A 27-year-old primigravida at 8 weeks gestation is found to have a thyroid nodule during her initial prenatal visit. She has fatigue and frequent nausea with vomiting. The patient has no heat or cold intolerance and no skin changes. She has no dysphagia to solids or liquids, although she has been eating more carbohydrates since becoming pregnant. Medical history is otherwise not significant. The patient does not use tobacco, alcohol, or illicit drugs. Temperature is 36.7 C (98.1 F), blood pressure is 110/70 mm Hg, pulse is 86/min, and respirations are 18/min. Physical examination shows a small, 1.5-cm nodule in her right thyroid gland. Pelvic examination reveals a slightly enlarged uterus consistent with 8 weeks gestation. Serum TSH is normal. Ultrasound of her thyroid reveals a 1.5-cm hypoechoic nodule in her right thyroid lobe with irregular margins, internal microcalcifications, and internal vascularity. Which of the following is the next most appropriate step in management of this patient?
Thyroid nodules are common and may be diagnosed on physical examination or noted incidentally when imaging studies are obtained for other reasons. Once a thyroid nodule is found, cancer risk factors (eg, family history, radiation exposure) should be assessed by history. Physical examination should evaluate the approximate size, mobility, and firmness of the thyroid nodule and whether enlarged cervical lymph nodes are present. A serum TSH should be obtained.
If serum TSH is normal, a thyroid ultrasound is the next step to determine nodule sonographic features and size. Certain sonographic features (eg, microcalcifications, irregular margins, internal vascularity) carry a much higher risk of malignancy than others (eg, cystic or spongiform lesions). Thyroid nodules >1 cm with these high-risk sonographic features should undergo fine-needle aspiration (FNA) biopsy. Thyroid nodules >2 cm should all undergo FNA (unless they are cystic, as they have a low risk of malignancy).
Pregnant women undergo the same evaluation but should not receive radioactive iodine (for either diagnosis or treatment) because it can lead to congenital hypothyroidism, intellectual disability, and increased risk of malignancy in the fetus. In this patient who has a >1-cm nodule with high-risk sonographic features, workup should proceed with an FNA, which is safe during pregnancy.
(Choice B) Thyroid nodules may be found incidentally on an MRI scan; however, ultrasound is the initial imaging modality of choice for workup of thyroid nodules.
(Choice C) Radionuclide scans may be done for thyroid nodules in the setting of a low TSH (hyperthyroid) level because those nodules are often hot and less likely to be cancerous. In this patient with a normal TSH, an FNA is the appropriate next step. In addition, radioactive iodine should never be used in pregnancy because of the risk to the fetus.
(Choices D and F) If a thyroidectomy is needed (eg, due to cancer), it can often be delayed until after delivery. However, should the workup reveal a more aggressive or rapidly growing thyroid cancer, the optimal timing of surgery would be during the second trimester. Therefore, this patient should undergo an FNA to determine if (and when) a thyroidectomy is needed.
(Choice E) Thyroglobulin is produced by both normal thyroid tissue and differentiated thyroid cancer cells. Therefore, it is a useful tumor marker to monitor for recurrence after the thyroid gland has been completely removed.
Educational objective:
Thyroid nodules that have suspicious sonographic features should undergo fine-needle aspiration biopsy, even if the patient is pregnant.