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3128247 
Journal Article 
Changes in classification of follicular thyroid cancers 
Hakala, TT; Kholová, I 
2016 
1 
Thyroid
ISSN: 1050-7256
EISSN: 1557-9077 
English 
27043936 
During the last decades the histopathological classification of thyroid gland tumors has changed with stricter criteria for follicular thyroid carcinoma (FTC), an establishment of poorly differentiated carcinoma and superposition of nuclear atypia of papillary thyroid carcinoma (PTC) above architecture. Furthermore, an increase in imaging of neck area revealed the frequency of thyroid nodules, which nevertheless harbor cancer only in 5% of the cases. In recent issues of Thyroid, both thyroid cancer epidemiology and FTC reclassification were interestingly covered (1,2). Vaccarella et al. estimated that diagnostic changes may account for ≥60% of thyroid cancer cases diagnosed during recent years in certain developed countries. In a study by Cipriani et al., FTC cases diagnosed during 1965-2007 were re-evaluated by three pathologists. A remarkable 71% of FTC cases were re-classified as follicular adenomas or PTCs. Elimination of follicular adenomas and PTCs led to decreased survival of re-classified FTC patients. Inter- and intraobserver variability in histologic interpretation leads to diagnostic challenges in follicular lesions. We analyzed thyroid cancer in Pirkanmaa region of Finland. During 1981-2002, a total of 495 patients with differentiated thyroid cancer were treated in Tampere University Hospital, Finland (3). We performed registry-based follow-up until December 2011. In our material, 71 (13%) tumors were initially classified as FTCs. In the patient with FTC, disease-specific mortality was 19 (27%) and overall mortality 38 (54%) cases. We performed re-classification of FTCs according to latest WHO guidelines with following results: five (7%) of 71 tumors were re-classified to follicular adenomas and 3 (4%) tumors were reclassified as PTCs. None of the re-classified cases with follicular adenoma or PTC died of thyroid malignancy. In re-classified FTC patients, 19 (30%) patients had FTC-related death, and overall mortality was 36 (57%) cases during the observation period. Our results corroborate that the diagnosis of FTC in may be inaccurate in previous pathology reports. However, in our series, the number of re-classified cases was only 8 out of 71 (11%). These figures are much lower than in the study of Cipriani et al., in which considerable 71% of FTC cases were re-classified to follicular adenomas or PTCs.