Pathways of Metastasis

Lymphatic System Very extensive drainage system that returns water and proteins from various tissues back to the bloodstream

Lymph System ©http://www. medem

Lymphatic vessels are even flimsier than capillaries Cancer just has to “push” the door in—does not require dissolving enzymes

Blood vessels Cancer cells have access to the bloodstream just as healthy cells do allowing them to enter the bodies' general bloodstream Once in the bloodstream, the cancer cells now have access to every portion of the body

Circulatory System ©http://library. thinkquest

Bloodstream is not as effective as the lymph system as it is flowing with greater pressure

Spreading of the cancer cells through surgery (uncommon)

Fertile soil theory of metastasis In 1889, Stephen Paget proposed that cancer cells shed from an initial tumor were dispersed randomly throughout the body by the circulatory system

He called these circulating cancer cells "seeds" and proposed that only some seeds fall onto fertile soil--organs where they can grow they encounter and then grow in the surrounding organ

About 30 years later, a researcher named James Ewing countered Paget's theory by arguing that cancer cells don't spread randomly throughout circulation in search of fertile soil

He suggested that cancer cells become trapped in the first small blood vessels they encounter and then grow in the surrounding organ

Physicians today still use the term “seeding” to explain which organs the cancer cells have spread