There are no strict definition of what separates "childhood cancers" from cancers in young adults or when exactly a person no longer velons to young adults category. But as stats suggests that between the age of 20 and 39 are often thought as young adults.

Cancer is uncommon in young adults, but there is a wide variety of cancer types which can occur in this age group, and by treating these cancers it can be challenging.

Cancers can start in children or in teens which are less common. The types of cancer that develops in children and teens are usually different from the types that develop among adults. Childhood cancers are those which could possibly result from gene changes that take place at a very early phase in life and it sometimes can come even before birth. Unlike those cancers adults develop, children and teens are different from them as they are not strongly linked to lifestyle or environmental risk factors.

The most common cancers in young adults

Various kinds of cancers seen among young adults are not unique to this age group, but they are most common types at this age range which are different from those in children or older adults.

Some of the most common cancers in young adults are:

• Breast cancer

• Lymphomas (non-Hodgkin and Hodgkin)

• Melanoma

• Sarcomas (cancers of connective tissues like muscles and bones)

• Cancers of the female genital tract (cervix and ovary)

• Thyroid cancer

• Testicular cancer

• Colorectal cancer

• Brain and spinal cord tumors

Sources - American Cancer Society