Endocrine Abstracts

Background: Distant metastasis, as the initial manifestation of papillary thyroid cancer (PTC), is uncommon. Here, we present two unusual cases of large cystic mediastinal lesions, with histology indicative of metastasis from PTC as first diagnosis.

Case presentation: We present two male patients, aged 46 and 50 years old, who were referred to our department. The first patient, complained of persistent cough and underwent a thorax CT which revealed a large 10 cm cystic mass. Due to compressive symptoms, he underwent surgical excision of the cystic mass. The histopathology revealed neoplastic cells in the lining of the cyst, with positive immunohistochemistry for TTF-1 and PAX-8. Additionally, two lymph nodes were found in the surrounding fat tissue, constituted of cells of epithelial origin, positive in thyroglobulin (Tg), TTF-1 and PAX-8. The second patient presented with similar symptoms (persistent cough, shortness of breath in minimal exercise) and underwent a thorax CT. A large cystic mass of 8.2 cm was revealed in the mediastinum, which was surgically removed. The histopathology identified a cyst with peripheral lymphocytes and the presence of two neoplastic lesions in the surrounding fat tissue, consisting of epithelial cells with papillary architecture and positive immunochemistry in Tg and TTF-1. The work-up that followed included imaging of the thyroid by ultrasound, identification of suspicious lesions and total thyroidectomy. In the first case, a 6.7 cm PTC of tall cell variant was revealed. In the second case, the histopathology indicated a multifocal PTC metastatic to cervical lymph nodes. They both received a therapeutic dose of radioidine ablation (100 mCi). Imaging, six months after the diagnosis, did not reveal any further metastases. At present, nearly a year after operation, both patients receive thyroxine suppression therapy and are on close monitoring including measurement of thyroglobulin levels, thyroid ultrasound and thorax CT imaging.

Conclusions: In the literature, mediastinal lesions related to thyroid cancer are uncommon. However, thyroid cancer may present with extracervical manifestations such as mediastinal lesions, which probably represent the cystic degeneration of mediastinal lymph nodes. Therefore, thyroid cancer may be a part of the differential diagnosis of cystic mediastinal lesions.