Mesotelioma is a misspelled variation of the word "mesothelioma." The only known cause for the cancer known as mesothelioma is exposure to asbestos. No one knows why some individuals who worked with asbestos develop the disease while others do not. Some doctors have hypothesized that prolonged exposure to asbestos for long lengths of time causes the disease but recently, especially after Sept. 11, researchers have discovered that large amounts of asbestos exposure for a short period of time may also prompt the disease to develop. Often, the disease is diagnosed in older individuals because it remains latent for up to 50 years. Lately, however, diagnoses have appeared in younger people who were exposed during childhood or those who encountered large amounts of toxic asbestos as first responders or clean-up personnel after the World Trade Center disasters. Mesothelioma is always fatal though treatment to ease symptoms is available.