A benign (noncancerous) tumor that forms from the cells lining the inside or the surface of an organ.
Adenomas arise from cells that are specialized for secretion. These cells, called epithelial cells, are found throughout the body, but only a fraction is designed for secretion. This type of epithelial cell makes up specific organs and structures in the body known as glands. Glands produce sweat, saliva, mucus, milk, digestive juices, hormones, and an array of other substances. Hormone-secreting (endocrine) glands include the thyroid, pituitary, parathyroids, adrenals, and the ovaries and testes. Gland cells that secrete material outward through a duct, such as sweat glands and glands secreting digestive juices into the stomach and intestines, are called exocrine glands. Adenomas can arise from most of the gland cells in the body.
Adenomas result from excessive growth of normal epithelial cells. They arise in much the same way as malignant (cancerous) tumors but do not spread (metastasize) to nearby tissue or other parts of the body. New cells are normally created only when they are needed by the body. When the body does not need new cells and cell division continues, a mass or tumor is formed.
Tumors found on some glands are more likely to be adenomas than malignant tumors (carcinomas), including adrenal tumors, pituitary tumors, and salivary gland tumors. The adrenal tumor known as pheochromocytoma is benign in 90% of reported cases. The gastrinomas associated with Zollinger-Ellison syndrome are benign in 50% of patients with this condition. Adenomas are also associated with Cushing's syndrome, a disorder caused by excess levels of a hormone secreted by the adrenal glands. Although most cases are caused by a dysfunctional pituitary gland, 20-25% are due to adrenal adenomas.
The occurrence of an adenoma rarely indicates an increased chance for the later development of a carcinoma. However, colon cancer and rectal cancer are thought to arise from adenomas, and one type of lung
Most adenomas affect the normal functioning of the organ or gland in which it arises, although some have no effect. Many secrete hormones, leading to elevated hormone levels in the blood and causing uncomfortable and sometimes life-threatening conditions.
Certain types of adenomas are more common in women than in men (e.g., pituitary tumors and liver adenoma), and some are more common in older adults (e.g., adenomas of the colon). But specific demographics depend on the specific type of adenoma.
Causes and symptoms
No single set of symptoms can be applied to all adenomas. Some disorders have similar or identical symptoms whether due to an adenoma or carcinoma. Ultimately, the signs and symptoms depend on the location of the adenoma:
- Adrenal glands: an adrenocortical adenoma often shows the same symptoms of an adrenocortical carcinoma, including abdominal pain and loss of weight. A benign and malignant pheochromocytoma also has the same symptoms, including headaches, sweating, and chest pains.
- Breast: a marble-like benign fibroadenoma causes no symptoms and is either too small to detect by touch or is several inches across and easily detected.
- Colon or rectum: persistent diarrhea can indicate villous adenomas of the rectum. Blood in stool samples can indicate adenomas in the colon or rectum.
- Liver: a hepatic adenoma causes pain and a mass that is detectable by touch.
- Lung: a chronic or bloody cough, fever, chills, and shortness of breath can indicate a bronchial adenoma.
- Pancreas: pain in the abdomen, diarrhea, stomach pain, persistent fatigue, fainting, and weight gain can indicate one of the various types of pancreatic adenomas or pancreatic cancer.
- Parathyroid: weakness, fatigue, constipation, kidney stones, loss of appetite, and bone pain are signs of a condition known as hyperparathyroidism, which occurs in patients with parathyroid adenomas or parathyroid cancer.
- Salivary gland: adenomas are small and usually painless but can cause swelling around the chin or jawbone, numbness of the face, and pain in the face, chin, or neck.
- Stomach and intestine: a gastrinoma causes a peptic ulcer in the intestines or stomach. The occurrence of many ulcers in the stomach, intestine, and pancreas that do not respond well to treatment can indicate Zollinger-Ellison syndrome.
- Sweat gland: adenomas may appear as many small, smooth, and firm bumps on the lower eyelids and upper parts of the cheek (syringomas), or as small bumps with bluish or dark-brown coloration on the head and neck area (hidrocystoma). Solitary adenomas (poromas) occur on the sole of the foot or palm of the hand.
- Thyroid: a lump in the neck region accompanied by a cough and difficulty swallowing or breathing often indicates a benign thyroid nodule; however, these are the same symptoms for thyroid cancer.
A variety of techniques is used to diagnose adenomas. Blood and urine samples are taken to detect elevated levels of hormones or other substances associated with a specific adenoma. Tumors are located using a combination of ultrasonography, computed tomography scan (CT scan), magnetic resonance imaging (MRI), and possibly radionuclide imaging. A biopsy is performed to determine whether a tumor is benign or malignant.
A doctor who interprets tissue samples (a pathologist) and a doctor trained in examining x rays and computer images (a radiologist) will make an initial diagnosis. Adenomas are often surgically removed, so a surgical team consisting of an anesthesiologist, surgeon, and nurses is often associated with treatment.
Clinical staging, treatments, and prognosis
Surgical removal is the recommended treatment for most adenomas, although the symptoms of some adenomas, such as pituitary tumors, can be treated with medication. In most cases, treatment cures the condition.
Two clinical trials completed in mid-2001 investigated treatments to prevent colon cancer in patients who have had surgery to remove adenomas of the rectum or colon. An 800 mg daily dose of folic acid may decrease the occurrence of colon cancer in patients who have had adenomas removed. The combined use of two drugs that are prescribed for other conditions, eflonithine and sulindac, may prevent the development of adenomas or the recurrence of colon cancer.
DeVita, Vincent T. Jr., Samuel Hellman, and Steven A. Rosenberg, eds. Cancer: Principles and Practice of Oncology. Philadelphia: Lippincott-Raven Publishers, 1997.
Greenspan, Francis S., and Gordon J. Strewler. Basic and Clinical Endocrinology. Stamford, Connecticut: Appleton&Lange, 1997.
Monica McGee, M.S.
—Two glands, one located above each kidney, that secrete hormones to prevent inflammation and to help regulate blood pressure, blood sugar levels, and metabolism.
—A malignant (cancerous) tumor that forms from the cells lining the inside or the surface of an organ. They tend to spread to other tissues and organs.
—A type of tissue that is composed of epithelial cells. It covers the outer and internal surfaces of the body and forms glands and parts of the sense organs.
—Four glands found in the neck area, with a pair on either side of the thyroid. They produce parathyroid hormone, which controls the level of calcium in the blood.
—A small gland found at the base of the brain. It is an important endocrine gland because it secretes many different hormones that control the activity of other endocrine glands.
—A gland located at the base of the neck. It secretes hormones that are essential for the regulation of body temperature, heart rate, metabolism, the level of calcium in the blood, and the level of calcium absorption by the bones.
QUESTIONS TO ASK THE DOCTOR
- Does the occurrence of this adenoma increase my chances of developing cancer?
- If I choose to have the adenoma surgically removed, what are the chances that I will develop another adenoma?
- Will all my symptoms disappear once the adenoma is removed?