Case report: different metastatic components from anaplastic thyroid carcinoma in mediastinal and neck lymph nodes simultaneously diagnosed by FNA.

Anaplastic thyroid carcinoma (ATC) is a rare but aggressive form of undifferentiated thyroid carcinoma which arises from previously well-differentiated thyroid carcinomas, such as papillary carcinoma or follicular carcinoma. We report on an interesting case of ATC found in an enlarging neck mass with metastatic papillary carcinoma found in mediastinal lymph nodes sampled by endoscopic bronchial-ultrasound guided- fine-needle aspiration, due to the incidental finding of a lung mass by CT scan. Divergent morphologies on cytology preparations were resolved by immunohistochemistry, which aided in the identification of both sites of malignancy and the common thread between them. The eventual palliative resection demonstrated the various components including undifferentiated thyroid carcinoma, papillary carcinoma, and background lymphocytic thyroiditis.