Q: After she found a lump in my thyroid gland, my internist sent me to an endocrinologist, who put a needle into the lump and told me that surgery was not necessary because the lump was not cancerous. I am still concerned about the possibility of thyroid cancer and would like to know more about the reliability of the procedure that was performed.
A: The procedure performed by your endocrinologist, called a fine needle aspiration, is now the most common technique used to diagnose the cause of lumps in the thyroid gland. In this procedure a small needle attached to a syringe is inserted in the thyroid mass; by applying suction through the syringe, small bits of thyroid tissue are pulled into the needle and syringe.
The tissue is examined under a microscope to diagnose whether cancer is present and to determine the type of cancer. An unsatisfactory specimen is obtained in as few as 5 percent or as many as 25 percent of aspirations, depending on the skill and experience of the doctor.
Approximately 10 percent to 20 percent of satisfactory aspirations are positive or suspicious for cancer. In most cases of such findings, surgical removal is recommended to make a definitive diagnosis.
In about two-thirds of fine needle aspirations, the diagnosis of a benign condition is made, as it was in your case. The chance that you might have a thyroid cancer, despite the diagnosis of a benign condition, is quite small; but the presence of a cancer is missed in about 5 percent to 10 percent of the needle aspirations.
Your doctor has probably placed you on thyroid hormone to reduce the further growth of a benign lump. It is important for you to return for further examinations. If the size of the lump continues to increase during follow-up, surgical removal of the .. mass may become necessary.
Dr. Margolis is professor of medicine and biological chemistry at the Johns Hopkins School of Medicine.