Detailed cadaveric analysis of perivesical lymph nodes in cystectomy specimens.

Perivesical lymph nodes were added to the 8th edition of American Joint Committee on Cancer (AJCC) staging for bladder cancer. Currently, these nodes are inconsistently evaluated at the time of radical cystectomy. The objective of this study was to provide a detailed anatomic evaluation of perivesical lymph nodes. A radical cystectomy was performed on six un-embalmed cadavers with wide resection of perivesical tissue and meticulous care to separate the pelvic sidewall lymph nodes (e.g. obturator, external iliac) from the bladder and perivesical en-bloc specimen. Perivesical tissue dissection in 2 mm slices was performed with a board-certified pathologist. Lymph node size and location were recorded. Gross tissue resembling lymph nodes were identified in the perivesical tissue in 50% (3/6) of the specimens, with a total of six grossly identified lymph nodes. The mean size was 7.5 mm (2-16 mm). On histologic analysis, 4 of 6 (66%) putative gross lymph nodes had confirmed lymphoid tissue. The mean distance of the lymph nodes from bladder wall was 9 mm (3-15 mm). Eight anatomic locations for perivesical nodes were developed: urachal, anterior bladder wall, posterior peritoneum, bladder neck, bilateral pedicle, bilateral lateral bladder wall. This cadaveric study with meticulous dissection of the perivesical space confirms that perivesical lymph nodes are a distinct entity and separate from other lymph nodes in the true pelvis. Perivesical lymph nodes are not present in all subjects and pathologic evaluation is more difficult owing to the surrounding fat. We herein propose perivesical regions for evaluation which can serve as a foundation for future studies and anatomic grossing techniques.