Ought to the changes within the immunophenotype of solid cell nests (SCNs) and follicular cells in hashimoto's thyroiditis be considered as premalignant lesions?

Background: Papillary thyroid carcinoma (PTC) is more frequently reported in patients with Hashimoto's thyroiditis (HT), which may be associated with the presence of solid cell nests (SCNs) and focal PTC-like nuclear alterations in the thyroid gland. The point of this consideration was to assess the morphological and immunohistochemical features of SCNs and follicular epithelial changes in Vietnamese patients with HT. Materials and Methods: Hematoxylin–eosin and immunohistochemistry were performed on 20 samples of HT patients who underwent thyroidectomy and were diagnosed with Hashimoto's thyroiditis at Military Medical Hospital 103 from 6/2018 to 6/2019. The expression of five markers (P63, Calcitonin, TTF1, CK19 and HBME-1) in SCNs and follicular epithelial changes were evaluated. Results: Ninety per cent of samples had SCNs with an average of 10 SCNs per section. Only type 1 and type 4 SCNs were presented (85% and 55%, respectively) and all SCNs were composed of main cells (p63-positive). Fifteen of the 18 cases having SCNs possessed nuclear features of PTC. C-cell hyperplasia was found in one case with 20 clusters. All SCNs showed strong staining with CK19 and weak staining with HBME-1. Follicular epithelial changes were Hürthle cell metaplasia, PTC-like nuclear alterations, atypical solid nodules, papillary and glomerular-like forms (40%, 100%, 25% and 50%, respectively). Follicular cells of glomerular-like forms (new alteration) especially were positive with CK19 (2+ ~ 3+), HBME-1 (1+) and TTF1, while the components in these follicles were negative with CK19, HBME-1 and TTF1. Among PTC-like nuclear alterations, all the atypical solid nodules related to HT showed markers related to PTC and without SCNs. Conclusions: Increasing the number of SCNs, as well as PTC-like nuclear alterations of main cells in SCNs and follicular epithelial changes were co-expressed CK19 and HBME-1. Therefore, the need for HT management should be considered. [ABSTRACT FROM AUTHOR]