The time may be very short between the first evidence of the presence of a tumor and the development of a condition which would render complete removal impossible.
The effect of a tumor upon its bearer depends upon its character and situation.

Pain is very commonly present, and is due to the pressure which the growing tumor exerts upon the sensory nerves.

Pain may, however, not be present or appear only at the last.

A condition of malnutrition and emaciation often results due to the passage into the blood of injurious substances formed in the tumor, or to the destruction of important organs by the growing tumor.

The growth of a tumor in the intestine may obstruct or close the canal and thus interfere with nutrition.
The cause or causes of tumors are unknown.