Imaging Analysis

Active surveillance of papillary thyroid microcarcinoma not for all patients

A 43-year-old Hispanic man was referred to the endocrine clinic after his primary care provider felt a thyroid nodule during an annual physical exam. His medical history was unremarkable. He reported no family history of thyroid disease, including thyroid cancer. He did not have a history of head and neck radiation. His thyroid function was normal with a thyroid-stimulating hormone level of 1.08 uIU/mL.

Imaging vs. biopsy

Stephanie L. Lee

Ultrasound imaging in the clinic showed multiple 1-cm hypoechoic nodules in both lobes of the thyroid gland. The most suspicious nodule was located in the posterior portion of the right mid-thyroid lobe. The nodule was highly suspicious by ultrasound criteria for malignancy with a hypoechoic echotexture with infiltrative margins, microcalcification and extrathyroidal extension (Figure).

Although routine biopsy of a thyroid nodule that measures 1 cm or less is not recommended, if a biopsy is performed and found to be malignant, surgical resection is recommended by the 2016 American Thyroid Association guideline. An alternative that is gaining in popularity is active surveillance with ultrasound exams every 6 months instead of surgery. Ultrasound can help categorize which thyroid microcarcinomas are at higher risk for tumor recurrence and nodal metastases.

Papillary thyroid microcarcinoma is defined as papillary thyroid carcinoma that measures 1 cm or less. These small cancers are commonly thought to be occult with nearly no risk for death and a low risk for nodal recurrence. However, large cancers must grow from a smaller tumor and, therefore, it is important to identify those tumors that will grow, invade, metastasize and result in death.

Figure. Sagittal ultrasound images of the right thyroid lobe. Two 1-cm hypoechoic nodules in the mid and lower poles of the thyroid. Both hypoechoic nodules have infiltrative margins (yellow arrows) and microcalcifications (white arrows). Extrathyroidal extension of the cancer is shown by the interruption of the thyroid capsule with extension of the mass beyond the thyroid margin (red line). (A) Sagittal image showing infiltrative margins and microcalcification. (B) Duplicate image with the posterior capsule of the thyroid outlined in red and extrathyroidal extension.

Images courtesy of Stephanie L. Lee, MD, PhD, ECNU reprinted with permission.

Recent studies have observed many patients with papillary microcarcinoma and found that, after 10 years, only 7% to 8% of the tumors grew by 3 mm or more, and only 1% to 3.8% developed nodal metastases. None of the patients developed distant metastases or died as a result. However, careful evaluation of these studies shows that the patients who were selected for observation were at particularly low risk (Table) without evidence of or increased risk for extrathyroidal invasion or nodal metastases.

Surveillance vs. surgery

Sugitani and colleagues proposed three categories of papillary thyroid microcarcinoma. Type I, the lowest-risk cancer, is intrathyroidal and asymptomatic. Conservative follow-up with ultrasonography every 6 or 12 months is recommended. Type II, the early stage of the usual low-risk papillary carcinoma, is treated by lobectomy after an increase in size is noted during conservative follow-up. Type III tumors are the clinically symptomatic papillary thyroid microcarcinomas with extrathyroidal invasion or metastases, representing a high-risk cancer that should be treated by total thyroidectomy with consideration for radioactive iodine therapy.

Studies are starting to identify the patients with type II papillary thyroid microcarcinoma that may require surgery because of growth or nodal metastases discovered during active surveillance. Progression has been observed in younger vs. older age (> 60 years), during pregnancy, and in those nodules with extensive microcalcification and extrathyroidal extension. Multifocality of the papillary microcarcinoma was not associated with an increased risk for tumor recurrence.

Active surveillance of papillary microcarcinoma is not yet standard of care in the United States. This may change since Sugitani and colleagues and Ito and Miyauchi independently have shown that properly selected patients with papillary microcarcinoma can undergo active surveillance rather than surgery. It is expected that during an observation period of 5 to 10 years, the microcarcinomas will increase in size in 5% to 10% of patients and 2% to 4% develop lymph node metastases. Of note, this risk for local metastases of these patients under active surveillance is similar to the risk of those patients with microcarcinomas who have had a thyroidectomy with or without radioactive iodine therapy.

Patient treatment

The patient presented here is not a good candidate for active surveillance because of the increased risk for tumor recurrence and nodal metastases predicted by the extrathyroidal extension of his cancer, his young age and the large number of microcalcifications present. He has been referred for a total thyroidectomy and central neck nodal dissection because of the macroscopic extrathyroidal extension of the tumor.

A 43-year-old Hispanic man was referred to the endocrine clinic after his primary care provider felt a thyroid nodule during an annual physical exam. His medical history was unremarkable. He reported no family history of thyroid disease, including thyroid cancer. He did not have a history of head and neck radiation. His thyroid function was normal with a thyroid-stimulating hormone level of 1.08 uIU/mL.

Imaging vs. biopsy

Stephanie L. Lee

Ultrasound imaging in the clinic showed multiple 1-cm hypoechoic nodules in both lobes of the thyroid gland. The most suspicious nodule was located in the posterior portion of the right mid-thyroid lobe. The nodule was highly suspicious by ultrasound criteria for malignancy with a hypoechoic echotexture with infiltrative margins, microcalcification and extrathyroidal extension (Figure).

Although routine biopsy of a thyroid nodule that measures 1 cm or less is not recommended, if a biopsy is performed and found to be malignant, surgical resection is recommended by the 2016 American Thyroid Association guideline. An alternative that is gaining in popularity is active surveillance with ultrasound exams every 6 months instead of surgery. Ultrasound can help categorize which thyroid microcarcinomas are at higher risk for tumor recurrence and nodal metastases.

Papillary thyroid microcarcinoma is defined as papillary thyroid carcinoma that measures 1 cm or less. These small cancers are commonly thought to be occult with nearly no risk for death and a low risk for nodal recurrence. However, large cancers must grow from a smaller tumor and, therefore, it is important to identify those tumors that will grow, invade, metastasize and result in death.

Figure. Sagittal ultrasound images of the right thyroid lobe. Two 1-cm hypoechoic nodules in the mid and lower poles of the thyroid. Both hypoechoic nodules have infiltrative margins (yellow arrows) and microcalcifications (white arrows). Extrathyroidal extension of the cancer is shown by the interruption of the thyroid capsule with extension of the mass beyond the thyroid margin (red line). (A) Sagittal image showing infiltrative margins and microcalcification. (B) Duplicate image with the posterior capsule of the thyroid outlined in red and extrathyroidal extension.

Images courtesy of Stephanie L. Lee, MD, PhD, ECNU reprinted with permission.

Recent studies have observed many patients with papillary microcarcinoma and found that, after 10 years, only 7% to 8% of the tumors grew by 3 mm or more, and only 1% to 3.8% developed nodal metastases. None of the patients developed distant metastases or died as a result. However, careful evaluation of these studies shows that the patients who were selected for observation were at particularly low risk (Table) without evidence of or increased risk for extrathyroidal invasion or nodal metastases.

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Surveillance vs. surgery

Sugitani and colleagues proposed three categories of papillary thyroid microcarcinoma. Type I, the lowest-risk cancer, is intrathyroidal and asymptomatic. Conservative follow-up with ultrasonography every 6 or 12 months is recommended. Type II, the early stage of the usual low-risk papillary carcinoma, is treated by lobectomy after an increase in size is noted during conservative follow-up. Type III tumors are the clinically symptomatic papillary thyroid microcarcinomas with extrathyroidal invasion or metastases, representing a high-risk cancer that should be treated by total thyroidectomy with consideration for radioactive iodine therapy.

Studies are starting to identify the patients with type II papillary thyroid microcarcinoma that may require surgery because of growth or nodal metastases discovered during active surveillance. Progression has been observed in younger vs. older age (> 60 years), during pregnancy, and in those nodules with extensive microcalcification and extrathyroidal extension. Multifocality of the papillary microcarcinoma was not associated with an increased risk for tumor recurrence.

Active surveillance of papillary microcarcinoma is not yet standard of care in the United States. This may change since Sugitani and colleagues and Ito and Miyauchi independently have shown that properly selected patients with papillary microcarcinoma can undergo active surveillance rather than surgery. It is expected that during an observation period of 5 to 10 years, the microcarcinomas will increase in size in 5% to 10% of patients and 2% to 4% develop lymph node metastases. Of note, this risk for local metastases of these patients under active surveillance is similar to the risk of those patients with microcarcinomas who have had a thyroidectomy with or without radioactive iodine therapy.

Patient treatment

The patient presented here is not a good candidate for active surveillance because of the increased risk for tumor recurrence and nodal metastases predicted by the extrathyroidal extension of his cancer, his young age and the large number of microcalcifications present. He has been referred for a total thyroidectomy and central neck nodal dissection because of the macroscopic extrathyroidal extension of the tumor.