between LNs and surrounding tissue. LN yield was higher in TG than CG (21.82 ± 6.01 vs. 13.67 ± 3.64; adjusted IRR, 1.57; 95% CI, 1.48–1.66; P < 0.001), and the percentage of LNs ≤ 2 mm retrieved in the TG was significantly higher than that in the CG (21% vs. 10.5%, P < 0.001). Sampling efficiency improved (1.41 ± 0.69 vs. 2.04 ± 1.45 min/LN; P < 0.001), and fewer mis-retrieved tissues were observed in TG (0.53 ± 0.72 vs. 1.32 ± 1.10; IRR, 0.40; 95% CI, 0.31–0.52; P < 0.001). The transillumination device increases LN yield and sampling efficiency while reducing mis-retrieved tissues, without the need for chemical reagents. It is a cost-effective, easy-to-implement tool in clinical practice, particularly advantageous for detecting small LNs.