There is a novel pattern of lymph node-mediated metastasis to distant organs. We call it lymph node-mediated hematogenous metastasis [1-3].

Tumor cells invade the blood vessels in the superficial layer of lymph nodes and spread to distant organs as circulating tumor cells in the blood.

Current anatomical textbooks do not describe the blood vessels in the superficial layers of lymph nodes.

Recently, studies have been reported that support this form of metastasis [4, 5].

【Video Description】
Tumor cells reach the marginal sinuses of the lymph nodes via the lymph vessels.
Tumor cells proliferate in the marginal sinuses and eventually invade the parenchyma. Tumor cells through the veins reach the bloodstream and circulate as tumor cells.

References
[1] L. Shao, K. Takeda, S. Kato, S. Mori, T. Kodama, Communication between lymphatic and venous systems in mice, Journal of immunological methods, 424 (2015) 100-105.
[2] K. Takeda, S. Mori, T. Kodama, Study of fluid dynamics reveals direct communications between lymphatic vessels and venous blood vessels at lymph nodes of mice, Journal of immunological methods, 445 (2017) 1-9.
[3] T. Kodama, S. Mori, M. Nose, Tumor cell invasion from the marginal sinus into extranodal veins during early-stage lymph node metastasis can be a starting point for hematogenous metastasis, Journal of Cancer Metastasis and Treatment, 4 (2018) 56.
[4] E.R. Pereira, D. Kedrin, G. Seano, O. Gautier, E.F.J. Meijer, D. Jones, S.M. Chin, S. Kitahara, E.M. Bouta, J. Chang, E. Beech, H.S. Jeong, M.C. Carroll, A.G. Taghian, T.P. Padera, Lymph node metastases can invade local blood vessels, exit the node, and colonize distant organs in mice, Science, 359 (2018) 1403-1407.
[5] M. Brown, F.P. Assen, A. Leithner, J. Abe, H. Schachner, G. Asfour, Z. Bago-Horvath, J.V. Stein, P. Uhrin, M. Sixt, D. Kerjaschki, Lymph node blood vessels provide exit routes for metastatic tumor cell dissemination in mice, Science, 359 (2018) 1408-1411.