Endocrine Abstracts

Background: Nonivasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) and hyalinizing trabecular tumor (HTT) are a rare follicular- derived thyroid neoplasmas with indolent clinical behavior. These tumors are encapsulated or clearly delimited and distinguished by detail using histopathological criteria.

Method: Description of two cases of these rarer tumors, classified on FNAB Bethesda III AUS/FLUS in the BSRTC 2017 and diagnosed after total thyroidectomy.

Results: Two cases of classified Bethesda III with ultrasonography guided FNAB were investigated using molecular genetic methods and histopathology verification: In a 61-year-old man following the category Bethesda III system histopathology investigation detected nonivasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTPs) in the terrain of polynodous nodular goitre. There was only minimum of colloid in the microfolliculles but nuclei were slightly enlarged, non-round and ovrlapping. Molecular genetic investigation found c.182A>G p.(Gln61Arg) in the exon 3. somatic mutation of the gene NRAS. In a second patient, a 48-year-old man solitary isthmic nodule classified Bethesda III. The postoperative histological finding expressed suspicion of medullary carcinoma. But angioinvasion was not shown and amyloid staining was negative. Supervision by an experienced thyroid pathologist was required. Immunohistochemistry: calcitonin, CEA- negative; thyroglobulin TTF1-positive, NES dispersive positive. Ki-67 unique pattern of membranous positivity characterizing hyalinizing trabecular tumour. (HTT). Molecular genetic analysis c.394G > Ap.(Glu132Lys) in the exon 4. somatic mutation of the gene NRAS. Conclusions. In these two rarer tumours with Bethesda III diagnosis total thyroidectomy was chosen as the best option due to risk of possible multifocal involvement in the terrain of nodular goitre, age and male sex with a longer duration and size progression of the nodules. In case of postoperative histological finding of thyroid malignancy, completion thyroidectomy bears higher risk of postoperative complications and the patient is exposed to greater psychological stress.