Thyroid and Parathyroid

Most thyroid nodules are benign and are colloid nodules or adenomas. To distinguish
between suspicious thyroid nodules that may be malignant and benign thyroid
. nodules, certain issues should be considered
Because 40 percent of patients with a solitary nodule or multiple thyroid nodules with
a history of previous head and neck irradiation will have cancer of the thyroid gland, a
history of external radiation to the head or neck is important. The age and gender of
the patient are also important. Thyroid nodules in children and elderly patients are
more likely to be malignant. Solitary nodules also are more common in men over 40
and women over 50 years of age. Signs that should prompt concern are rapid
enlargement of an old or new thyroid nodule, symptoms of local invasion (e.g.,
unilateral vocal cord paralysis), or compressive symptoms (e.g., dysphagia and
.( dyspnea from invasion into the trachea and esophagus
Approximately 15 percent of solitary thyroid nodules are malignant, and in hard
solitary thyroid nodules the risk of malignancy is two or three times higher. When the
apparently solitary nodule is found to be a dominant nodule in a multinodular thyroid
gland, the incidence of thyroid cancer in this nodule is less than 5 percent. An
exception to this is a history of previous head and neck irradiation or a history of
familial thyroid cancer. Lesions that are hard, gritty, or fixed to surrounding structures
such as the trachea or strap muscles are probably malignant. The presence of palpable
cervical lymphadenopathy adjacent to a thyroid nodule should be suspected as a
carcinoma. Cervical lymphadenopathy because of metastatic thyroid cancer may be
present when no thyroid nodule is palpable. These patients almost always have a
thyroid cancer that usually is present in the ipsilateral thyroid lobe. This cancer may
. be microscopic and demonstrated only after careful sectioning of the thyroid gland
Investigations
Fine-Needle Aspiration Cytology
The procedure of choice in evaluating thyroid nodules is fine-needle aspiration
cytology (FNAC). The test is fast, is minimally invasive, has few risks, causes little
discomfort to the patient, and has been shown to be specific and sensitive. It has
replaced radionuclide and ultrasonographic imaging in the preoperative evaluation of
. thyroid nodules
Ninety percent of nodules can be categorized into the following groups: benign, 65
percent; suspicious, 15 percent; malignant, 5 percent; and nondiagnostic, 15 percent.
The incidence of false-positive results is about 1 percent, and false-negative results,
. about 5 percent
FNAC is the investigation of choice in patients with thyroid nodules, but it has
limitations. The proportion of patients with suspicious cytology results ranges from 11
to 20 percent. Most have follicular or Hürthle cell neoplasms, and 20 percent of these
patients have a thyroid malignancy. There is no accurate method of predicting which
of these patients has a thyroid cancer, because the diagnosis depends on
demonstrating capsular or vascular invasion, which is not possible on FNAC. The
technique also is less reliable in patients who have previous irradiation to the head and
neck or have a family history of thyroid cancer, as many of these patients have
.
multifocal lesions