THYROID NODULE

dr. Kunta Setiaji, Sp.B(K)Onk

Overview

Enlargement in the thyroid gland have been collectively reffered to as goiters

Goiters may be diffuse or focal and may be either smooth or noduler

They may be associated with normal thyroid function or with thyroid hyperfunction or hypofunction

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 neoplasm

DIFFUSE THYROID ENLARGEMENTS

A. Colloid and iodine-deficiency goitersClinical presentation. These are large, bulky, soft enlargements of the thyroid, which may grow to sizable proportions. They occasionally produce compressive symptoms.Treatmenta. Compressive symptoms may require surgery, but more often than not they are removed for cosmetic reasonb. Other treatment is medical and depends on the cause of the goiter.

DIFFUSE THYROID ENLARGEMENTS

B. ThyroiditisInflammations of the thyroid can be acute, subacute, or chronic

1. Acute thyroiditis is an uncommon disorder caused by the hematogenous spread of microorganisms into the thyroid gland.Clinical presentationThe clinical picture is that of acute inflammation with pain and tenderness, swelling, and redness over one or both lobes.The condition may occur in immuno-compromised 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.

2. 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 presentationIt 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 the release of thyroid hormone from the gland secondary to the inflammation, but the radioiodine uptake is always decreased, distinguishing it from Grave’s disease.The disorder is self-limited, usually lasting from 2-6 months.Occasonally, subacute thyroiditis is painless, causing hyperthyroidism without symptoms of inflammation in the gland, so that it may resemble Grave’s disease clinically. This form is also distinguished from Grave’s disease by the low radioiodine uptake. Painless thyroiditis not infrequently occurs during the post partum period.

Treatment.Symptoms are controlled with either aspirin or corticosteroids.Beta-adrenergic blockade may be used to relieve the symptom of hyperthyroidism.Antithyroid drugs are ineffective, since the hyperthyroidism is not caused by increased thyroid hormone synthesis.

3. Chronic Thyroiditisoccurs in two majors forms, Hashimoto’s and Riedel’s.

a. Hashimoto’s thyroiditis (Struma Lymphomatosa) is a relatively common autoimmune disorder that occurs predominantly in women. It is considered to be autoimmune since it coexist with other autoimmune conditions and is associated with the presence of antithyroid antibodies in the serum.Clinical presentation.It should be considered in any woman who has a goiter and hypothyroidism. The enlargement in the thyroid is most commonly diffuse and less commonly nodular or asymmetrical. There does not appear to be predilection for thyroid cancer, but thyroid cancer should be suspected when the thyroiditis is associated whit one or more nodules.Diagnosis. Thyroid function studies are usually normal. Radioiodine uptake and scans show decreased uptake with patchy distribution.Treatment. This form of thyroiditis is ussually treated with long-term thyroxine therapy. The gland will usually regress in size unless there is considerable fibrosis. Surgery is indicated when a dominant mass is not suppressed by thyroxine therapy; when the gland continous to enlarge despite thyroxine therapy; and when the history and physical findings or the needle biopsy are suggestive of thyroid malignancy.

b. Riedels (fibrosis thyroiditis) is a relatively rare form of thyroiditis in which the thyroid parenchyma is almost completely replaced with dense fibrous tissue.Clinical presentation. Usually occurs in middle age and may cause pressure symptom, such as cough, dyspnea, or dysphagia. Because the gland is ussually stony hard, the condition is difficult to distinguish from thyroid malignancy.Treatment. Surgery, namely resection of the isthmus, is needed both to confirm the diagnosis and to relieve the symptoms.

NODULAR THYROID ENLARGEMENT

Clinical presentation. These goiters are caused by adenomatous hyperplasia of the thyroid gland.The thyroid enlargement is thought to be due to long standing stimulation of the thyroid by TSH during a period of suboptimal thyroid hormone production.The progression to multinodularity occurs through a process of cyclic changes of hyperplasia and colloid formation.Despite the relatively high incidence of adenomatous hyperplasia, the presence of biologically active thyroid cancer in multinodular goiters without clinical evidence of malignancy occurs in fewer than 1% of cases.

Pathogenesis.The nodules in the glands show a wide variety of pathologic findings.Some are filled with colloid, while others show evidence of cystic degeneration. There may be focal calcification, hemorrhage, or scarring

Diagnosis.Most patients are asymptomatic, and the nodularityis detected on routine physical examination.Occasionally, attention may be drawn to the nodules because of pain, difficulty in swallowing, or dyspnea if the nodules enlarge either spontaneously or due to hemorrhage.Thyroid function studies are normal, as are the thyroid antibodies. Radioiodine uptake is normal but scanning shows variegated uptake of the radioiodine in the areas of multinodularity.

Treatment.If there are no clinical signs of malignancy and the gland is not symptomatic, no treatment is necessary, and simple observation is appropriate.If the gland is cosmetically objectionable or if pressure symptoms develop, then exogenous thyroid hormone should be given. The purpose of thyroxine therapy is to suppress endogenous TSH stimulation of the gland and allow the gland to shrink. Lifelong suppresive therapy with thyroxine should be given to minimize recurence.Subtotal thyroidectomy is advisable if the glands are large enough to produce compressive symptoms and do not regress with thyroxine therapy.If patients develop clinical signs of malignancy, this should be confirmed by needle aspiration biopsy, and appropriate surgery should be performed.

THYROID NEOPLASMOverview. The commonest reason for thyroid surgery

today is to diagnose or treat a suspected thyroid neoplasm that can not be diagnosed by conventionals means. Not infrequently, 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.

Assesment of thyroid nodules.a. Patient’s ageIn children, 50% of thyroid nodules are malignant.During the childbearing years, most nodules are benign.The incidence of cancer in nodules increases by about 10% a decade after age 40 years.b. Patient’s sex.Thyroid cancer is commoner in women than in menBenign thyroid nodules are also commoner in womenThe likelihood that a nodule will prove to be malignant is greater in men than in women.

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

d. History of radiation exposure.Exposure of the head and neck region to therapeutic x-rays has been found to increase the incidence of thyroid cancer 5 to 10 fold. Radiation has been given for a variety of disorders, such as an enlarged thymus in infancy, enlarged tonsils and adenoids during childhood, congenital hemangiomas of the head and neck region, acne vulgaris, and Hodgkin’s disease.

e. Characteristics of the nodule.Consistency. Nodules that are firm in consistency suggest malignancy; However, malignant nodules may undergo cystic degeneration so that they may be somewhat soft to palpation. Soft nodules are likely to be benign; however, long-standing adenomatous hyperplasi may be associated with calcification in the nodule.Infiltration of the nodule into the surrounding thyroid or overlying structures, such as the strap muscles or trachea, suggest 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. Growth patterns.Nodules that suddenly appear or increase in size should be suspected of being thyroid neoplasms. Hemorrhage into a preexisting 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 suggest 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 thyroid nodule is almost always diagnostic of a thyroid malignancy that has infiltrated the reccurent laryngeal nerve.Since 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 postopeartively if voice abnormalities occur.

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

Antithyroid antibodies may be elevated 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 be elevated in patients with medullary carcinoma of the thyroid.

Radioisotope scanning of the thyroid may be done with radioiodine or with Technetium-99m pertechnetate.Isotope tracers are taken up by normally functioning thyroid tissue, which appears as a “hot” area on thyroid scan; nodules that do not take up the tracers appear as “cold” areas.Approximately 20% of cold nodules will be malignant, and approximately 40% of thyroid cancer will take up the radioisotope tracer to some degree.

DIAGNOSTIC STUDIES

Ultrasonography.

Using an ultrasound probe, an image of of the size and shape of the thyroid gland and the nodules that is contains can be mapped. Thyroid nodules, thus, can be identified as either cystic, solid or complex.

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

Needle biopsy of the thyroid is designed to obtain cells for histopathologic or cytopathologic examination as an aid the diagnosis of thyroid nodules and the planning of therapy.

OPERATIVE APPROACH TO THE THYROID NODULE

Operative removal is the mainstay of treatment for thyroid carcinoma

The extent of the operation will depend upon the : Type of thyroid cancer; Extent of the tumor as determined from the preoperative findings. For a solitary nodule confined to one lobe, the minimal operation is total removal of that lobe and the isthmus and removal of the anterior portion of the opposite lobe.Biologic aggressiveness of the tumor.

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

The parathyroid glands and the reccurent laryngeal nerve should be identified in all operations.

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