Glossary of Cancer Terms

Ocular Melanoma A cancer that occurs in the pigmented areas of the eye. It is associated with exposure to ultraviolet light.


Tumors which arise from oligoendrocytes, a type of supportive brain tissue. Most frequently occur in young and middle-aged adults but also found in children. Represents about 4% of all primary brain tumors.

Ommaya reservoir

A device with a fluid reservoir implanted under the scalp with a catheter to a ventricle. It allows for medication to be given directly to the cerebral spinal fluid and into the brain.


The biological units that promote and maintain tumor cells. When an oncogene is activated, mechanisms within the cell that limit the growth of the cell become unbalanced. The oncogenes promote cell growth and survival, while tumor suppressor genes become inactivated. The effect is unchecked cell growth that may become a tumor.


A doctor who specializes in treating cancer. There are surgical, radiation, pediatric, gynecologic and medical oncologists. The term oncologist alone generally refers to medical oncologists who are internists with expertise in chemotherapy and handling the general medical problems that arise during the disease.

Oncology The medical specialty that deals with the diagnosis, treatment and study of cancer.

Oncology nurse

A nurse with special training in the care of cancer patients.

Oncology pharmacy specialist

A pharmacist who prepares anticancer drugs in consultation with an oncologist.

One-step procedure

Biopsy and surgical treatment combined into a single operation.

Onset of action

The length of time it takes for a medicine to start to work.


Pertaining to the eye.


A lighted instrument used to examine the inside of the eye, including the retina and the optic nerve.

Optic nerve

The nerve that carries messages from the retina to the brain.

Oral surgeon

A dentist with special training in surgery of the mouth and jaw.


Surgery to remove a testicle.


The area of the throat at the back of the mouth.


A condition which is characterized by softening of the bones, and bone loss.

Osteosarcoma Sarcomas are uncommon malignant tumors that begin either in bones or in soft tissues such as muscles, cartilage, fat or connective tissue. They make up about 1% of cancers in adults and 15% in children. They are classified based on the tissue of origin. The tissue of origin for osteosarcomas is the bone. Osteosarcomas primarily effect teenagers. There are three tumor categories related to the tumor's grade or activity; low, intermediate and high grade. High grade are the faster growing cancers.


An surgically formed artificial opening which serves as the exit site for connections which the surgeon has made from an area inside the body to the outside. The opening is called a stoma.

Ovarian Cancer Cancer of the ovary. One of the most common gynecologic malignancies. The most common type of ovarian cancer arises from the cells covering the surface of the ovary and is known as epithelial carcinoma. Two other major kinds of ovarian cancers are; germ cell, arising from the eggs, and ovarian stromal tumors, which arise from supportive tissue. These are relatively uncommon and account for less than 10% of ovarian malignancies.


One of two glands in the female that produce the reproductive cell, the ovum, as well as certain hormones, estrogen and progesterone. Singular is ovary.


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