Goiter, Thyroid Nodules, and Thyroid Carcinoma6'7

GENERAL PRINCIPLES

• The evaluation of goiter is based on palpation of the thyroid and evaluation of thyroid function. If the thyroid is enlarged, the examiner should determine whether the enlargement is diffuse or nodular.

• Thyroid scans and ultrasonography do not provide additional useful information about goiters that are diffuse by palpation and should not be performed in these patients. In contrast, all palpable thyroid nodules should be evaluated by ultrasonography.

• In rare patients, more commonly in those with MNG, the gland compresses the trachea or esophagus and causes dyspnea or dysphagia, necessitating treatment. Thyroxine treatment has little, if any, effect on the size of MNGs. Subtotal thyroidectomy is most commonly used to relieve compressive symptoms. RAI therapy will reduce gland size and relieve symptoms in most patients if surgery is not an option, though much higher doses are necessary if the patient is euthyroid.

• Diffuse goiter

î Almost all euthyroid diffuse goiters in the US are due to chronic lymphocytic thyroiditis (Hashimoto thyroiditis). This diagnosis can be confirmed by measurement of antithyroid peroxidase antibodies. Because Hashimoto thyroiditis may also cause hypothyroidism, plasma TSH should be measured.

î Diffuse euthyroid goiters are usually asymptomatic, and therapy is seldom required. Patients should be monitored regularly for the development of hypothyroidism.

î Diffuse hyperthyroid goiter is most commonly because of Graves disease, and treatment of the hyperthyroidism usually improves the goiter (see “Hyperthyroidism” section).

• Nodular goiter

î Between 30% and 50% of people have nonpalpable thyroid nodules that are detectable by ultrasound. These nodules rarely have any clinical importance, but their incidental discovery may lead to unnecessary diagnostic testing and treatment.

î Nodules are more common in older patients, especially women, and 5%-10% of thyroid nodules are thyroid carcinomas.

DIAGNOSIS

Clinical Presentation

HISTORY

Clinical findings that increase the risk of carcinoma include the presence of cervical lymphadenopathy, a history of radiation to the head or neck, and a family history of medullary thyroid carcinoma or multiple endocrine neoplasia syndromes type 2A or 2B.

PHYSICAL EXAMINATION

A hard, fixed nodule, recent nodule growth, or hoarseness due to vocal cord paralysis suggests malignancy.

Diagnostic Testing

• All patients with one or more palpable thyroid nodules on examination or thyroid nodules identified by other imaging modality should undergo a dedicated thyroid ultrasound as this is the most informative imaging for malignancy risk in thyroid nodules.

• Guidelines from the American Thyroid Association classify malignancy risk and biopsy recommendations based on nodule characteristics and size.

î Nodules are characterized into the following risk classes based on their ultrasound appearance: high suspicion (gt;70%-90% malignancy risk), intermediate suspicion (10%-20% malignancy risk), low suspicion (5%-10% malignancy risk), very low suspicion (lt;3% malignancy risk), and benign (lt;1% malignancy risk).

î High and intermediate suspicion nodules warrant evaluation by fine needle aspiration (FNA) when they are gt;1 cm. Low suspicion nodules should be evaluated at gt;1.5 cm and very low risk nodules at 2 cm. Benign nodules require no further follow-up.

î In a few patients, hyperthyroidism develops as a result of “toxic” nodules that overproduce thyroid hormone (see “Hyperthyroidism” section). These nodules can be identified with a radionuclide scan and do not require FNA evaluation as the malignancy risk is only 1%-2%.

TREATMENT

Patients with thyroid carcinoma or suspicion for thyroid carcinoma by FNA cytology typically initially undergo surgical resection with either hemi- or total thyroidectomy, sometimes followed by adjuvant therapy with RAI, and should be managed in consultation with an endocrinologist.

Follow-Up

• Further follow-up depends on FNA results. Benign nodules should undergo repeat ultrasound depending on initial ultrasound risk: high risk in 6-12 months and low intermediate in 12-24 months. The utility of following very low-risk nodules is unclear. Nodules with benign cytology should also be reevaluated periodically by palpation. Thyroxine therapy has little or no effect on the size of thyroid nodules and is not indicated.

• Nodules with nondiagnostic cytology because of insufficient sampling should undergo repeat biopsy.

• The management of thyroid nodules with indeterminate cytology is less clear. Nodules with atypia of undetermined significance or follicular lesion by cytology can be further evaluated with molecular diagnostic testing to estimate risk and guide surgical decision-making.