Surgical Treatment of Thyroid Nodules by Dr. Michael Dailey
Thyroid nodules are common. A nodule is palpable in 5% of the general population and visible on ultrasound in approximately 50%. When does a nodule warrant further investigation and treatment? Whenever considering management and workup of a nodule, risk factors for malignancy should be sought from the patient. That would include a history of radiation, nodule growth, hoarseness, dysphagia, and a family history of thyroid cancer or multiple endocrine neoplasia (MEN) syndromes. Other red flags include the extremes of age (younger than 20 or older than 70) and male gender, as these populations have a higher incidence of malignancy when a nodule is discovered.
A family history of medullary carcinoma of the thyroid should trigger genetic testing for the RET proto-oncogene. Incidentalomas (a tumor found by coincidence without any clinical symptoms or suspicion) among at-risk patients, those greater than 1 cm and palpable nodules should be evaluated further with ultrasound. Further work-up with ultrasound guided needle biopsy is indicated when the nodule is hypoechoic or mixed and greater than 1 cm or when there are features that have a strong correlation with malignancy. These concerning features include irregular margins, microcalcifications, increased vascularity, and extracapsular growth. Multinodular goiters have the same risk of cancer as a solitary nodule. Therefore, the nodules within a goiter that demonstrate any concerning sonographic findings should be biopsied as well.
Thyroid FNA (fine needle aspiration) has a sensitivity and specificity of 95% and is the test of choice to determine risk of malignancy. Typically, FNA results are grouped into one of the following four categories: benign, suspicious, malignant, or indeterminate. Benign nodules under 4 cm should be followed with ultrasound and biopsies should be repeated if significant growth is demonstrated. Nodules greater than 4 cm should be removed regardless of the FNA findings, as sampling error becomes a concern as the nodule size increases. Suspicious nodules may be further evaluated with a hemithyroidectomy, intraoperative frozen section, and total thyroidectomy, as indicated, if carcinoma is demonstrated.
The majority of patients who undergo hemithyroidectomy will maintain adequate thyroid function and will not require thyroid hormone replacement. Malignant lesions are typically removed with a total thyroidectomy. This recommendation is made based on the high incidence of multifocal carcinoma and for the purposes of postoperative radioactive iodine, which is most effective when the thyroid remnant is minimized. Other pathologic features found on FNA that raise concern for underlying malignancy, but are not diagnostic and are therefore “indeterminate,” include follicular neoplasm (15% risk of malignancy), Hurthle cells (14% risk of malignancy) and atypical cells (65% risks of malignancy).
Thyroidectomy is generally a safe and well-tolerated operation. Most patients who have a hemithyroidectomy can return home the same day, but patients who have a total thyroidectomy are typically monitored overnight due to the potential for hypocalcemia. Temporary hypocalcemia is expected to occur in 25 to 50% of patients undergoing total thyroidectomy, necessitating temporary calcium and Vitamin D supplementation.
Permanent hypoparathyroidism is much less common, seen in less than 1% of patients who undergo total thyroidectomy. Similarly, temporary recurrent laryngeal nerve injury occurs in approximately 10% of total thyroidectomy patients, whereas permanent recurrent laryngeal nerve injury occurs less than 1% of the time.
A recent advance in thyroidectomy is intraoperative nerve monitoring with electrodes imbedded in special endotracheal tubes. Multiple studies have not demonstrated a statistically significant reduction in nerve injuries utilizing this technology, but it can be helpful in identifying and preserving nerves that have an aberrant course.
Other advances have focused on “minimally invasive” techniques, primarily aimed at minimizing the neck scar seen in thyroidectomy. The typical thyroidectomy scar was approximately 10 cm. In most patients, this can be reduced to 4.5 cm and is set in a horizontal neck crease, which usually heals nicely. Endoscopic approaches to the thyroid with a smaller incision in the neck (2.5 cm), or incisions in the axilla with subcutaneous tunnels to the neck, have reduced neck scarring further. Trade-offs in scar aesthetics that are improved by endoscopic techniques must be balanced with potential increased time, expense, and additional personnel needed to perform these approaches, and therefore they have not been widely accepted.