Granular Cell Tumor of Thyroid: Challenging Pitfalls and Mimickers in Diagnosis.

Mesenchymal tumors of the thyroid are extremely rare. Only few isolated cases of primary thyroid granular cell tumor (GrCT) have been reported. The anatomic location of this lesion plays an important role in the differential diagnosis. It is well-known that GrCT commonly involves the head-and-neck region, lower extremity, nuchal region, chest wall, and internal viscera such as the gastrointestinal tract. However, primary GrCT of the thyroid are unexpected and might lead to misdiagnosis, especially with pathological diagnosis limitations such as frozen section and fine-needle aspiration. We believe that it is important to establish a good differential diagnosis because of its ability to simulate the appearance of invasive carcinoma, especially in cases lacking tissue block examination. In this paper, we try to focus on clinical, radiological potential characteristics, and the differential diagnosis of the tumor.