Recurrent laryngeal nerve schwannoma adjacent to the thyroid: a case report

BACKGROUND: Schwannomas arising from the recurrent laryngeal nerve (RLN) are exceedingly rare tumors that can present diagnostic challenges when located adjacent to the thyroid gland. This case highlights the importance of considering neurogenic tumors in the differential diagnosis of paratracheal masses. CASE PRESENTATION: A 56-year-old Japanese woman was referred to our hospital after a routine chest radiograph revealed tracheal deviation. Computed tomography revealed a 4-cm mass along the left side of the trachea. Neck ultrasonography revealed a 37-mm lesion lateral to the inferior pole of the thyroid with cystic changes. Although a parathyroid tumor was considered, laboratory findings were not supportive, and fine-needle aspiration cytology was nondiagnostic. Surgical excision was performed for a definitive diagnosis and treatment. Intraoperatively, the tumor was extrathyroidal and contiguous with the RLN. The caudal end of the tumor extended close to the mediastinum, making dissection difficult. Therefore, the RLN was divided both cranially and caudally, and after tumor removal, the nerve stumps were reapproximated and sutured (neurorrhaphy). Histopathological examination confirmed the diagnosis of a schwannoma. The patient also had a history of cauda equina and posterior femoral cutaneous nerve tumors, suggestive of schwannomatosis (multiple schwannomas). At 24 months after surgery, no clinical or radiological evidence of recurrence was observed. CONCLUSIONS: RLN schwannomas are exceedingly rare; neurogenic tumors should be considered in paratrachyroid masses near the inferior pole, especially when imaging shows an extrathyroidal cystic lesion and cytology is nondiagnostic. Preoperative evaluation with ultrasonography and contrast-enhanced CT facilitates diagnosis, and surgical excision with nerve function preservation should be prioritized.