The most dangerous feature of breast cancer is its ability to spread elsewhere in the body. Usually, the first sign of metastasis is that cancer cells are also found in the lymph nodes draining the tumor area. The first lymph nodes that cancer cells can reach via the lymphatic vessels are located in the armpit.

Researchers at the University of Turku in Finland analyzed the cancer-originated changes in the lymphatic vessels. They found that significant molecular changes take place in the lymphatics when cancer spreads into the lymph nodes. Those changes support cancer cells traveling into the lymph nodes and further metastasis of the cancer elsewhere in the body.