P-85 Inflammatory myofibroblastic tumor: An extremely rare tumor of the thyroid gland poses challenges in diagnosis and management

Abstract

Abstract Introduction Inflammatory myofibroblastic tumor (IMT) is an exceedingly rare mesenchymal tumor characterized by myofibroblastic spindle cells and an inflammatory cell infiltrate. The clinical presentation of IMT in the thyroid gland varies widely, ranging from an asymptomatic thyroid nodule to a diffuse, rigid, fixed, and painful mass. While IMT of the thyroid gland is generally considered a benign borderline tumor with very low metastatic potential, its diagnosis and management can be intricate. Surgery remains the preferred treatment, with recurrence being rare following successful removal. Nonetheless, the optimal management of residual tumors is contentious and may involve a second surgery or the use of immunosuppressants and chemotherapeutic agents. Clinical Case A 47-year-old female patient presented with painless discomfort and stiffness around the thyroid gland. A neck ultrasound revealed a hypoechoic nodule measuring 21×12 mm on the left lobe and a hypoisoechoic heterogeneous nodule 35×28 mm in size on the right lobe of the thyroid gland. These nodules displayed low vascularity, and no pathologic lymph nodes were detected. Fine needle aspiration biopsies (FNABs) were performed on the nodules in both lobes at different times, indicating thyroiditis in the right lobe and spindle-shaped cells with atypia of uncertain significance in the left lobe. Subsequent evaluation of FNAB materials at a referral center suggested a high suspicion of lymphoid malignancy. The patient underwent thyroidectomy; however, the surgeon chose to preserve the left thyroid lobe due to its extreme fibrotic and stone-like consistency, thereby preserving recurrent laryngeal nerve function. Histological analysis confirmed the presence of an inflammatory myofibroblastic tumor characterized by spindle cells accompanied by abundant histocytes, plasma cells, and lymphocytes. The tumor cells exhibited positivity for SMA. Postoperative ultrasound revealed a residual tumor approximately 2 cm in size located in the left isthmus and adjacent left lobe, which remained stable over a 6-month follow-up period. Conclusion Our case highlights the potential for misdiagnosing IMT of the thyroid gland as malignant thyroid tumors. Furthermore, the management of a residual tumor presents a complex clinical challenge. The surgical team is reluctant to pursue a second surgery due to potential risks to recurrent laryngeal nerve function. In this session, we aim to solicit expert opinions and engage in interactive discussions regarding the management of the residual tumor in this specific case.