Granular Cell Tumor of Thyroid Gland That Was Concomitant with Papillary Thyroid Carcinoma: A Case Report

Granular cell tumor (GCT) of the thyroid is rare and histogenesis of the carcinoma still remains poorly understood. Here in this study, we report a case of perithyroidal granular cell tumor in a 44-year-old woman, diagnosed as medullary carcinoma upon the interoperative frozen diagnosis. The tumor was comprised of white, solid mass with infiltrating margin in isthmus. Microscopically, the tumor revealed abundant eosinophilic cytoplasm, elongated nucleus and eosinophilic amyloid-like materials. It was composed of diffuse sheets of polygonal cells with abundant eosinophilic cytoplasm and cytologically bland nucleus on permanent section. On immunohistochemical staining, S-100 and CD68 are diffusely positive. Determining the progression and the behavior of the tumor is critical for providing long-term management and preventing aggressive treatment.