Benign tumors are usually encapsulated and do not invade adjacent tissue

Cancerous/malignant tumor usually is not encapsulated and eventually invades surrounding tissue

Migration

Some viruses induce cancers i.e. viral gene expression
affects the normal cell cycle controls

 Aberrant chromosome number - High metabolic requirements

High incidence of cancers run in families – familial cancer

Mutations in genes that control cell growth and division

•travel through the vascular system and form distant tutors elsewhere
•production of matrix degrading enzymes which cleave the extracellular matrix
•making space for invasion and freeing growth and angiogenic factors trapped inside

second mutation occurs in one of the retinal cells at an early age, leading to disease

have already received one mutation from one of their parents

develop multiple tumors involving both eyes

must have two mutations