Thyroid Nodule Disease: “Don’t sweat the small stuff.”

By Daniel S. Duick, MD, FACP, FACE

The thyroid gland is located in the lower half of the neck in the midline - in the front of the wind pipe, below the voice box (larynx) and above the breast bone (sternum). The butterfly shaped gland produces thyroid hormone to help regulate body metabolism and maintain all body tissues and systems. The thyroid can develop a number of structural abnormalities. The entire thyroid may enlarge, which is known as a goiter. A single lump or nodule may appear without the remainder of the thyroid becoming enlarged. Multiple nodules may be present in an enlarged gland known as a multinodular goiter.

Another term for nodule is tumor. Either term raises a patient's immediate concern about cancer. Yet, the actual overall risk of a thyroid nodule being malignant is actually quite small - about 1 out of every 20 nodules or 5% of diagnosed nodules are eventually proven to be malignant or cancerous.

Certain features of a patient's history, physical findings and ultrasound imaging findings may suggest an increased risk or greater than a 5% average chance of malignancy:

History

  • Family members with thyroid cancer
  • Prior neck radiation therapy
  • Prior malignancy of another kind
  • Hoarse voice

Physical findings

  • A "hard" nodule
  • A "fixed" nodule that does not move when a physician pushes it with his or her fingers

Ultrasound Features

  • Microcalcifications
  • Increased blood flow within a nodule detected by Doppler flow imaging.
  • Irregular margins

A Diagnostic Ultrasound exam is the key test to establish whether a nodule may or may not need a diagnostic Fine Needle Aspiration Biopsy (FNAB). FNAB as the name indicates uses a very thin needle to sample a nodule. It is a procedure that is generally very well tolerated by patients. Selection is important. Women over 40 have a 40-50% chance of having one or more nodules detectable on ultrasound that are "small" or 10 millimeters or less in diameter, which is slightly smaller than a dime (a dime is 13 millimeters in diameter). Moreover, the great majority of these nodules is benign and can be monitored over time without the need for aspiration biopsy. If the nodule enlarges, FNAB may be indicated.

A small thyroid nodule that could be cancerous does not have the same implications as a similar size nodule found in the breast or prostate. In the latter instances there is generally a far greater chance of a rapidly progressing and spreading malignancy. Even more astounding is the fact that the most common type of thyroid cancer, papillary thyroid cancer that comprises 80 to 90 % of all newly diagnosed and treated cases annually may have already been present for 10 to 20 years or more.

How do we know this and why do we say the risk is very small for thyroid nodules that are 10 millimeters or smaller? Interestingly, numerous autopsy series of adults dying at all ages from another cause (such as auto accidents) have demonstrated the prevalence of these small cancers (6-16 %) and no difference in rates in 20-30 year olds versus any later decade in life. Thus, at any given time in adulthood, seventeen to twenty million or more Americans are walking around with an "incidental,” “silent," and seldom progressive, 10 millimeter or less thyroid cancer in their neck, which will most likely never progress and become a problem in their lifetime. It is estimated that the number of these tumors that continue to enlarge is only around 1-2 % while 98-99% remain silent and non-problematic throughout adulthood.

“…At any given time in adulthood, seventeen to twenty million or more Americans are walking around with an “incidental,” “silent,” and seldom progressive, 10 millimeter or less thyroid cancer in their neck, which will most likely never progress and become a problem in their lifetime.”

When a larger thyroid nodule is found and is greater than 20 millimeters or 2 centimeters, the same proportion, about 1 in 20 are malignant, but the risk begins to climb. Although the ability to cure such cancers is still high it is lower than it is for smaller cancers. Whenever fine needle aspiration biopsy material in smaller (but growing) nodules or in larger nodules is diagnostic of cancer or raises the possibility that cancer is present, denoted by the terms "indeterminate" or "suspicious," surgery is recommended for therapeutic or diagnostic reasons.

Additional information related to thyroid nodules and thyroid cancer can be located at the AACE Power of Prevention website at www.powerofprevention.com by simply clicking on the Quick Links section related to thyroid diseases.

Daniel S. Duick, MD, FACP, FACE, is the Immediate Past President of the American Association of Clinical Endocrinologists. He is an Illinois native and graduated from Northwestern University Medical School. He completed his medical residency and endocrinology fellowship training at both USC – Los Angeles County Hospital and Walter Reed Army Medical Center before serving two years of active duty in the Army. He subsequently joined the staff of Mayo Clinic (Rochester, MN) before moving to Phoenix, Arizona, where he served as the Director of the Internal Medicine Residency Training Program for 12 years at St Joseph’s Hospital and Medical Center. Dr. Duick then joined Endocrinology Associates, PA, in private practice in Phoenix. Dr. Duick has been an active and influential member of AACE. As Immediate Past President, Dr. Duick serves on the Board of Directors, as well as various AACE committees.