Thyroid-bed schwannoma mimicking a thyroid neoplasm: a case report

Intrathyroidal schwannomas are rare, and thyroid-bed schwannomas are scarcer, with merely a few case reports and tough preoperative differentiation. We report a 33-year-old female with a swallowing-movable left neck mass and normal thyroid function. Gray-scale B-mode ultrasound, color Doppler flow imaging and contrast-enhanced ultrasound showed showed a heterogeneously enhanced TI-RADS 3 lesion preoperatively suspected as a follicular neoplasm. Fine-needle aspiration (FNA) biopsy was performed, which failed to yield a definitive pathological diagnosis and yielded Bethesda category I. She received left lobectomy plus isthmectomy, and pathology confirmed thyroid-bed schwannoma sparing thyroid parenchyma; she recovered well with normal thyroid function postoperatively. Due to its low incidence, this tumor is often mistaken for an intrathyroidal nodule on ultrasound. Total surgical excision is the first-line therapy with good overall prognosis. Unlike intrathyroidal schwannomas, most thyroid-bed lesions can be enucleated alone without routine thyroidectomy; hemithyroidectomy is needed for dense adhesion, and total thyroidectomy is rarely required. Considering the low diagnostic value of FNA, multidisciplinary consultation of pathology, radiology and surgery is advised for lesions with atypical imaging, inconclusive FNA or ill-defined thyroid margins. Ultrasound-guided core needle biopsy (CNB) should be performed if needed to tailor proper treatment.