Lymph Vessels of the Prostate
The lymph vessels of the prostate (Figure 32: k) drain to the medial iliac, hypogastric, and lateral sacral lymph nodes. They form a coarse network on the surface of the prostate, from which 3 to 5 lymph vessels emerge on each side: these run either in the lateral ligament of the urinary bladder, or under the peritoneum attached to the lateral pelvic wall, continuing to form coarse networks by dividing and merging, to drain to the medial iliac lymph node (Figure 32: 1) and the hypogastric lymph nodes (Figure 32: 3). If a lateral sacral lymph node (Figures 32: 5) is present, one of these lymph vessels will usually also enter this lymph node.
Some of the lymph vessels of the pelvic part of the urethra may be filled from the prostate, but these lymph vessels usually then drain to the same lymph nodes as mentioned above. Lymph vessels of the neck of the urinary bladder may also be filled from the prostate, but I cannot be sure if this involves communications between the prostate and urinary bladder lymph vessels. Gerota (Archiv für Anatomie und Physiologie, Volume 5/6, 1897) assumes that this is the case, as he has stated: “In man, the lymph vessels of the fundus of the bladder communicate with those of the prostate and seminal vesicles”. Walker  describes the lymph vessels of the prostate of the dog in detail, though it is difficult to determine which lymph nodes are involved from his description. According to his illustrations, lymph vessels of the prostate also drain into the deep inguinal lymph node and to lymph nodes located on the rectum, but I have not observed drainage from the prostate to either of these groups of lymph nodes.