Case 2 is an 84-year-old man without remarkable medical history other than hyperlipidemia and prostatic hyperplasia. His chief complaint was cough, and an X-ray image showed an abnormal shadow on the upper mediastinum. A CT scan showed a 7.2 cm large mixed mass with a papillary solid component in the anterior mediastinum, and the trachea was compressed to the right and back. We could not confirm continuity with the thyroid; we found no lymph node metastases (Figure 3).
A PET-CT showed accumulation in the upper mediastinal tumor (SUVmax = 46.32) and pale nodules in the left lower lobe (SUVmax = 5.23; Figure 3). Neck ultrasonography revealed multiple nodules reminiscent of an adenomatous goiter in both lobes with no malignant appearance (the mediastinal tumors could not be visualized, and their continuity with the thyroid was unclear).
We performed endobronchial ultrasound-guided transbronchial needle aspiration (EBUS-TBNA) for diagnosis of the mediastinal tumor, but found no tumor cells, and the tumor's origin remained unknown.
In blood tests, the thyroid function was normal, but the thyroglobulin level rose to 2450 ng/mL. No other tumor markers were significant. We suspected that the mediastinal tumor originated from a thyroid cancer, and we decided to resect it.
The patient underwent total thyroidectomy, central neck dissection, and mediastinal tumor resection with sternal incision.
The mediastinal tumor adhered to the brachiocephalic artery and the right recurrent nerve on the right side, with the trachea and esophagus on the dorsal side and with the left recurrent laryngeal nerve on the left side. On the caudal side, a part of the thymus was resected together because the tumor also adhered to it.
Pathological findings included a fibrotic capsule and marked internal necrosis. The pathological report suggested a papillary carcinoma because of the preponderance of papillary growth and the presence of a papillary carcinoma nucleus (nuclear groove; Figure 4). We found no evidence of continuity between the mediastinal tumor and the thyroid. In addition, we noticed a 9 mm nodule in the isthmus of the thyroid and a nuclear finding of papillary carcinoma. We considered the nodule to represent a metastasis to the thyroid. We found no lymph node metastases. The thyroglobulin level decreased to 25.7 ng/mL after surgery. Administration of 131-iodine (100 mCi) resulted in strong accumulation in the thyroid bed and weak accumulation in lung metastasis. Therefore, we plan to follow-up the RAI therapy.