Inflammatory Myofibroblastic Tumor of the Thyroid Gland: A Brief Case Report

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/ by-nc/3.0) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited. Inflammatory myofibroblastic tumor (IMT), also known as inflammatory pseudotumor (IPT) or plasma cell granuloma (PCG), is a histologically distinctive lesion that occurs primarily in the viscera and soft tissue, but has been reported in nearly every site in the body. 1 Until now, only 19 cases of IMT that have involved the thyroid have been reported in the English literature. 2 Moreover, most cases in the thyroid have been described as cases of PCG, 2 and the myofibroblastic component in the thyroid cases is usually not prominent. Only one case has reported IMT of the thyroid gland. 3 This study reports and discusses the differential diagnosis of an IMT of the thyroid gland that occurred in a 50-year-old Korean woman and which showed a predominantly myofibroblastic proliferation. A-50-year-old female presented with a right thyroid mass and did not have a history of Hashimoto's thyroiditis. All routine laboratory findings and thyroid function tests were normal. Ultrasonography revealed a 0.6×0.6-cm lobulated hypoechoic mass in the right lobe and a 0.6×0.5-cm oval hypoechoic mass in the left lobe (Fig. 1). Fine-needle aspiration cytology of the right thyroid mass showed as a Hurthle cell type follicular neo-plasm. Fine-needle aspiration or biopsy was not performed in the left thyroid. The patient underwent total thyroidectomy under general anesthesia. The total thyroidectomy revealed two nodules in both lobes. A well-defined, solid, tan-colored encapsulated lesion that measured 0.6 cm at its greatest diameter was observed grossly in the right lobe. Histopathology revealed follicular adenoma. In the left lobe, a well delineated, but unencapsulated lesion that measured 0.6 cm at its greatest diameter was present (Fig. 2A). The lesion was characterized by poorly defined spindle cells with slightly pleomorphic nuclei (Fig. 2B). Histiocytes were frequent and often contained fine hemosiderin granules (Fig. 2C). There were a few lymphocytes or plasma cells and the le-sion did not have any mitotic figures or lymphovascular invasion. The trapped residual thyroid follicular cells had no characteristic cytological findings of papillary carcinoma (Fig. 2D). The remaining thyroid tissue showed no pathological findings. Immunohistochemical analysis indicated that the spindle cells were positive for α-smooth muscle actin, but negative for cytokeratin (CK), CK19, epithelial membrane antigen, thyroid transcription factor-1, …