Thyroid papillary micro-carcinoma is defined as an isolated cancer with diameter no larger then 1.0 cm. It is considered to have good long-term prognosis. Analyses reveal that these small cancers could be more aggressive than expected. Authors also find that cancer volume, rather than diameter, expansion is the best structural tool in identifying tumors at risk of progression.
J C E M
Context: Papillary thyroid micro-carcinoma (PTMC) usually has an excellent prognosis.
Objective: To evaluate the three-dimensional structures of PTMCs, using serial neck ultrasonography (US) in patients under active surveillance.
Design and Setting: A retrospective cohort study.
Participants: In total, 192 patients diagnosed with PTMC under active surveillance for >1 year were included in a median 30-month follow-up. Changes in tumor size were evaluated not only using the maximal tumor diameter but also the tumor volume.
Results: The median age of patients was 51.3 years and 145 patients (76%) were female. The median initial maximal tumor diameter and tumor volume were 5.5 mm and 48.8 mm3, respectively.
The tumor size increased in 27 patients (14%); Most patients, 23 in number, showed a tumor volume increase >50% without a maximal diameter increase of ≥3 mm. The other 4 patients had both an increasing tumor volume and increasing maximal tumor diameter ≥3 mm. One patient (0.5%) had newly appeared cervical lymph node (LN) metastasis at 3 years after the initial diagnosis.
There were no significant risk factors associated with increased tumor size, such as age, sex, or Hashimoto thyroiditis.
Twenty-four patients (13%) underwent delayed thyroid surgery at a median of 31.2 months and seven (29%) had cervical LN metastasis on pathologic examination.
Some PTMCs could grow significantly after a relatively short period of active surveillance. We also found that the change in tumor volume was more sensitive to detect tumor progression than the change in the maximal tumor diameter.