Kids and Adults: What's the Difference?

The difference between childhood and adult cancers rarely comes down to simply age. Most tumors in children differ biologically from their adult counterparts and are typically due to the type of cell from which the cancer originates.

In the weeks after fertilization, the embryo develops into layers: ectoderm, mesoderm and endoderm. These layers lay the foundation for the development and maturation of tissues and organs in the body.

Adult cancers, such as lung, breast and colorectal, typically develop from epithelial tissue (adenocarcinomas), which come from the ectoderm or endoderm. Epithelial cells make up the skin and lining of the internal organs and glands. Alternatively, childhood cancers, including sarcomas (cancers of the bone or muscle) and leukemias (blood cancers), develop from the mesoderm.

Many childhood cancers form from primitive cells or embryonic cells found in developing fetuses and often manifest deep in the body. These cancers develop either because of genetics or an event in early fetal development, whereas adult cancers typically result from an accumulation of mutations caused by external sources, such as smoking or sun overexposure.

Researchers believe biological differences may point to why childhood cancers are more responsive to chemotherapy, which is designed to target rapidly dividing cells.

Epithelial cells are normally resilient because they are exposed to environmental influences, making them more resistant to treatment if they become cancerous. Vulnerable childhood cancer cells, however, are ideal targets for chemotherapy. Indeed, childhood cancer survivors are less likely to have a recurrence than adults, and the five-year survival rate for all childhood cancers is higher (80 percent compared with 66 percent).

[Assessing Age-Related Issues at Diagnosis]