Aspiration cytopathology of metastatic mucinous papillary thyroid carcinoma

The light microscopic histopathology and cytopathology of papillary thyroid carcinoma (PTC) and its variants is amply depicted in reviews, basks, and hook chapters, One of the changes in PTC, however, that is infrequently dis cussed or illustrated in the literature is that of mucinous metaplasia. In the aspiration cytopathology literature, we are aware of only a rare report of PTC exhibiting extensive mucinous metaplasia. We present an example cor relating the histopathology and fine needle aspiration cytopathology of a P TC that had metastasized on several separate occasions to cervical lymph no des, and in the process demonstrated mucinous transformation. Without a pri or history of PTC, the aspirate smears and tissue sections could have been mistaken easily for metastatic clear cell carcinoma of non-thyroidal origin . Mucinous metaplasia represents an extremely uncommon, but nonetheless pot ential, pitfall in the aspiration cytopathology and histopathology of metas tatic PTC.