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A therapeutic strategy for incidentally detected papillary microcarcinoma of the thyroid

Abstract

Papillary microcarcinoma of the thyroid (PMCT) is defined as papillary carcinoma measuring 1.0 cm or less. PCMT are frequently detected by ultrasonographic screening and ultrasonography-guided fine-needle aspiration biopsy. Although PMCT can pathologically show a high incidence of multifocality and lymph node metastasis in surgical specimens, most tumors grow slowly or not at all when they are monitored without surgery. In our observations only 6.7% of PMCT enlarged by 3.0 mm or more in diameter during 5 years of follow-up, and nodal metastases became detectable in 1.7% of patients overall. Observation without surgery could, therefore, be an attractive alternative for patients with low-risk PMCT; however, occult PMCT, which are diagnosed as the origin of lymph node or distant metastasis, show a worse prognosis. Even among incidentally detected PMCT, tumors with ultrasonographically detectable nodal metastasis are more likely to recur. Because such PMCT are most likely to recur in the regional lymph nodes, careful therapeutic neck dissection and total thyroidectomy are required. For incidentally detected and low-risk PMCT, careful observation without surgery might be acceptable, but careful and systematic surgery should be performed for patients with PMCT demonstrating aggressive characteristics.

Key Points

  • Papillary microcarcinoma is incidentally found in autopsy specimens and in otherwise healthy humans

  • Observation without surgery is an attractive alternative for patients with low-risk papillary microcarcinoma

  • Ultrasonography is a useful tool for detecting and monitoring papillary microcarcinoma

  • Careful surgical therapy is required for patients who have papillary microcarcinoma with high-risk factors, such as clinically apparent lymph node metastasis and massive extrathyroid extension

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Figure 1: Proportion of patients whose papillary microcarcinoma of the thyroid showed enlargement by 3.0 mm or more
Figure 2: A flow chart of our proposed therapeutic strategy for incidentally detected papillary microcarcinoma of the thyroid
Figure 3: A Kaplan–Meier curve showing disease-free survival of patients with papillary microcarcinoma of the thyroid in classes N0, N1a, or N1b stage who underwent modified radical neck dissection

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Correspondence to Akira Miyauchi.

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Ito, Y., Miyauchi, A. A therapeutic strategy for incidentally detected papillary microcarcinoma of the thyroid. Nat Rev Endocrinol 3, 240–248 (2007). https://doi.org/10.1038/ncpendmet0428

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