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.
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.
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.
The tumor grade system is most often used to classify a tumor; 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
Diagnosis 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 for 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.
Tumor lysis syndrome
Tumor lysis syndrome occurs when tumor cells are released into the bloodstream spontaneously or in response to cancer treatment. This may result in hyperuricemia, hyperkalemia, hyperphosphatemia and hypocalcemia. In some cases, these electrolyte and metabolic disruptions may progress to renal insufficiency, cardiac arrhythmias, seizures or death from multi-organ failure.
Tumor lysis syndrome is the most common disease-associated emergency that physicians come across when treating children and adults with hematologic cancers. The syndrome most often occurs in patients with non-Hodgkin’s lymphoma or acute leukemia. However, the frequency of tumor lysis syndrome is increasing among patients with tumors that were rarely associated with the syndrome.
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