Thyroid and Parathyroid

When a cyst is encountered on FNAC it should be drained completely, which is
curative in about 75 percent of simple cysts (Fig. 36-20), although some require a
second or third aspiration. If the cyst persists after three attempts at aspiration,
unilateral thyroid lobectomy is recommended. In cases in which the cyst is larger than
4 cm in diameter or is complex (i.e., has solid and cystic components), thyroid
lobectomy is recommended, because these cysts have a higher incidence of
.( malignancy (15 percent
Thyroid Imaging
Ultrasonographic Imaging
Ultrasound evaluation of the thyroid gland is helpful for detecting nonpalpable
nodules and for differentiating solid from cystic nodules. It provides a noninvasive
and inexpensive method of following the size of suspected benign nodules diagnosed
by FNAC. This is especially useful in determining whether the nodule or the
surrounding normal thyroid tissue decreases in size when the patient is treated with
thyroid hormone. Ultrasonographic imaging has no role in screening for thyroid
. nodules in asymptomatic patients
CT and MRI
Computed tomography and magnetic resonance imaging usually are unnecessary in
the evaluation of thyroid tumors except for large or retrosternal lesions and for
assessing suspected invasion into surrounding structures. MRI is more accurate than
. CT in distinguishing recurrent or persistent thyroid tumor from postoperative fibrosis
Thyroid Isotope Scanning
Scanning the thyroid with 123I or 99mTc can indicate the functional activity of a
nodule and of the thyroid and correlate the location of palpable nodules with the
nodules seen with scanning. Scanning with 131I has been largely replaced by 123I or
99mTc scans to lower the dose of radiation delivered to the thyroid gland during the
investigation. Nodules that trap less iodine than the surrounding thyroid tissue are
termed “cold,” nonfunctional, or hypofunctional (Fig. 36-21). Almost 85 percent of
nodules on scanning are cold, and these lesions have a 10 to 25 percent chance of
malignancy. Of the 5 percent of nodules shown to be “hot” on scanning,
approximately 1 percent are malignant. Thyroid scanning is recommended in the
assessment of thyroid nodules only in those patients who have follicular thyroid
. nodules on FNAC
Laboratory Findings
Thyroid function tests are not useful in the assessment of patients with thyroid
nodules, because most patients with thyroid cancer are euthyroid. In those patients
presenting with hyperthyroidism and a solitary nodule, the chances of the nodule's
being malignant are very low. Serum thyroglobulin levels cannot differentiate benign
from malignant thyroid nodules unless the levels are extremely high, in which case
metastatic thyroid cancer should be suspected. Thyroglobulin levels are useful in
following patients who have undergone total thyroidectomy for thyroid cancer,
excluding medullary thyroid cancer, and also for monitoring patients with nodules
being followed nonoperatively. Serum calcitonin levels should be obtained in patients
with a family history of medullary thyroid cancer or multiple endocrine neoplasia type
II (MEN II) and where FNAC demonstrates medullary thyroid cancer to be present.
Patients who are RET oncogene positive should always have a 24-h urine collection