Intranodal Mapping Using Carbon Dye Results in More Accurate Lymph Node Staging in Colon Cancer Patients

Introduction: Small nodal tumor infiltrates (SNTI)-defined as isolated tumor cells and micrometastases-are associated with worse disease-free and overall survival in stage I and II colon cancer patients. Their detection, however, remains challenging. The objective of the present study was to evaluate whether there is a correlation between the location of SNTI and phagocytosed carbon dye particles in sentinel lymph nodes (SLN) of colon cancer patients.

Materials And Methods: Isosulfan blue and carbon dye were injected intraoperatively near the tumor to mark the SLN. Serial sections of SLN were stained with hematoxylin-eosin and immunohistochemistry. Intranodal distribution of phagocytosed carbon particles was compared to the presence of SNTI.

Results: Of a cohort of 159 patients, 24 patients had SNTI in their lymph nodes (LN). SNTI were found in a total of 116 LN of which 66 were SLN and 50 were non-SLN. In 59, these 116 LN with SNTI phagocytosed carbon dye were found (50.9 %). Phagocytosed carbon dye was identified significantly more often in SLN (49 of 66 SNTI positive SLN) compared to 10 of 50 SNTI positive non-SLN (p < 0.001). In 52 out of 59 LN (88.1 %), phagocytosed carbon dye was in close proximity to SNTI.

Conclusions: In the majority of patients, SNTI are located in the same SLN compartment as phagocytosed carbon dye particles. Our investigation provides evidence that the use of carbon dye facilitates SNTI detection and improves LN staging in colon cancer. Therefore, the concept of intranodal mapping-which has been previously described for melanoma-can be extended to colon cancer patients.