Cystic metastases of papillary thyroid carcinoma mimicking a primary mediastinal cyst

Incidental Mediastinal Thyroid Cancer

Cystic mediastinal masses are most commonly benign congenital lesions. Rarely, a cystic mediastinal mass will prove to be malignant. The patient, a 50-year-old woman who initially presented with uveitis, was incidentally found to have a right paratracheal opacity on chest X-ray (CXR). Chest computed tomography (CT) demonstrated a 5cm right paratracheal hypodense cystic mass. The patient underwent a right robotic-assisted thoracoscopic resection of the mediastinal mass. Final pathology revealed a 4.5cm mass consistent with metastatic papillary thyroid carcinoma (similar histology in 2 excised lymph nodes). The patient subsequently had a total thyroidectomy with central and right neck dissections.

An unusual presentation of thyroid cancer

Well-differentiated thyroid cancers can present with nodal metastasis that have undergone cystic degeneration. Rarely, mediastinal nodes may undergo cystic changes and pose a diagnostic dilemma, especially if the primary lesion is occult. We describe the case of a patient who presented with a large mediastinal cystic lesion which turned out to be metastasis from thyroid cancer.