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Diffuse non -nodular goiters with normal or decreased function are due to benign causes.

Focal or nodular goiters with normal function may be due to thyroid neoplasms. P.318

Diffuse thyroid enlargements

Colloid and iodine -deficiency goiters

Incidence. They occur infrequently in the United States.

Clinical presentation. These are large, bulky, soft enlargements of the thyroid that may grow to sizable proportions. They occasionally produce compressive symptoms.

Treatment

Compressive symptoms may require surgery, but occasionally they are removed for cosmetic reasons.

Other treatment is medical and depends on the cause of the goiter.

Thyroiditis. Inflammations of the thyroid can be acute, subacute, or chronic.

Acute suppurative thyroiditis is an uncommon disorder caused by the hematogenous spread of microorganisms into the thyroid gland.

Clinical presentation

The clinical picture is that of acute inflammation with pain and tenderness, swelling, and redness over one or both lobes.

The condition may occur in an immunocompromised patient.

Staphylococci and streptococci have been incriminated, but any organism can be causative.

Diagnosis is established by needle aspiration with appropriate bacteriologic studies.

Treatment is by open drainage or localized resection with administration of appropriate antibiotics.

Subacute thyroiditis (giant cell, granulomatous, or de Quervain's thyroiditis) is thought to be viral in origin and is often preceded by an upper respiratory infection.

Clinical presentation

It is characterized by sore throat, enlargement of the gland (which may be asymmetrical), and tenderness and induration over the gland.

Patients may have symptoms of hyperthyroidism due to the release of thyroid hormone from the gland secondary to the inflammation, but the radioiodine uptake is always decreased, distinguishing it from Graves' disease.

The disorder is self-limited, usually lasting from 2–6 months.

Occasionally, subacute thyroiditis is painless, causing hyperthyroidism without symptoms of inflammation in the gland, so it may resemble Graves' disease clinically. This form is also distinguished from Graves' disease by the low radioiodine uptake. Painless thyroiditis frequently occurs during the postpartum period.

Treatment. Symptoms are controlled with either aspirin or corticosteroids.

β-adrenergic blockade may be used to relieve the symptoms of hyperthyroidism.

Antithyroid drugs are ineffective because the hyperthyroidism is not caused by increased thyroid hormone synthesis.

Chronic thyroiditis occurs in two major forms, Hashimoto's and Riedel's.

Hashimoto's thyroiditis (struma lymphomatosa) is a relatively common autoimmune disorder that occurs predominantly in women. It is considered to be autoimmune because it coexists with other autoimmune conditions and is associated with the presence of antithyroid antibodies in the serum.

Clinical presentation. Because Hashimoto's thyroiditis is a rather common form of thyroid enlargement today, it should be considered in any woman who has a goiter and hypothyroidism. It is usually unassociated with any other symptoms. The enlargement in the thyroid is most commonly diffuse and is less commonly nodular or asymmetrical. There does not appear to be a predilection for thyroid cancer, but thyroid cancer should be suspected when the thyroiditis is associated with a dominant nodule. Needle biopsy is helpful in confirming the diagnosis.

Diagnosis. Thyroid function studies are normal or indicate hypothyroidism. Radioiodine uptake and scans show decreased uptake with patchy distribution.

Treatment. This form of thyroiditis is usually treated with long-term thyroxine therapy. The gland will usually regress in size unless there is considerable fibrosis.

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Surgery is indicated when a dominant mass is not suppressed by thyroxine therapy, when the gland continues to enlarge despite thyroxine therapy, and when the history and physical findings or the needle biopsy are suggestive of thyroid malignancy.

Riedel's (fibrous) thyroiditis is a relatively rare form of thyroiditis in which the thyroid parenchyma is almost completely replaced with dense fibrous tissue.

Clinical presentation. Riedel's thyroiditis usually occurs during middle age and may cause pressure symptoms, such as cough, dyspnea, or dysphagia. Because the gland is usually stony hard, the condition is difficult to distinguish from thyroid malignancy.

Treatment. Surgery (i.e., resection of the isthmus) is needed both to confirm the diagnosis and to relieve compression symptoms.

Overview. The most common reason for thyroid surgery today is to diagnose or treat a suspected thyroid neoplasm that cannot be diagnosed by other means. Frequently, a solitary or prominent thyroid nodule is detected on physical examination in an asymptomatic patient. The concern is that the nodule will be malignant, although most solitary thyroid nodules are benign. Clinical pathologic classification of primary thyroid malignancies is shown in Table 16 -1.

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TABLE 16-1 Clinical Pathologic Classification of Primary Thyroid Malignant Lesions

*Associated foci of anaplastic carcinoma convert this to virulence of anaplastic variety. (Reprinted with permission from Block MA, Cerny JC. Endocrine system. In: Beahrs OH, Beart RW Jr, eds. General Surgery—Therapy Update Service. Harwal Medical Publications: Media, PA; 1984:2–7.)

Assessment of thyroid nodules

Patient's age

In children, 10%–15% of thyroid nodules are malignant.

During the childbearing years, most nodules are benign.

The incidence of cancer in nodules increases by about 10% per decade after age 40 years.

Patient's sex

Thyroid cancer is more common in women than in men.

Benign thyroid nodules are also more common in women.

The likelihood that a nodule will prove to be malignant is greater in men than in women.

Family history of thyroid malignancy. Medullary carcinoma of the thyroid may be transmitted as an autosomal dominant trait, but other thyroid cancers are not transmitted genetically.

History of radiation exposure

Exposure of the head or neck region to therapeutic radiation has been found to increase the incidence of thyroid cancer 5- to 10 -fold.

The radiation exposure required to induce neoplasia may be as low as 50 rad.

Radiation was previously given for a variety of disorders, such as an enlarged thymus in infancy, enlarged tonsils and adenoids during childhood, congenital hemangiomas of the head or neck region, acne vulgaris, and Hodgkin's disease.

Thyroid cancers from radiation exposure are no different from those that occur without a history of radiation, but the latent interval from the time of radiation exposure until the development of thyroid cancer varies with the age at which the radiation exposure occurred.

When the thyroid is irradiated during infancy, the mean interval until development of thyroid cancer is 10–12 years.

When the thyroid is irradiated during adolescence, the mean interval until development of thyroid cancer is 20–25 years.

When the thyroid is irradiated during adulthood, the mean interval until development of thyroid cancer is 30 years.

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Characteristics of the nodule

Consistency

Nodules that are firm in consistency suggest malignancy; however, malignant nodules may undergo cystic degeneration, so they may be somewhat soft to palpation.

Soft nodules are likely to be benign; however, long-standing adenomatous hyperplasia may be associated with calcification in the nodule, making it firm.

Infiltration of the nodule into the surrounding thyroid or overlying structures, such as the strap muscles or trachea, suggests malignancy. However, malignant nodules may have no sign of infiltration and may mimic benign nodules.

Nodulation. Solitary nodules have a 20% chance of being malignant. Multiple nodules are present in as many as 40% of proven cases of thyroid malignancy.

Growth patterns. Nodules that suddenly appear or suddenly increase in size should be suspected of being thyroid neoplasms. Hemorrhage into a pre -existing nodule, such as adenomatous hyperplasia, can cause a sudden increase in the size of the nodule, but this is frequently associated with pain.

Ipsilateral lymph node enlargement suggests thyroid malignancy. In children, as many as 50% of thyroid cancers are first detected because of cervical lymph node enlargement.

Mobility of the vocal cords should be assessed preoperatively in all patients undergoing thyroid operations.

Ipsilateral vocal cord paralysis in a patient with a thyroid nodule is almost always diagnostic of a thyroid malignancy that has infiltrated the recurrent laryngeal nerve.

Because vocal cord paralysis may not be associated with voice changes, the cords should be examined by either indirect or direct laryngoscopy or by nasal pharyngoscopy.

Examination should be repeated postoperatively if voice abnormalities occur.

Diagnostic studies. Although clinical evaluation is the mainstay in distinguishing benign from malignant thyroid nodules, alone it may be insufficient, and other diagnostic studies may be needed.

Thyroid function tests are of little value in diagnosing thyroid cancer. Nearly all thyroid cancers are nonfunctioning, as are the nodules of adenomatous hyperplasia. Therefore, fewer than 1% of all thyroid malignancies will be associated with hyperfunction.

Antithyroid antibody levels may be increased in patients with Hashimoto's thyroiditis, but thyroid cancer may coexist with thyroiditis; thus, a positive antibody test does not preclude the diagnosis of thyroid cancer.

Thyrocalcitonin assay will show an increased level in patients who have medullary carcinoma of the thyroid. Patients who are diagnosed with medullary carcinoma should undergo genetic testing for abnormalities of the RET proto -oncogene as well. Their family members may require genetic testing and counseling as well.

Radioisotope scanning of the thyroid may be done with radioiodine or with technetium-99m (99m Tc) pertechnetate.

Isotope tracers are taken up by normally functioning thyroid tissue, which appears as a “hot” area on a thyroid scan; nodules that do not take up the tracers appear as “cold” areas.

Approximately 20% of cold nodules will be neoplastic, and approximately 40% of thyroid cancers will take up the radioisotope tracer to some degree.

Radioisotope scanning may exclude nodules that are not malignant if they appear hot but does not discriminate benign cold nodules from malignant ones.

Iodine-123 (123 I) and -125 (125 I) give less radiation exposure than iodine -131 (131 I) because

they have shorter half -lives than 131 I. They do not provide any better discrimination than 131 I between benign and malignant thyroid nodules.

99m Tc pertechnetate is trapped in but, in contrast to radioiodine, not organified by the thyroid gland.

Nodules that are cold to radioiodine will also be cold to 99m Tc.

Tumors of the thyroid may take up 99m Tc and appear hot on the scan due to the

vascularity of the tumor. Thus, all nodules that are hot on a 99m Tc scan should be scanned with radioiodine to determine their function.

99m Tc delivers only a fraction of the radiation that is delivered by 131 I. It does not discriminate any better than does 131 I between benign and malignant thyroid nodules.

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Ultrasonography

Using an ultrasound probe, an image of the size and shape of the thyroid gland and the nodules that it contains can be mapped. Thus, thyroid nodules, can be identified as cystic, solid, or complex (i.e., a mixture of solid and cystic components).

Although ultrasonography can distinguish pure cysts of the thyroid, which are rarely malignant, from complex or solid masses, it cannot be used to absolutely distinguish benign from malignant complex or solid masses.

Features that may be suggestive of malignancy include the presence of micro - or macrocalcifications, solid echo -texture, appearance different from other nodules in the gland, indistinct borders, local invasion, or increased vascularity.

Ultrasonography is helpful in identifying thyroid nodules that are not clinically palpable and in directing a needle to a nonpalpable nodule for biopsy.

Needle biopsy of the thyroid allows for the histopathologic or cytopathologic examination of cells as an aid in the diagnosis of thyroid nodules and in planning therapy. Needle biopsy is the most useful diagnostic tool, aside from surgery, for distinguishing benign from malignant thyroid nodules.

However, none of these biopsy techniques can distinguish benign from malignant follicular neoplasms.

Fine-needle aspiration

Cells are aspirated from the nodule by applying suction to a syringe attached to a 21 - to 25 -gauge needle.

This technique obtains a specimen for cytopathologic examination of individual cells and clusters of cells.

The technique requires interpretation by a well-trained thyroid cytopathologist.

It has a good degree of accuracy and specificity in diagnosing thyroid malignant lesions

and, due to the small size of the needle, is associated with virtually no complications.

Inadequate or nondiagnostic specimens must be repeated. Otherwise, operative excision of the nodule may be required to establish the diagnosis.

Large-needle biopsy

A plug of tissue is aspirated from the nodule by applying suction to a syringe attached to an 18 - or 20 -gauge needle that is inserted into the nodule. Fragments of tissue are obtained for cytopathologic and histopathologic examination.

This technique offers some of the advantages as core biopsy but has a lower rate of complications as compared with core biopsy due to the smaller size of the needle.

The combination of fine -needle and large-needle aspiration carries with it an adequacy in diagnosis of 90%–95% in experienced hands.

Core biopsy

Using a 14 - or 18 -gauge specially designed needle (Tru-Cut), this biopsy technique obtains a cylinder of tissue from the thyroid nodule. The specimen is then fixed and stained for histopathologic analysis.

It is the most accurate method of assessing the histologic nature of a thyroid nodule.

Because of the large size of the needle, it is unsuitable for biopsy of small nodules.

Due to a relatively high incidence of bleeding complications, the technique is rarely performed.

Operative approach to the thyroid nodule (Fig. 16 -3)

Overview. Operative removal is the mainstay of treatment for thyroid carcinoma.

The extent of the operation will depend on the:

Histologic type of thyroid cancer

Extent of the tumor as determined from the preoperative assessment and the operative findings. For a solitary nodule confined to one lobe, the minimal operation is total removal of that lobe and the isthmus.

Biologic aggressiveness of the tumor

A frozen section of the resected tissue must always be obtained to determine whether the nodule is benign or malignant.

If the lesion is grossly benign in appearance and the frozen section reports a benign lesion, but the permanent sections reveal it to be papillary or follicular carcinoma,

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the extent of further surgery is determined by the biologic aggressiveness of the lesion.

FIGURE 16-3 Algorithm for evaluation and management of an asymptomatic thyroid nodule discovered on routine physical examination.

If the lesion appears to be grossly malignant and is confined to one lobe without invasion of surrounding tissues, then total removal of that lobe and the isthmus, and near -total removal of the opposite lobe are appropriate therapy.

If the lesion appears grossly malignant and extends beyond the thyroid or involves both lobes, then total thyroidectomy is indicated.

Lymph node resection is indicated when nodes appear to be grossly involved.

The resection should generally concentrate on nodes in the interjugular location, especially in the tracheoesophageal groove.

Prophylactic removal of uninvolved lymph nodes is of no proven benefit.

The parathyroid glands and the recurrent laryngeal nerve should be identified in all operations. The parathyroid glands should be reimplanted in an appropriate skeletal muscle site if their blood supply is compromised during thyroidectomy.

The complication rate after total thyroidectomy, and especially the incidence of permanent hypoparathyroidism, is significantly greater than the rate after near -total thyroidectomy. Therefore, total thyroidectomy should not be performed unless it is of proven clinical benefit.