A Cervical Schwannoma Masquerading as a Thyroid Nodule

Abstract

Cervical schwannomas are common but rarely present as a thyroid nodule. We report here a lesion in a multinodular goiter yielding spindle cells on fine needle aspiration (FNA). A 60 year old woman with history of a goiter for 13 years noticed a significant increase in size of the goiter over a 3 years period and dysphagia for 1 year. She denied symptoms of hypo or hyperthyroidism. Thyroid was nodular and enlarged with retro-sternal extension. TSH = 0.31 IU/dl (n: 0.34-5.6 IU/dl), TT4 = 10.4 mcg/dl (n: 6.1-12.2 mcg/dl). Ultrasound guided FNA of a 4 cm hypoechoic left lobe nodule yielded cohesive spindle cells in a background of lymphocytes. On computed tomography, the thyroid was diffusely enlarged and heterogeneous. The left lobe extended to the retropharyngeal space and appeared to extend to the anterior mediastinum. The trachea was deviated to right side but remained patent. Differential diagnoses on FNA included schwannoma, melanoma, medullary (MTC) and anaplastic thyroid cancer. Immunohistochemistry was positive for S - 100 suggesting neural crest origin of the lesion. Negative staining for calcitonin, CEA, thyroglobulin, TTF1, melan A and HMB45 excluded melanoma, MTC and well differentiated thyroid cancer. Core biopsy of left lobe mass was consistent with a schwannoma. On MRI the left lobe mass was hyperintense on T2 weighted images and distinct from the thyroid. The mass extended from the skull base to the mediastinum. Intraoperatively the mass was found to be adherent to pharynx and esophagus but resectable. A subtotal thyroidectomy for multinodular goiter was performed. Resection of the intrathoracic component of the mass was deferred for future VATS. Based on operative findings, the most likely origin of the schwannoma was the pharyngeal nerve plexus. On histopathology, the schwannoma displayed spindle cells in whorls with Antoni A and B areas. The thyroid gland was diagnosed as a benign multinodular goiter. In the evaluation of a nodular goiter with an atypical presentation, pathology arising from other structures in neck, including nerve structures should be considered in the differential diagnosis. In addition to cytology and pathology, multimodal imaging may yield helpful clues.