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Long-Term Follow-Up Ultrasonographic Findings of Intrathyroidal Thymus in Children
Yun Woo Chang1, Hee Min Kang2, Eun Ji Lee2
1Department of Radiology, Soonchunhyang University Hospital Seoul, Seoul, Korea. ywchang@schmc.ac.kr.
Insights
Intrathyroidal thymus in children may shrink and develop indistinct margins over time. Increased age at follow-up is linked to changes in echogenicity of these thyroid lesions.
Area of Science:
- Pediatric Radiology
- Endocrinology
- Thyroid Imaging
Background:
- Intrathyroidal thymus is a rare finding in children, often incidentally detected during thyroid ultrasonography.
- Understanding its long-term sonographic evolution is crucial for accurate diagnosis and management.
Purpose of the Study:
- To analyze the long-term sonographic findings and evolution of intrathyroidal thymus in children.
- To identify associations between sonographic changes and patient age.
Main Methods:
- Retrospective analysis of thyroid ultrasonography (US) in 41 children diagnosed with intrathyroidal thymus.
- Long-term follow-up US data from 26 patients (aged 1-14 years) were compared with initial scans.
- Statistical analysis included chi-squared tests and logistic regression to assess changes in size, shape, margin, and echogenicity in relation to age.
Main Results:
- Over time, 42.3% of intrathyroidal thymus lesions decreased in size, with one disappearing.
- Margins became indistinct in 38.5% of cases, and 23.1% showed a change to hyperechogenicity.
- Decreases in size were significantly associated with indistinct margins (p=0.004), and increased age at follow-up correlated with hyperechogenicity (OR=2.141, p=0.017).
Conclusions:
- Intrathyroidal thymus in children can exhibit dynamic sonographic changes, including size reduction and margin blurring.
- Echogenicity changes towards hyperechogenicity are associated with increasing patient age.
- These findings aid in differentiating intrathyroidal thymus from other thyroid pathologies on long-term follow-up.
Objective:
To analyze long-term follow-up sonographic findings of intrathyroidal thymus in children.
Materials And Methods:
Among 1259 patients with congenital hypothyroidism under 15 years of age who underwent thyroid ultrasonography (US), 41 patients were diagnosed with an intrathyroidal thymus based on US criteria, i.e., hypoechoic solid lesion with punctate and linear echogenicity. In 26 patients aged one to 14 years old, the last follow-up US was performed after 6 to 132 months and compared with the initial US. The lesion was considered to decrease in size if there was a change of more than 2 mm in any dimension. The margin change was divided into well-defined and indistinct, blurred. When the echogenicity changed to a hyperechoic from a characteristic thymic echogenicity pattern, the pattern was considered a hyperechogenic. The changes in size were compared with the changes in shape, margin, and echogenicity pattern. The changes in size, shape, margin, and echogenicity were analyzed the association with the age of last follow-up. Statistical analysis was conducted using the chi-squared test and logistic regression.
Results:
Fifteen (57.7%) cases were stable in size, and 11 (42.3%) decreased in size, including one that disappeared. Ten (38.5%) cases changed to indistinct margins from initially well-defined margins including one case of initially indistinct margin. Six (23.1%) changed to hyperechogenic, from initially characteristic thymic echogenicity patterns. When follow-up change was compared, decreases in size were significantly associated with lesion changes to indistinct margins (p = 0.004). The age at last follow-up was significantly associated with change to hyperechogenicity (odd ratio, 2.141; 95% confidence interval, 1.144-4.010, p = 0.017).
Conclusion:
On follow-up US, an intrathyroidal thymus may be decreased in size, with indistinct margins, or show changes to a hyperechoic mass. Decreases in size may be associated with changing to indistinct margins, and changes to hyperechogenicity may be associated with increasing age.
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