What are tumors?

A tumor is defined as a swelling or morbid enlargement that results from an overabundance of cell growth and division; normally cells grow and divide to produce new cells in a controlled and orderly manner.

Although often used as a synonym for neoplasm, the word tumor is not synonymous with cancer. Tumors may be benign, pre-malignant, or malignant, or can signify a lesion with no cancerous potential.

Benign tumor:

A benign tumor is a non-cancerous tumor. Benign tumors do not invade nearby healthy tissue or spread throughout the body.

An example of a benign tumor is a meningioma. Meningiomas stem from the membranes surrounding the brain and spinal cord. While the majority of meningiomas are benign, there are cases that are malignant or atypical, which is when the tumor is neither benign nor malignant but is somewhere in between.    

Malignant tumor:

A malignant tumor is a cancerous tumor. Malignant tumors have cells that are abnormal and divide uncontrollably without order. These cells are often spread to and damage nearby tissue and may spread to other parts of the body, which is known as metastases.

Malignant tumors are classified by the type of cancer they present, based on their appearance under a microscope and their pattern of growth. Some tumors are caused by genetic mutations.

Tumor classification systems:

• 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

Diagnostics and treatment

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 (reducing tumor in size) or surgical removal. Cancerous tumors may be treated with chemotherapy, radiation, or surgery by an oncologist and health care team.

Tumors vs cysts

Tumors should not be confused with cysts, which are distinct but can be similar.

While a tumor is an abnormal mass of tissue, a cyst is a sac containing air, fluid, or other material. In addition, while a tumor may be benign or malignant, most cysts are noncancerous. Removing and studying a sample of the tissue in question — known as a biopsy — can determine whether a bump is either a tumor or a cyst.