Morphological and immunohistochemical analysis in encapsulated follicular variant papillary thyroid carcinoma, invasive follicular variant papillary thyroid carcinoma and a new entity: non-invasive follicular thyroid neoplasm with papillary nuclear feature.

Thyroid cancers are the most common endocrine organ cancers. Encapsulated follicular variant papillary thyroid carcinomas (EFVPTC) are quite slow (indolent). Non-invasive follicular thyroid neoplasm with papillary nuclear feature (NIFTP) is a new entity identified as a result of studies in recent years. If the patient instead of EFVPTC develops NIFTP, cancer will not be recognized and the treatment will change. Three groups, in which CD44, p53, Ki-67, p27, HBME-1, galectin-3, cytokeratin-19, CD56 were used as markers, were evaluated. Nuclear score assessment was also conducted in the NIFTP group. The results were compared with each other. Significant differences were detected in the intensities and percentages of CK19, HBME-1, CD56, CD44 staining and galectin-3 staining intensity. In group 1, cytokeratin-19, galectin-3, HBME-1 and CD44 expression were not as low as in the other groups, while CD56 staining was detected more frequently. p53, p27 and Ki-67 staining showed no obvious expression differences between the groups. The NIFTP group showed different IHC results compared to encapsulated invasive FVPTC and common invasive FVPTC. When evaluating whether the IHC expression patterns used in PTCs differ in NIFTP cases, it was found that CD44 could serve as an additional IHC stain that may guide pathologists during the diagnosis.