Poorly Differentiated Thyroid Carcinoma: An Incubating Entity

as the fifth most expected malignancy in American women. Although thyroid cancer is not infrequently diagnosed, it rarely bests its host. We understand a great deal about well-differentiated thyroid cancers, including carcinomas of the thyrocyte and parafollicular c-cells. We have identified a number of mutations and gene rearrangements responsible for familial and sporadic tumors. We have postulated about mechanisms of spread and are able to predict biological behaviors of particular cancer types. However, gray zones remain, and as physicians and scientists, we are never comfortable with these gray zones, as they potentially contain magical epitopes for disease eradication and serve as pesky reminders that medicine is not an exact science. In thyroid cancer, poorly differentiated thyroid carcinomas (PDTC) represent the bridge between more well differentiated malignancies of thyrocytes and the undifferentiated (anaplastic) thyroid carcinomas. Six years ago in Turin, a group of expert surgical pathologists set the stage for refining the diagnosis of PDTC, as introduced by the WHO in 2004, rather than it serving as a diagnosis for those entities which had “high grade features” but did not fit neatly into one of the other defined categories. The conundrum that now exists is the incubation period between the birth of this now well-defined category of thyroid malignancy and the application of the diagnostic criteria, outcomes going forward, and how this diagnosis becomes translated into action by clinicians treating the entity.