An abnormal mass of
undifferentiated cells within a multicellular organism that results
from excessive cell division; term often used to designate
cancer.
A tumour is an abnormal tissue swelling or mass
that results when cells divide more than they should or do not
die when they should and continues to grow after the stimuli
which initiated the new growth cease.
Tumours perform no useful body function and can interfere with
vital body functions and absorb nutrients needed elsewhere. They
can be malignant (cancerous), which means they will grow rapidly
and spread to other parts of the body or cause more tumours to
form elsewhere, or be benign, which means that they will
generally grow much more slowly and stay put in one area.
A plant Tumour can be defined as a 'massive cellular growth
without cellular differentiation'.
