title: Poorly differentiated thyroid carcinomas: how much poorly differentiated is needed?
abstract: BACKGROUND
  Poorly differentiated (PD) carcinomas of the thyroid are conceptually situated between well-differentiated (papillary or follicular) carcinomas and anaplastic thyroid carcinomas. Although the morphologic criteria for PD tumors are well defined, it is not clear how much of a PD area besides a well-differentiated component in a given tumor is required to allow such a diagnosis.
  
  
  METHODS
  We identified 42 patients suffering from thyroid carcinoma with an adverse clinical outcome. Fifty patients with follicular carcinoma were added as controls. We analyzed poorly differentiated areas by applying the Turin criteria of PD carcinomas. These criteria consisted of the presence of a solid/trabecular/insular growth pattern, lack of nuclear features of papillary carcinoma, and presence of 1 of the following features: (1) convoluted nuclei, (2) tumor necrosis, (3) 3 or more mitoses per 10 high-power fields.
  
  
  RESULTS
  Using a cutoff value of 10% of PD areas per examined tumor surface, we identified a total of 35 PD carcinomas. Despite using a threshold of 10% of the tumor area as poorly differentiated, the survival data in a Kaplan-Meier analysis were significantly worse than those in the control group (P<0.001) and did not differ from tumors with a PD area >50%. In a multivariate analysis that included age, sex, tumor stage, and PD area >10% against survival data, the only consistent significant factor was PD differentiation (P<0.001).
  
  
  CONCLUSIONS
  As even slight amounts of PD areas (≥ 10%) in a thyroid carcinoma affect the prognosis significantly, the presence of such areas may be worth reporting in thyroid carcinomas.
authors: Institute of Pathology, University of Bern, Triemlispital, Zürich. dettmerms@upmc.edu
authors: Matthias
authors: M
authors: Dettmer
authors: Anja
authors: A
authors: Schmitt
authors: Hans
authors: H
authors: Steinert
authors: Andreas
authors: A
authors: Haldemann
authors: Andreas
authors: A
authors: Meili
authors: Holger
authors: H
authors: Moch
authors: Paul
authors: P
authors: Komminoth
authors: Aurel
authors: A
authors: Perren
mesh_terms: D018263:Adenocarcinoma, Follicular / Q000473:pathology; D002291:Carcinoma, Papillary / Q000473:pathology; D002454:Cell Differentiation; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D008875:Middle Aged; D009367:Neoplasm Staging; D011379:Prognosis; D016016:Proportional Hazards Models; D013964:Thyroid Neoplasms / Q000401:mortality / Q000473:pathology*