Background: Primary schwannomas of the thyroid gland are extremely rare. These tumors most often present as asymptomatic solitary neck masses, slow growing and rarely malignant. Only 15 cases of intrathyroidal schwannoma have been reported in the literature, and few have been reported with fine needle aspiration (FNA) cytology.
Case: A 14-year-old male patient presented with an asymptomatic left intrathyroidal mass. Radiologic studies revealed a circumscribed, marked hypoechoic mass with cystic portions in the left lobe of the thyroid gland on ultrasonography, pushing the trachea toward the right, visible side on computed tomography. FNA cytology of the mass exhibited a paucicellular smear composed of predominantly round to oval-shaped cells and occasional ovoid to spindle-shaped cells in loosely cohesive aggregates. On pathologic examination, the mass measured 60 x 45 x 30 mm and consisted of spindle-shaped cells arranged in fascicles in a whorling pattern in association with alternating hypercellular and hypocellular areas.
Conclusion: Awareness of and understanding of the cytopathologic and radiologic characteristics of this entity are helpful in preoperative evaluation and correct treatment of intrathyroidal schwannoma.