Poorly Differentiated Thyroid Carcinoma. Are We There Yet?

The article reviews the controversial area of poorly differentiated thyroid carcinoma. Consensus criteria that define poorly differentiated thyroid carcinoma have been published in 2007. According to these, poorly differentiated thyroid carcinoma is a distinct histotype and the term poorly differentiated should not be used as a synonym for high-grade thyroid cancer. Data in the literature show that tumor necrosis and high mitotic activity, but not growth pattern or histologic subtype, are prognostic markers for thyroid tumors. This underscores the importance of grading to identify thyroid carcinomas that behave aggressively. The issue of grading versus typing thyroid tumors is discussed.