A better understanding of lymphatic drainage of the prostate with modern imaging and surgical techniques.

PURPOSE: In prostate cancer, the spread of cancer to the lymph nodes is often determined by sampling lymph nodes from the obturator region. Historical findings from this area are often used as the basis for calculating the risk of lymph node metastasis in patients with prostate cancer. Therefore, it is of utmost importance to determine whether this sampling is a realistic representation of actual risk of lymphatic spread. This is important for risk assessment as well as for targeting lymphatics in treatment.

MATERIALS AND METHODS: We attempted to reconcile historical anatomic descriptions with contemporary imaging and surgical experience to try to obtain an accurate description of the lymphatic drainage of the prostate.

RESULTS AND CONCLUSIONS: Although obturator lymph nodes are clearly one of the possible sites of spread of prostate cancer, their sampling was never intended to be a definitive description of the routes of lymphatic cancer or the absolute incidence of lymph node metastasis. There are multiple other lymphatic areas at risk, with drainage primarily from the periprostatic area to the deep branches of the internal iliac lymphatics. The subsequent spread is to the perirectal and lower sacral vessel lymphatics, the proximal external iliac, the obturator, the upper sacral, common iliacs, and, ultimately, the para-aortic lymphatics. Describing the risk of lymphatic spread of prostate cancer based on obturator lymph node dissection alone is not totally accurate and probably underestimates the actual risk by 50% or more. A better understanding of the routes of drainage should make therapy that targets the lymphatics more effective.