The effect of colonoscopic tattooing on lymph node retrieval and sentinel lymph node mapping.

Background: In colorectal cancer (CRC), colonoscopic tattooing is performed to mark the tumor site before laparoscopic surgery.

Objective: To determine whether colonoscopic tattooing can be used to refine staging accuracy by increasing the lymph node (LN) yield per specimen and to determine its accuracy as a sentinel LN procedure.

Design: Retrospective, case-control study. All LNs were microscopically examined for the presence of carbon particles.

Setting: A university hospital and a teaching hospital.

Patients: A consecutive series of 95 tattooed patients who had surgery for CRC between 2005 and 2009. A series of 210 non-tattooed patients who had surgery in the same time period served as controls.

Main Outcome Measurements: Total number of LNs retrieved, detection rate, and sensitivity of tattooing as a sentinel node procedure.

Results: A higher LN yield was observed in patients with preoperative tattooing, median (interquartile range) 15 (10-20) versus 12 (9-16), (P = .014). In multivariable analysis, the presence of carbon-containing LNs was an independent predictive factor for a higher LN yield (P = .002). The detection rate was 71%, with a median of 5 carbon-containing LNs per specimen. If preoperative tattooing was used for sentinel node mapping, the overall accuracy of predicting LN status was 94%. In the 24 N1 cases, there were 4 false-negative procedures (sensitivity 83%).

Limitations: Retrospective series.

Conclusion: After tattooing of CRC, the LN yield was higher than in a control group, and it could be used as a sentinel node procedure with acceptable accuracy rates. Because LN yield and sentinel node mapping are associated with improved diagnostic accuracy of LN involvement, preoperative tattooing can refine staging.