This article is more than 5 years old. Information may no longer be current.
A 52-year-old woman with a history of hypothyroidism, left thyroid
Click Here to Manage Email Alerts
A 52-year-old woman with a history of hypothyroidism and a left thyroid nodule presents to the endocrine clinic for follow-up. She was initially referred 7 years prior for goiter on physical exam.
Her thyroid ultrasound revealed a heterogeneous, hypoechoic and hypervascular thyroid gland (Figure 1) with an 8-mm hyperechoic left mid-lobe nodule (Figures 2A and 2B). Biopsy was not performed because the nodule was less than 1 cm, as recommended by the American Thyroid Association guideline for nodules and cancer. She has been taking levothyroxine 50 mcg by mouth daily for the last 2 years with a normal thyroid-stimulating hormone level.
Today, she has no complaints and relates no trouble swallowing, change in neck size or change in voice. Thyroid ultrasound in the endocrine clinic showed diffusely enlarged gland parenchyma with a heterogeneous echotexture, hyperechoic lines and increased vascular flow (Figures 1A, B). In addition, the left nodule had increased in size to 1.4 cm × 1.1 cm × 1.2 cm and a new right nodule was identified measuring 0.9 cm × 0.8 cm × 0.5 cm. Both nodules were solid, hyperechoic compared with the rest of the hypoechoic parenchyma, with well-defined margins with scant intranodular and peripheral vascularity. A decision was made whether to biopsy the enlarging left thyroid nodule.
 Stephanie L. Lee |
 Matthew Spitzer |
Ultrasound typical of Hashimoto’s thyroiditis includes coarsened, heterogeneous, hypoechoic parenchyma with a micronodular pattern and hyperechoic lines or septations suggestive of fibrosis (Figure 1A). The decreased echogenicity is a result of lymphocytic infiltration, whereas the hyperechoic lines are bands of fibrosis that run through the parenchyma, typical of the pathology of Hashimoto’s thyroiditis. In addition, tiny hypoechoic micronodules measuring 1 mm to 7 mm are characteristic of thyroiditis with a positive predictive value for Hashimoto’s thyroiditis of 95%. It is thought that these tiny nodules are also hypoechoic due to deposits of lymphocytes with an echogenic rim due to the fibrous strands throughout the parenchyma (Figure 1A).
On color Doppler, the thyroid can vary from slightly hypervascular to markedly hypervascular (Figure 1B). Besides the diffuse form of Hashimoto’s thyroiditis, discrete nodules within the diffusely abnormal parenchyma may occur. Although this is a focal thyroiditis within a sonographically normal thyroid, it is unusual and represents about 5% of thyroid nodules. This patient had solid hyperechoic nodules in the background of the hypoechoic parenchyma of chronic thyroiditis. These nodules have the appearance of “white knight” nodules in a black background. These nodules are generally benign with a very low risk for malignancy.
|
Figures reprinted with permission from: Stephanie L. Lee, MD, PhD
|
|
|
A large multicenter study demonstrated that only 11% of nodules in glands with diffuse hypoechoic changes of chronic thyroiditis were solid and hyperechoic. Bonavita and colleagues characterized the sonographic patterns of 500 benign and malignant thyroid nodules. One of the 10 morphologic patterns was the white knight pattern described as a uniformly hyperechoic nodule in a hypoechoic background typical of Hashimoto’s thyroiditis. It is critical that the hyperechoic nodule have well-defined borders, no vascularity or be isovascular with the rest of the thyroid parenchyma and no calcification. Cytology of 17 white knight nodules in the report were benign colloid nodules or Hashimoto’s thyroiditis.
In a 2011 retrospective study of 811 nodules, researchers reported that the white knight nodules had 100% specificity for absence of malignancy. In 2010, a large multicenter study of nodules in Hashimoto’s thyroiditis also found that none of the solid and hyperechoic nodules in Hashimoto’s thyroiditis contained cancer. These studies support the concept that it is not necessary to biopsy white knight nodules.
The 2009, revised ATA guidelines did not address this specific type of white knight nodule, but these data are only recently published. With our patient, we discussed the very low risk for malignancy of her thyroid nodules noted on ultrasound and recommended against biopsy in favor of watchful waiting. TSH was 1.8 mcIU/mL, and she continues to take levothyroxine 50 mcg by mouth daily. She will return in 12 months for a repeat thyroid ultrasound exam.
Stephanie L. Lee, MD, PhD, is associate professor of medicine; associate chief, section of endocrinology, diabetes and nutrition; and associate professor of medicine at the Boston Medical Center.
Matthew Spitzer, MD, is a fellow in endocrinology, section of endocrinology, diabetes and nutrition, at Boston Medical Center.
For more information:
- Anderson L. AJR Am J Roentgenol. 2010;195:216-222.
- Bonavita JA. AJR Am J Roentgenol. 2009;193:207-213.
- Cooper DS. Thyroid. 2009;19:1167-1214.
- Virmani V. AJR Am J Roentgenol. 2011;196:891-895.
Disclosure: Drs. Spitzer and Lee report no relevant financial disclosures.