Poorly Differentiated Thyroid Carcinoma

Abstract

Poorly differentiated thyroid carcinomas are diagnostically controversial, as there is a lack of consensus regarding diagnostic criteria. Poorly differentiated thyroid carcinomas usually occur in older patients (>50 years) and are more common in Italy and Latin America (4–7 % of thyroid carcinomas) and less common in the United States. These tumors are morphologically and prognostically intermediate between well-differentiated and anaplastic thyroid carcinoma. An operational pathologic definition offered in 2007 included insular and trabecular variants, but not solid lesions or more differentiated tumors that may have a poor prognosis, such as tall cell, columnar, diffuse sclerosing, and oncocytic lesions. At a consensus conference in Turin in 2006, 12 thyroid pathologists evaluated 83 tumors without knowledge of clinical parameters and devised a diagnostic algorithm for the diagnosis of poorly differentiated thyroid carcinoma to include “(1) presence of a solid/trabecular/insular pattern of growth, (2) absence of the conventional nuclear features of papillary carcinoma, and (3) presence of at least one of the following features: convoluted nuclei; mitotic activity ≥3×10 HPF [high-power fields]; and tumor necrosis.”