Multimodal ultrasound imaging of primary thyroid schwannoma: A case report.

Rationale: Primary schwannoma of the thyroid gland is very rare, and its preoperative diagnosis is difficult.

Patient Concerns: We report the case of a thyroid nodule in an 18-year-old woman, who presented with a mass in her left neck with stiffness and normal thyroid function. However, the patient complained of numbness in her left upper extremity, and ultrasound (US) features were suspicious of malignancy.

Diagnoses: Multimodal US imaging was performed using B-mode, color doppler, ultrasonic elastography (UE), and contrast-enhanced ultrasound (CEUS). CEUS revealed heterogeneous enhancement and "target sign" within the tumor. The nodule was suspicious for malignancy and classified as TI-RADS 4b, while the elasticity values measured by UE indicated a benign lesion. Fine needle aspiration (FNA) was subsequently performed in the markedly contrast-enhanced area for biopsy. Cytological results revealed a benign schwannoma.

Intervention: The patient underwent left lobe resection. Postoperative pathology confirmed it to be a primary benign schwannoma of the thyroid.

Outcomes: After thyroidectomy, the patient was followed-up with US. At present, all laboratory tests and thyroid imaging are normal, and the numbness of the left upper limb has disappeared.

Lessons: The combination of different US modalities is useful for the diagnosis of thyroid lesions. FNA performed under CEUS guidance improves the accuracy of biopsy sampling.