[Intra-thyroid metastasis and the pathologist]

Intra-thyroid metastases (ITM) are rarely observed clinically. The high blood flow of the thyroid and its high content of iodine explain this rarity. The clinical and radiological criteria of ITM are not very specific. The pathologist is the principal actor of ITM diagnosis. Cytology, intraoperative examination and histological techniques are the means available. The microscopic aspects of ITM are varied. Art is to differentiate ITM to undifferentiated primary tumor. We report two cases of ITM in patients aged 49 and 52 years, respectively. We discuss diagnostic methods and challenges for pathologists in identifying such lesions.