Adenomas: The Benign Tumors That Grow in Your Glands and Organ Linings — Types, Risk, and Treatment
Updated: 2 days ago
Medically reviewed by Dr. Baraa Alnahhal, MD · Last reviewed: September 2026
TL;DR
An adenoma is a benign (noncancerous) tumor that grows in the epithelial tissue lining your glands and organs. Adenomas grow slowly and often look like small mushrooms with stalks — they are a type of polyp, also called an adenomatous polyp. By definition they are not cancer, but larger adenomas can sometimes turn into cancer, which is why providers usually remove polyps larger than 5 millimeters and monitor smaller ones. They can form anywhere there is glandular tissue — the colon, adrenal glands, parathyroid glands, pituitary gland, salivary glands, and oil-producing glands — and some ("functioning" adenomas) secrete excess hormones. With treatment, the outlook is typically very good, and most adenomas never become cancer.
Quick Answer
What it is: An adenoma (pronounced "add-a-NO-muh") is a benign, noncancerous tumor that starts in the epithelial tissue covering your organs and glands. It grows slowly, often shaped like a small mushroom with a stalk, and is also known as an adenomatous polyp.
Where it grows: Adenomas most commonly form along glandular organs — adrenal, colon, parathyroid, pituitary, salivary, and sebaceous glands — and can be functioning (secreting excess hormones) or nonfunctioning (producing no hormones and possibly causing no symptoms).
Cancer risk: By definition adenomas are noncancerous, but they can sometimes turn into cancer, especially larger ones. Cauliflower-like (advanced) adenomatous polyps larger than 10 millimeters carry the most concern, which is why providers usually remove polyps larger than 5 millimeters.
Outlook: With treatment the outlook is typically very good — many adenomas respond well and never turn into cancer. Small adenomas may be watched ("active surveillance"), hormone problems may be treated with medication, and prevention centers on regular cancer screenings, avoiding smoking, and a diet rich in fruits, vegetables, and whole grains.
What Is an Adenoma?
An adenoma (pronounced "add-a-NO-muh") is a benign (noncancerous) tumor. Adenomas start in epithelial tissue — the tissue that covers your organs and glands. These tumors grow slowly and look like small mushrooms with stalks.
Adenomas are a type of polyp. In fact, another name for an adenoma is an adenomatous polyp.
By definition, adenomas are noncancerous. But they can sometimes turn into cancer, especially larger ones. That is why it is important for a healthcare provider to monitor adenomas and treat them when necessary.
What Are the Six Types of Adenomas?
Adenomas most commonly grow along your glandular organs — the organs that produce and release chemicals called hormones, which regulate many of your body’s functions. There are six recognized types:
Type | Where It Grows | Key Detail |
Adrenal adenoma | Adrenal glands | Forms on the adrenal glands |
Colon adenoma | Colon lining | A type of colon polyp; cauliflower-like adenomatous polyps larger than 10 millimeters are called advanced adenomas |
Parathyroid adenoma | Parathyroid glands | Causes overproduction of parathyroid hormone |
Pituitary adenoma | Pituitary gland | May be microadenomas (smaller than 1 centimeter) or macroadenomas (larger than 1 centimeter) |
Pleomorphic adenoma | Salivary glands | Forms in the salivary glands |
Sebaceous adenoma | Oil-producing glands | Grows along the skin’s oil-producing glands |
Functioning vs. Nonfunctioning Adenomas
Adenomas can also be classified by whether they produce hormones:
Type | What It Does |
Functioning adenoma | Secretes excess hormones, which can disrupt the body’s functions |
Nonfunctioning adenoma | Does not produce hormones at all — you might not have any noticeable symptoms |
How Are Adenomas Categorized by Growth Pattern?
Healthcare providers categorize adenomas based on how they grow:
Growth Pattern | Description | Typical Setting |
Tubular | Grows in a round or oval shape | Most common in small adenomas under 0.5 inches (1.27 centimeters) |
Villous | Grows in a shaggy, cauliflower-like pattern | Most common in larger adenomas |
Tubulovillous | A mixture of tubular and villous growth patterns | In-between cases |
Sessile | Grows in a flattened shape with a larger base (instead of a stalk) | Instead of a stalk-like base |
Serrated | Has a saw-tooth pattern under a microscope | Identified by pathologists |
Sessile serrated | A mixture of sessile and serrated growth patterns | Combined pattern |
What Are the Symptoms of an Adenoma?
Symptoms vary depending on the location. Small adenomas may not cause any symptoms at all. General signs and symptoms may include:
Symptom | Notes |
Abdominal pain | Often associated with colon adenomas |
Fatigue | A general, nonspecific sign |
Headache | Common with pituitary adenomas |
Iron-deficiency anemia | Can result from slow colon bleeding |
Muscle weakness | Often tied to hormone-disrupting adenomas |
Nausea or vomiting | A general sign of an adenoma causing problems |
Rectal bleeding | A warning sign associated with colon polyps |
Because nonfunctioning and small adenomas may produce no symptoms at all, screening — not symptom-watching — is how most adenomas are found.
What Causes Adenomas?
Adenomas develop when cells grow and divide uncontrollably instead of following your body’s instructions for programmed cell death. This is how cancerous tumors form, too. But adenomas are less aggressive than cancer and they grow more slowly.
What Are the Risk Factors?
Several factors can increase your risk of developing adenomas:
Risk Factor | How It Raises Risk |
Age | Adults in their 30s or 40s are more likely to develop pituitary adenomas |
Ethnic background | People of Ashkenazi Jewish descent have a higher risk of adenomas |
Gene variations | Genetic conditions like multiple endocrine neoplasia type 1 (MEN1) make adenomas more likely; these variations are hereditary |
Genetic diseases | Some causes, like familial adenomatous polyposis (FAP), run in families |
Sex | Women are twice as likely to develop parathyroid adenomas |
What Are the Complications?
Even though adenomas are benign tumors, they can lead to health complications. Some adenomas press on surrounding organs or disrupt hormone production as they grow. The severity of an adenoma can vary depending on its size and location.
How Are Adenomas Diagnosed?
To diagnose an adenoma, your healthcare provider will do a physical exam and review your medical history. They may also need imaging tests, including:
Diagnostic Step | Purpose |
Physical exam and medical history | Establishes symptoms and risk factors |
CT scan | Images internal organs to locate growths |
MRI scan | Detailed imaging, especially useful for pituitary adenomas |
PET scan | Imaging that can reveal metabolic activity of tissue |
Biopsy | A small tissue sample is sent to a laboratory, which analyzes it and rules out or confirms the presence of an adenoma |
How Are Adenomas Treated?
Adenoma treatment depends on size, location, and whether it causes health problems:
Treatment | When It Is Used |
Medication | If the adenoma causes hormone problems |
Surgery | Providers usually remove polyps larger than 5 millimeters because larger adenomas are more likely to become cancerous; surgery may also be recommended if the adenoma causes significant health problems |
Active surveillance | A "watch-and-wait" approach if an adenoma is small and does not cause any health complications |
What Is the Outlook?
If you receive treatment for an adenoma, the outlook is typically very good. Many types of adenomas respond well to treatment and do not turn into cancer.
Learning that you have a growth can be scary, and "Is it cancerous?" is usually the first question. Adenomas are not cancer, and they usually do not turn into cancer. Cancer screenings and preventive care, such as surgical removal, reduce your risk of future problems.
Can Adenomas Be Prevented?
Adenomas are not always preventable because you cannot always control the risk factors. But you can improve your chances of staying healthy through regular cancer screenings — if you have a higher risk, ask your provider how often you should be screened.
You can also support your overall health by:
Preventive Habit | Why It Helps |
Avoiding smoking | Reduces overall cancer and polyp risk |
Eating plenty of fruits, vegetables, and whole grains | Supports colon and glandular health |
Increasing physical activity | Improves overall metabolic health |
Limiting alcohol intake | Lowers cancer risk factors |
Living With an Adenoma
Some adenomas — like ones in the colon — carry a higher risk of cancer. It is important to seek treatment right away if you think you have an adenoma. Having a colonoscopy when your provider recommends it can catch adenomas while they are small.
Conclusion
An adenoma is a word that sounds alarming but usually describes something manageable: a benign, slow-growing tumor shaped like a small mushroom, arising from the epithelial lining of glands and organs throughout the body. Six types grow in six different places — the colon, the adrenal glands, the parathyroid and pituitary glands, the salivary glands, and the skin’s oil glands — and each one can be functioning (pumping out excess hormones) or nonfunctioning (sneaking by with no symptoms at all). The critical nuance is size: by definition these tumors are noncancerous, yet larger ones can sometimes turn into cancer, which is why the 5-millimeter surgical threshold exists and why cauliflower-like polyps larger than 10 millimeters earn the label "advanced adenomas." Finding them early is a screening game, not a symptom game, and prevention rests on the familiar pillars of avoiding smoking, eating well, moving more, and limiting alcohol. With treatment, the outlook is typically very good, and most adenomas never become cancer.
CTA: If you are 45 or older, have not had a colonoscopy, or have a family history of adenomas, familial adenomatous polyposis (FAP), or MEN1, schedule a screening conversation with your healthcare provider this month. If you have already been told you have an adenoma, ask directly: How big is it? Is it functioning or nonfunctioning? What growth pattern does it have? And what is my screening schedule going forward? Early detection at the small, polyp stage is the single most powerful lever for a very good outcome.
Questions to Ask Your Provider
How often do I need screenings?
What can I do to lower my risk of developing another adenoma?
What symptoms should I watch for?
How does having an adenoma affect my overall health risks?
Frequently Asked Questions
What is an adenoma?
An adenoma (pronounced "add-a-NO-muh") is a benign (noncancerous) tumor that starts in epithelial tissue — the tissue that covers your organs and glands. Adenomas grow slowly, often shaped like small mushrooms with stalks, and are a type of polyp also known as an adenomatous polyp.
Are adenomas cancer?
No. By definition, adenomas are noncancerous tumors. However, they can sometimes turn into cancer, especially larger ones. This is why providers monitor adenomas closely and usually remove polyps larger than 5 millimeters.
Where do adenomas grow?
Adenomas most commonly grow along glandular organs. The six main types are adrenal adenomas (adrenal glands), colon adenomas (colon lining), parathyroid adenomas (parathyroid glands, which overproduce parathyroid hormone), pituitary adenomas (pituitary gland — under or over 1 centimeter in size), pleomorphic adenomas (salivary glands), and sebaceous adenomas (oil-producing glands).
What is the difference between a functioning and a nonfunctioning adenoma?
A functioning adenoma secretes excess hormones, which can disrupt the body’s functions. A nonfunctioning adenoma does not produce hormones at all, so you might not have any noticeable symptoms.
What are the symptoms of an adenoma?
Symptoms depend on location, and small adenomas may cause none at all. General signs include abdominal pain, fatigue, headache, iron-deficiency anemia, muscle weakness, nausea or vomiting, and rectal bleeding. Because nonfunctioning adenomas often cause no symptoms, regular screenings are how most are discovered.
What causes adenomas?
Adenomas develop when cells grow and divide uncontrollably instead of following the body’s instructions for programmed cell death — the same basic process that forms cancerous tumors. Adenomas differ in that they are less aggressive and grow more slowly than cancer.
How are adenomas treated, and what is the outlook?
Treatment options include medication for adenomas that cause hormone problems, surgery — typically for polyps larger than 5 millimeters, since larger adenomas are more likely to become cancerous — and active surveillance (watch-and-wait) for small adenomas causing no problems. With treatment, the outlook is typically very good: most adenomas respond well and never turn into cancer.
Related Reading
Sources
Medical Disclaimer
This article is for general informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Adenomas are benign tumors that can sometimes turn into cancer — particularly larger ones — and some adenomas in the colon carry a higher risk of malignancy. Only a licensed healthcare provider can diagnose an adenoma through physical examination, imaging, and biopsy, and determine whether watch-and-wait surveillance, medication, or surgical removal is appropriate for your case. Rectal bleeding, unexplained iron-deficiency anemia, persistent abdominal pain, or new hormone-related symptoms warrant prompt medical evaluation. Never delay seeking medical care because of something you have read here.
Comments