the least functional, and with the most suspicious features,
or the largest if they look benign.5
FNA biopsy results are categorized as nondiagnostic,
malignant, suspicious for malignancy (50%-75% risk),
indeterminate or suspicious for neoplasm (20%-30%
risk), follicular lesion of undetermined significance
(5%-10% risk), and benign.5
Nondiagnostic cytology
occurs in samples that fail to meet cytologic adequacy,
which requires at least 6 follicular-cell groups, each
containing 10 to 15 cells from at least 2 different aspirates
of a nodule. In such a case, a repeat ultrasound-guided
FNA should follow.5
However, 7% of
nodules can continue to yield nondiagnostic cytology
results that may be malignant, so these nodules should
be closely monitored by serial ultrasound or surgery.5
Surgery should be more strongly considered with solid
nodules. Indeterminate cytology (suspicious for follicular
or Hürthle-cell neoplasm, or follicular lesion of undetermined
significance) has an increased risk for malignancy,
ranging from 15% to 30%; so, the use of molecular markers
can be considered to guide management.5
The American
Thyroid Association also recommends thyroid lobectomy
for patients with an indeterminate solitary
nodule, and total thyroidectomy for large tumors >4 cm
and patients who have a high-risk history for malignancy.5
All cytology suggesting malignancy requires surgery
with either lobectomy or total thyroidectomy, unless
there are contraindications or diffuse metastasis.
Finally, if a nodule is benign on cytology, no further
immediate workup or treatment is required. Serial ultrasound
examinations should be performed every 6 to 18
months to monitor for growth. If there is a more than
50% change in volume or a more than 20% increase in
at least 2 dimensions, with a minimal increase of 2 mm
in solid nodules, a FNA biopsy should then be repeated.