Anterior Neck Swelling in a 3-Year-Old Female

Case Presentation:
A 3-year-old female presented with an anterior neck swelling of unspecified duration. She had no associated symptoms, and her thyroid function tests were within normal limits, with a thyroid-stimulating hormone (TSH) level of 0.98 and free thyroxine (FT4) of 18.

Imaging Findings:
A neck ultrasound revealed a single, well-defined, solid isoechoic nodule measuring 16x6x5 mm located in the mid to lower third of the left thyroid lobe. The nodule was classified as a TI-RADS 3 lesion, suggesting a low risk of malignancy.

Multidisciplinary Team Decision and Surgical Management:
Given the characteristics of the nodule and the patient’s young age, the case was discussed in a Multi-Disciplinary Team (MDT) meeting. A decision was made to proceed with a left thyroid lobectomy to obtain a definitive diagnosis and rule out malignancy. The surgery was performed without complications.

Histopathological Examination:
The histopathology report confirmed the presence of benign active intrathyroidal thymic tissue with no evidence of malignancy.

Conclusion:
This case highlights a rare but benign condition, where intrathyroidal thymic tissue mimics a thyroid nodule in a pediatric patient. The diagnosis was confirmed postoperatively, and no further intervention was required.

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