Aspects of lymphatic vessel configuration of the human male urinary bladder and adjacent organs: A histological basis for understanding the spread of cancer metastases

The spread of cancer cells via lymphatic vessels (LVs) is supposed to be an early event in the dissemination process of bladder cancer metastasis. However, the configuration of LVs in the human bladder has not been extensively examined microscopically. Therefore the distribution of LVs in the bladder was investigated. Using D2-40 immunohistochemistry labeling, LVs of bladders and adjacent organs obtained from 10 donated male cadavers, in which the bladders were not dilated post mortem. The bladder smooth muscle layer contained abundant dilated LVs, especially close to the center of the thickness of the bladder body wall. The LVs also made a delicate network in the mucosal tissue, although the density was lower than that in the smooth muscle layer. Independent from the artery and vein, LVs ran along and bundled the smooth muscles. Externally, LVs tended to run in parallel with longitudinal smooth muscles of the outer walls, especially at the posterior surface near the bladder neck. Additional LVs were traced in adjacent organs: prostate, seminal vesicles and rectum. The present study indicates that clinical interventions should be attentive with the treatment of bladder cancer patients, especially considering the bladder neck or trigone area, to prevent the spread of cancer cells via LVs. •The mucosal and submucosal lymphatic vessels of the urinary bladder make a rich delicate network: most parts were separated from the artery and vein.•In wall of the urinary bladder, the highest density of lymphatic vessels was seen in the most central zone of the smooth muscle layer wall of the organ.•Externally, lymphatic vessels tended to run in parallel with longitudinal smooth muscles of the outer wall, especially at the posterior surface, near the bladder neck.•The density of lymphatic vessels in the bladder smooth muscle was higher than that in the prostate, seminal vesicle, ureter and urethra. The density of lymphatic vessels in the smooth muscle of the bladder trigone was higher than that in the smooth muscle of the bladder dome.