Why can benign tumors still be dangerous?
Dr. Jack Merendino, MD
Endocrinology Diabetes & Metabolism
We should start by emphasizing that most benign tumors are not dangerous. Having said that, a tumor can cause problems by where it is located or by how large it is. For example, a benign pituitary tumor may cause problems because it is large and is pressing on the optic nerve in the brain, causing vision loss. Or a large thyroid tumor may be compressing the trachea, causing breathing problems. I’ve mentioned endocrine tumors because that’s my specialty, but these same considerations may apply to non-endocrine tumors. One thing that is specific to endocrine tumors, however, is over-production of hormones. Many benign tumors cause problems because they are producing hormones in amounts that are too large or in ways that are not properly regulated. A common example of this would be a pituitary tumor that is making too much prolactin. These tumors are almost never cancerous and they are usually not that large, but they often cause problems because the excess prolactin leads to breast enlargement in men or breast milk production in both men and women, and too much prolactin often causes irregular periods and infertility in women or a low testosterone level in men.  
Dr. Michael Roizen, MD
Internal Medicine
Some tumors don't have cancer cells; this means that they're benign. However, the dictionary definition of 'benign' doesn't apply perfectly here, because a benign tumor can still be dangerous. Why? Benign tumors can grow to block off the pathway of important nutrients and bloody supply throughout the body. That's why surgery is sometimes necessary to remove benign tumors-to re-open the roads for nutrients to get to the organs.
YOU: The Owner's Manual, Updated and Expanded Edition: An Insider's Guide to the Body that Will Make You Healthier and Younger

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YOU: The Owner's Manual, Updated and Expanded Edition: An Insider's Guide to the Body that Will Make You Healthier and Younger

Between your full-length mirror and high-school biology class, you probably think you know a lot about the human body. While it's true that we live in an age when we're as obsessed with our bodies as...

Continue Learning about Thyroid


A member of our endocrine system, the thyroid gland produces hormones that help control many of our body functions, such as weight and temperature.Located at the base of our neck, this butterfly-shaped gland makes several hormones...

, which are collectively known as thyroid hormones. These hormones are especially key in the brain development of infants and children. Thyroxine, also known as T4, is the primary hormone secreted by the thyroid gland; this hormone helps control our metabolism, a chemical process that turns our food into energy. A lack of iodine in your food can cause the thyroid to swell, a condition called a goiter. Several other disorders and diseases can affect this gland, including cancer. If you notice swelling in your neck or feel a lump, make sure you see your doctor; this could indicate a problem with this important gland.

Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.