How reliable are tissue diagnosis of follicular thyroid carcinoma

In a study by Cipriani et al (1) in 2011 a pathology review of 66 follicular thyroid carcinoma (FTC) by three pathologists the diagnosis of 47 was changed (71 %).24 cases were reclassified to papillary carcinoma,18 to follicular adenoma, and five were reclassifed to poorly diffferentiated thyroid carcinoma ... A change from FTC to PTC (to follicular variant of papillary) is an order of magnitude less serious that changing the diagnosis from FTC to poorly differentiaed thyroid carcinoma.Further the change from Carcinoma diagnosis to thyroid follicular adenoma occured in 18 cases ,a change with obvious therapeutic implications.So in 23 cases (five plus eighteen ) the incorrect diagnoses have major and serious impact in almost half of the cases. FTC specific survival forthe reclassifed cases was 77% at ten years and 33.7 at 20 years. There are two major issues in which disagreement frequently occurs:1) whether or not there are areas of atypia as seen in papillary thyroid cancer and 2)whether or not there is invasion either of the capsule or angioinvasion. In some cases the reviewing pathologist believed that the invasion criteria used by some of the of pathologists were not sufficent and therfore the diagnosis was follicular adnoma. The cases were from well known and higly respected institutions ( MGH and University of Chicago) from 1965 to 2007 and all cases had undergone surgery and /or RAI treatment.The slides were reviewed by three pathologists from those institutions.You have to wonder what the error rate might be at the thousands of less pretigious institutions in the country and what the impact might be on patients whose diagnosis was wrong. .... If almost 3/4 of the diagnoses of FTC are on review found to be incorrect with with almost half being reclassified to papillary and around 10% being reclassifed to undifferentiated and about 30% not being carcinoma at all ( i.e. reclassified to adenoma) how accurate are the prognosis made on that basis and similarly how accurate are the data regarding effectivenss of various therapies. The recommendations of the American Thyroid Association as well as all other therapy recommending organizations begin with the implcit assumption that the diagnosis are correct, that is FTC is really that and not an adenoma with a excellent prognosis or a poorly differentiated carcinoma with a extremely bad prognosis regardless of therapy.You have to wonder how many patients with a benign adenoma underwent thyroidectomy and I 131 remnant ablation. If this study is representative of the general stratus of the pathological diagnosis of thyroid cancer how accurate could prognostic statements be ? 1 )Cipriani NA et al Follicular Thyroid carcinoma.How have histological diagnoses changed in the last half century and what are the prognostic implications? Thyroid, vol 25 number 11, nov 2015