Ectopic Thyroid Tissue Presenting as Thoracic Extradural Cystic Lesion in a Child: A Rare Case Report

Ectopic thyroid tissue is a rare developmental anomaly resulting from aberrant migration of the thyroid gland during embryogenesis. Although ectopic thyroid tissue is most commonly identified in the lingual region, it may rarely occur at distant anatomical sites. We report a rare case of ectopic thyroid tissue presenting as a thoracic extradural cystic lesion in a 12-year-old girl.
The patient presented with progressive difficulty in walking, bilateral lower limb weakness, and stool incontinence of one month's duration. Magnetic resonance imaging revealed a loculated extradural cystic lesion extending from D2 to D8 vertebral levels, causing significant spinal cord compression and radiologically suggestive of an arachnoid cyst. The patient underwent D3–D7 laminectomy and excision of the lesion. Histopathological examination demonstrated thyroid tissue composed of colloid-filled follicles. Immunohistochemistry showed strong positivity for thyroid transcription factor-1 (TTF-1) and thyroglobulin, with focal cytoplasmic and membranous positivity for CK19, diffuse membranous positivity for CD56, and reduced galectin-3 expression, supporting the diagnosis of ectopic thyroid tissue.
Extensive evaluation to exclude a primary thyroid malignancy, including thyroid function tests, ultrasonography, contrast-enhanced computed tomography of the neck, positron emission tomography-computed tomography, and subsequent thyroidectomy, revealed no evidence of malignancy within the orthotopic thyroid gland. The patient showed neurological improvement following surgical decompression.
This case highlights an exceptionally rare presentation of ectopic thyroid tissue in a pediatric patient and underscores the importance of histopathological examination and immunohistochemistry in establishing the diagnosis of unusual spinal lesions

Ectopic thyroid tissue; Thoracic extradural lesion; Spinal cord compression; Immunohistochemistry

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