Anatomic basis for lymph node counts as measure of lymph node dissection extent: a cadaveric study

Objective: To determine the number, variability, and distribution of pelvic lymph nodes to better understand the utility of the node count as a surrogate for the dissection extent. Although pelvic lymph node dissection (PLND) at radical cystectomy for bladder cancer is critical for disease control and staging, debate regarding the measurement of dissection adequacy remains. Many have proposed minimum node counts, yet an anatomic study assessing the number and variability of lymph nodes in the PLND templates is lacking.

Materials and methods: Super-extended PLND was performed on 26 human cadavers, and the lymph nodes within each of 12 dissection zones were enumerated by a single pathologist. We calculated the mean, standard deviation, and range of nodal yield within each dissection region. The super-extended and standard dissection templates were compared using the paired t test.

Results: Super-extended PLND yielded a mean of 28.5 ± 11.5 lymph nodes, with a total node count range of 10-53 nodes. In contrast, the nodal yield within the standard template was 18.3 ± 6.3 nodes, with a range of 8-28 nodes (P <.001). No significant differences were seen in lymph node counts when stratified by age, sex, or cause of death.

Conclusion: Using a cadaveric model and a single pathologist to eliminate many of the factors affecting the nodal yield in surgical series, we found substantial interindividual differences, with counts ranging from 10 to 53 nodes. These results have demonstrated the limited utility of lymph node count as a surrogate for the dissection extent and illustrated the challenges associated with implementing a surgical standard for minimum lymph node counts.