Papillary Thyroid Carcinoma: Four Cases Required Caution during Long-Term Follow-Up.

Due to the increased prevalence of papillary thyroid carcinoma (PTC), difficult cases and unexpected events have become more common during long-term follow-up. Herein we reported four cases that exhibited poor progress during long-term follow-up. All the cases were diagnosed with PTC and treated with total thyroidectomy before several years, and the patients had been newly diagnosed with recurrent and metastatic PTC. These four cases included recurred PTC with invasion of large blood vessels, a concomitant second malignancy, malignant transformation, and refractoriness to treatment. Physicians should closely monitor patients to promptly address unforeseen circumstances during PTC follow-up, including PTC recurrence and metastasis. Furthermore, we suggest that the development of a management protocol for refractory or terminal PTC is also warranted.