Thyroid Ultrasonography—A Review

Overview of the management of differentiated thyroid cancer

Thyroid cancer is an uncommon tumor accounting for roughly 1% of all new malignancies. Differentiated (ie, papillary or follicular) thyroid carcinoma is usually asymptomatic, and frequently appears as a solitary thyroid nodule but few show cervical lymphadenopathy or metastasis to lung, bone, or liver. Fine needle aspiration (FNA) is recommended in the initial diagnostic test. Depending on the size of the lesion and other associated risk factors, most patients are treated with total or near total thyroidectomy. Postoperative radioiodine ablation is performed when tumor has a potential for recurrence. Recurrence rates and cancer-specific mortality is decreased by suppressing thyroid stimulating hormone (TSH). Long-term surveillance and follow-up with physical examination every 3 to 6 months for 2 years and then annually if patient remains cancer free. Whole body iodine scans are done every 12 months for follow-up until one negative scan (either withdrawal of thyroid hormone or rhodium complex -TSH). Thyroglobulin measurements (with antithyroglobulin antibodies) and ultrasound neck are suggested at 6 and 12 months and then annually if disease free.

Recombinant human thyrotropin stimulation of thyroglobulin in the follow-up of patients with stage I or II differentiated thyroid carcinoma

OBJECTIVE

To present an approach for follow-up of low-risk patients who have undergone treatment for differentiated thyroid carcinoma.

METHODS

We review our experience with monitoring of 167 patients who had undergone near-total thyroidectomy for stage I or II thyroid carcinoma and were receiving levothyroxine and discuss the advantages and disadvantages of various tests for detection of recurrent disease in this setting.

RESULTS

Almost 200,000 patients who have been treated for thyroid cancer live in the United States and require monitoring for possible recurrence of their disease. Most of these patients had stage I or II well-differentiated cancer. A cost-efficient method of follow-up for these low-risk patients is needed that relies on measurement of serum thyroglobulin (Tg) rather than expensive isotope imaging procedures. The availability of recombinant human thyrotropin (thyroid-stimulating hormone) (rhTSH) allows the evaluation of Tg dynamics and provides another method, along with ultrasonography, to monitor these patients. Among our 167 patients, 10 had Tg measurements of 2.5 to 5.0 ng/mL and were thought to be at risk for recurrent cancer. Ultrasonography of the neck revealed no suspicious lymph nodes. Tg response to rhTSH stimulation disclosed that two of these patients had an exaggerated increase in Tg level, compatible with persistent or recurrent cancer.

CONCLUSION

Although rhTSH stimulation testing has not yet become established in clinical practice, the finding of an exaggerated Tg response to rhTSH in patients with previously treated thyroid cancer seems to be an early indication of recurrent disease.

Role of ultrasonography in the diagnosis and management of thyroid cancer

OBJECTIVE

To review the role of ultrasonography in the detection and management of thyroid cancer.

METHODS

Viewpoints are presented on the appropriate applications and the advantages of ultrasonography, based on an extensive personal experience with more than 1,500 ultrasound examinations for assessment of thyroid nodules and for follow-up surveillance of patients with thyroid cancer.

RESULTS

Ultrasonography is ideal for thyroid imaging because of the high echogenicity of thyroid tissue, the superficial site of the thyroid that allows the use of high-frequency transducers yielding high resolution, and the low expense compared with other techniques. In patients with a thyroid nodule, ultrasonography can assist in distinguishing benign from malignant disease. Ultrasound studies will characterize the presence of cystic versus solid elements, the degree of echogenicity of solid elements, the existence of calcifications, and the regularity and definition of the nodule borders. Although individual sonographic features of thyroid nodules are not specific for benign or malignant lesions, a constellation of typical features has more diagnostic value. Hypoechogenicity, poorly defined irregular margins, and microcalcifications are characteristics that should increase the index of suspicion for a malignant nodule. Cytologic examination of fine-needle aspirates is the optimal diagnostic test, and ultrasonographic guidance for performance of the aspiration biopsy is often helpful and sometimes critical. Ultrasonography is also useful for detection of cervical lymph node metastatic lesions. Lymph nodes involved with metastatic thyroid cancer tend to become rounded and bulging, and they lose their hilar echoes as their structure becomes disrupted.

CONCLUSION

Because of its high resolution and relatively reasonable cost, ultrasonography is valuable in the diagnosis and management of thyroid cancer.