Prevalence and Prognostic Significance of Poor Differentiation and Tall Cell Variant in Papillary Carcinoma in Japan

Excerpt

Our understanding of the outcomes and prognosis of papillary thyroid carcinoma continues to evolve. Certainly we have come a long way since the early 1970s when there was the simplistic view that all papillary thyroid cancer is either well differentiated, and hence almost all patients will have a very good prognosis, or has developed anaplastic change with an exceedingly poor prognosis. All pathologists now agree that there is a group of poorly differentiated thyroid cancers with a prognosis between well-differentiated (papillary or follicular) thyroid cancer and anaplastic cancer. However, the evolution of this concept has been a long and complicated process and marred by conflicting systems of grading. In 1983 Sakamoto et al. [1] first proposed pathologic criteria to define and distinguish poorly differentiated thyroid carcinoma. In 1984 Carcangiu et al. [2] also proposed criteria for poorly differentiated thyroid carcinoma, which they called “insular carcinoma.” Unfortunately, because the two groups were working independently, they used very different histopathologic criteria to define the entity. The result was almost 20 years of confusion during which there was a growing recognition of poorly differentiated thyroid carcinoma as an intermediate prognostic category but little uniformity in the pathologic criteria used for diagnosis. As a result there was conflicting data from different institutions on the incidence and significance of this diagnosis. …