Some young people believe toilet seats can give you cancer and only fat people get the disease, a poll has found.
Other myths include being able to catch cancer from kissing, a kick in the genitals causing the disease and eating coloured jelly sweets increasing the risk.
Living near electricity pylons and keeping a mobile phone in your bra are also exposed in the list of common beliefs.
The poll of 13 to 24-year-olds for the Teenage Cancer Trust comes as data shows the rate at which children are dying from cancer has fallen almost 60% over the last 40 years.
In the late 1960s, around 940 children died from the disease every year but this has dropped to around 290 a year, according to the report.
The latest survey of 520 young people revealed the top myth as being everyone is born with the cancer gene (believed by 53%).
Some 37% believe people are never really cured of cancer, 36% think mobile phones cause brain tumours while 35% are worried about electricity pylons.
More than one in 10 (15%) young people believe keeping a mobile phone in your bra causes cancer, and 12% think a kick in the genitals causes testicular cancer.
More than one in five (22%) think the colour of your skin determines your cancer risk, 19% think cancer in pregnancy is passed on to the baby, 7% believe only fat people get cancer, 8% are worried about eating coloured jellies and 6% believe cancer can be caught from kissing.
Simon Davies, chief executive of Teenage Cancer Trust, said: "Cancer is a complex and frightening disease so it is easy to understand why such strange myths exist."