Isolated pulmonary metastasis occurring 10 years after total thyroidectomy and lymphadenectomy of a papillary thyroid carcinoma: a rare case report.

Background: Papillary thyroid carcinoma (PTC) is the most common types of thyroid cancer; and the 10-year survival rate vary from 85% to 100%. Although the prognosis of PTC is generally favorable, recurrence and metastasis occur in approximately 4.3% to 35% of cases. Lymph node metastasis is relatively prevalent, while distant metastasis is comparatively infrequent. Case Description: This case report details a 61-year-old female diagnosed with PTC. The patient's pathological stage was pT3aN1aM0, and according to the American Thyroid Association (ATA) risk classification, she was categorized as intermediate risk. The patient underwent total thyroidectomy and local lymph node dissection; however, radioactive iodine-131 treatment was not administered. Postoperatively, the patient regularly consumed levothyroxine sodium yet failed to have her thyroid hormone levels monitored. A decade following the surgical procedure, the patient presented with isolated lung metastasis. However, given the lengthy history of the patient's thyroid cancer, the clinical diagnosis initially entertained the possibility of a primary lung tumor. Subsequently, a wedge resection of the lung was performed on the patient, and the postoperative pathology confirmed metastasis of PTC. Conclusions: This rare case appears to indicate that patients with intermediate-risk PTC, as defined by the ATA, may benefit from postoperative radioactive iodine-131 treatment. Such treatment could potentially minimize the likelihood of tumor recurrence and metastasis to the greatest possible extent.