NCI Dictionary of Cancer Terms

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The NCI Dictionary of Cancer Terms features 7,846 terms related to cancer and medicine.

Browse the dictionary by selecting a letter of the alphabet or by entering a cancer-related word or phrase in the search box.

The abnormal growth of breast gland tissue in males. Gynecomastia in infants and boys may be caused by an imbalance in certain hormones. It may also be caused by conditions that affect hormones, such as tumors; malnutrition; kidney, liver, or thyroid disease; or treatment with certain drugs. It can occur at any age.