The fine structure of neoplastic invasion: invasion of liver, skeletal muscle and lymphatic vessels by the Rd/3 tumour.

Neoplastic invasion as seen in the rat Rd/3 neoplasm has been studied electron microscopically in three sites: abdominal wall, footpad and liver. This neoplasm invades by peripheral cell division and active cell migration. Neoplastic cells protrude many fine processes and compress host cells. Neoplastic cells invade lymphatic vessels in a way similar to that in which white blood cells penetrate them - by the protrusion of fine cytoplasmic processes and passage, sometimes in clumps through open cell junctions. There is no ultrastructural evidence of secretory phenomena.