A tumor is defined as a
swelling or morbid enlargement. Although often used as a synonym for neoplasm,
the word tumor is not synonymous with cancer; tumors may be benign
(non-cancerous), pre-malignant or malignant (cancerous), or can signify a
lesion with no cancerous potential.
A tumor results from an overabundance of cell growth and
division; normally cells grow and divide to produce new cells in a controlled
and orderly manner. In malignant tumors (that is, cancerous tumors), cells are
abnormal and divide uncontrollably and without order. Often these cells spread
to and damage nearby tissue and may spread to other parts of the body
(metastases).
Tumors vary in type and size, and the type of tissue
they occur in often signifies their shape and how they grow. Medulloblastoma,
for example, begins in embryonic cells (blastoma) in the inner part of the
brain (medulla). Diagnosis is based on the type and location of the tumor. This
is performed using tumor marker tests and imaging studies. Some tumors, such as
those on the exterior of the skin, are visible and may be palpated with the
hands.
Similar to diagnosis, treatment is based on the location
and type of tumor. Benign tumors often require no treatment, or may require
debulking (that is, reducing the tumor in size) or surgical removal. Cancerous
tumors may be treated with chemotherapy, radiation or surgery by an oncologist
and health care team.
Malignant tumors are classified by the type of cancer
they present, based on their appearance under a microscope and their pattern of
growth. The tumor grade system is most often used; this includes histologic and
nuclear grade.
There are five grades used in classification:
- GX: Tumor grade is not able to be assessed
- G1: Well defined cells; good prognosis
- G2: Somewhat differentiated cells; medium grade
- G3: High grade of poorly differentiated cells
- G4: Highest grade; undifferentiated
Some tumors are caused by genetic
mutations.
Additional information can be found by searching the following
websites:
www.cancer.gov
www.ncbi.nlm.nih.gov
http://www.ctf.org/
www.cancer.org