Contents
What is a tumor?
Definition of a Tumor
A tumor basically means a swelling. The medical definition of a tumor as a swelling or a lesion which results from the abnormal growth of cells that persists even after the initiating stimulus has been removed. A tumor can be benign or malignant based on the behavior of the cells that make up the tumor.
What is a benign tumor?
Non-Cancerous Growth
Benign tumors are slow growing lesions which remain localized to the site of origin. This means that it does not spread into adjacent tissue. A benign tumor is NOT cancer. There are different types of benign tumors that are named according to the site where it occurs.
- Epithelial tumors are either papillomas (arising from non-secretory epithelium) or adenomas (arising from secretory epithelium).
- Mesenchymal and connective tissue tumors are usually named according to the tissue of origin and appended with the suffix ‘oma’. For example lipoma is a benign tumor arising from fat cells of lipid tissue or osteoma from bone tissue. However, there are several exceptions like lymphoma, myeloma which are malignant tumors or tuberculoma which is a lesion in tuberculosis.
Characteristics of a Benign Tumor
These are slow growing tumors made up of cells that closely resemble the parent cells of the organ or tissue of origin. The benign tumors do not spread to surrounding tissue or to distant sites in the body. The nucleus of the benign tumor cells remains normal and the border of the tumor is well defined or sometimes encapsulated. Some long standing benign tumors may turn malignant eventually.
Effects of Benign Tumors
Even though benign tumors are confined to its site of origin, it can lead to certain clinical complications.
- It can cause pressure effects on the adjacent tissues. For example, a benign tumor of the pituitary gland can cause visual disturbances by compressing the optic nerve.
- A benign tumor can secrete hormones. For example, a benign tumor of the thyroid gland can cause thyrotoxicosis (excess of thyroid hormones) or a gastrinoma (stomach) can secrete gastrin leading to high gastric acid production.
- Sometimes a benign tumors can transform into malignant tumor (cancer). For example, adenomatous polyps of the colon can progress to adenocarcinoma of colon (colon carcinoma).
- Benign tumors can physically impede the normal functioning of certain organs. For example, a large lipoma near a joint can interfere with full mobility of the joint while a large fibroid of uterus may interfere with normal labor.
- Benign tumors can cause some psychological impact – depression due to cosmetic reasons or anxiety because of fear about the tumor turning dangerous.
What is a malignant tumor?
Cancerous Growth
Malignant tumors are lesions with uncontrolled growth that invades surrounding tissues and spreads to distant sites. The pattern of growth and invasion is the reason that a malignant tumor or malignancy is known as cancer.
- Malignant epithelial tumors are called carcinomas like squamous cell carcinoma or adenocarcinoma.
- Malignant tumors of connective tissue are called sarcomas like liposarcoma, fibrosarcoma or osteosarcoma.
- Malignancy of the blood is called leukemia and that of lymphoid tissue is known as a lymphoma.
Some tumors do not fall into either of the classical groups and are often referred to as borderline tumors.
Characteristics of Cancer
Malignant tumors are fast growing lesions. The cells resemblance of the parent cells of the organ or tissue of origin is highly variable and often the resemblance is poor. It divides rapidly. The malignant cells have hyperchromatic nucleus with an irregular outline, multiple nucleoli and are pleomorphic. It can invade the surrounding tissue and spread to distant sites (metastases). The border of the malignant tumor is poorly defined or irregular. There may be necrosis or ulceration in the malignant tissue.
Effects of Cancer
Malignant tumors are extremely harmful, cause significant damage and often leads to death if left untreated.
- A malignant tumor can compress the adjacent tissue and directly invade the area.
- It may spread to distant sites and form secondary tumors (metastases).
- Some cancer can lead to hemorrhage and subsequent blood loss from ulcerated surfaces like colon cancer.
- Tumors of hollow organs can lead to obstruction of the lumen and affect the movement of substances through these cavities. For example, a malignant tumor of esophagus, stomach or colon can cause obstruction to passage of food and feces.
- Some malignant tumors also produce hormones like ACTH from certain lung tumors.
- Cancers usually cause weight loss and debility (cancer cachexia)
- Cancers are often associated with severe pain in late stages.
- Malignant tumors tend to cause serious psychological trauma, particularly associated with fear and depression of impending death and recurrence.
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