The patient, a 28-year-old man with a 3-month-old mass in the neck was referred to our department. The mass, located on the left thyroid lobe, was elastic, hard, showed limited mobility, and measured approximately 30 × 20 mm. There was no remarkable tenderness over the mass.\nBlood examination results were normal, including levels of thyroid-stimulating hormone, free thyroid hormone, and thyroglobulin (Table ). Ultrasonography revealed a hypoechoic solid mass in the lower pole of the left thyroid lobe with a poorly marginated heterogeneous pattern (Fig. ). Computed tomography revealed a heterogenic tumor in the left thyroid lobe (Fig. ). 18F-fluorodeoxyglucose (18F-FDG) accumulated in the thyroid tumor on positron-emission tomography. The standardized uptake value of 18F-FDG was 5.29 (Fig. ). Fine-needle aspiration cytology (FNAC) showed a number of lymphoid cells without atypia that were similar to those seen in malignant lymphoma of the thyroid (Fig. ).\nAs we diagnosed a highly malignant thyroid cancer (cT2N0M0), we performed a left hemithyroidectomy with central neck dissection (ND). Histopathological findings showed that the tumor was composed of irregular insular nests of neoplastic cells and had an expansive growth pattern in the thyroid (Fig. ). The carcinoma cells had round nuclei or polymorphonuclei with well-defined nucleoli and ill-defined cell borders (Fig. ). Immunohistochemical studies showed that the tumor was partially positive for CD5, positive for Ki-67 (approx. 30%), and negative for CD20, calcitonin, and thyroglobulin (Fig. ). Based on these histopathological findings, the tumor was finally diagnosed as CASTLE. There were no signs of recurrence without additional treatment after 10 years of follow-up.
Patient 3 was a 67-year-old female who presented with hoarseness and dysphagia for a few weeks. CT scans showed a 3.8 cm left thyroid tumor with superior mediastinal and tracheal involvements, i.e., stage pT4bN0M0. Complete resection of the tumor was successfully achieved by total thyroidectomy and central neck dissection. Postsurgical chemotherapy was applied (docetaxel 120 mg/m2 and cisplatin 30 mg/m2), followed by a course of intensity modulated radiotherapy (70 Gy at 2.5 Gy per fraction). She remains well 4 years after diagnosis.