Thyroid Nodules (cont.)
Fine Needle Aspirate Biopsy (FNAB)
- If a thyroid nodule is larger than 1 cm, or it has other worrisome
characteristics seen on ultrasound or other imaging tests, then FNAB may be
- This office procedure does not require anesthesia and consists of passing
small needles (similar to those used to draw blood from the arm) into the
thyroid nodule(s) in the neck. This is a quick and usually painless procedure.
- This procedure may be done on multiple nodules.
- Ultrasound guidance may be used to assist in the FNAB of nodules that are
bigger than 1.0 to 1.5 cm, but cannot be felt by physical examination.
- A sample of the contents of each nodule (to include fluid, blood, or tissue)
are removed in the needle and examined by the pathologist under a microscope.
- Pathologists often can identify certain features in the nodule sample.
FNAB results are characterized as one of the following:
- Benign: This is the most common outcome of FNAB.
The typical finding is a nodule filled with colloid protein, a normal component
of the thyroid. Benign nodules can be followed over time with serial physical
exams or ultrasound exams. Further intervention is only necessary if enlargement
occurs or new symptoms develop.
- Malignant: Some thyroid cancers can be diagnosed directly from FNAB
results (for example, papillary thyroid cancer). Other thyroid cancers
cannot be diagnosed from FNAB results (such as follicular
thyroid cancer). This is because the diagnosis rests not simply upon the appearance of
the tissue within the nodule, but also on the level of the invasion of surround
blood vessels and tissue by the nodule. For such nodules, surgical removal of a
portion or the entire thyroid is recommended.
- Indeterminate: This is neither definitively benign
nor malignant. Given that the risk for cancer is increased by 20% in such cases,
surgical removal of a portion or the entire thyroid is typically recommended.
Often, a radionuclide scan will be done to obtain functional information (determine
nodule is actively producing thyroid hormones) in order to avoid unnecessary
- Non-diagnostic: This means that there are not enough
of the tissue cells present in the sample to make a diagnosis. Non-diagnostic FNABs will typically result in repeat FNAB or definitive surgery.
Cystic nodules more often result in a non-diagnostic FNAB due to higher
fluid content than solid content in the sample obtained from the nodule.
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