Endocrine Abstracts

Background

The latest WHO classification of tumours of endocrine organs defines new units of borderline thyroid tumours (BTT) of uncertain biological behaviour. The aim of our study was to evaluate ultrasonographic, cytological features, mutation profile and surgery treatment in patients with these rare tumours.

Methods

The analysis of 8 out of 487 operated patients, who underwent thyroid surgery between June 2016 and June 2020. The definitive diagnosis was made postoperatively by extensive histopathological examination. Molecular genetic analysis of genes associated with thyroid oncology (BRAF, HRAS, KRAS, NRAS, TERT, TP53, fused genes) was performed from one FNAB and 7 formalin-fixed paraffin-embedded (FFPE) samples.

Results

BTT were found in a total of 8 patients (1, 6%), with a predominance of men (6 men/2 women) in contrary to other operated patients. Preoperative cytological samples were classified in the Bethesda system as non-diagnostic (Bethesda I), benign (Bethesda II) and atypia/follicular lesions of undetermined significance (Bethesda III) in one, four and three cases, respectively. Hemithyroidectomy was performed in four cases and total thyroidectomy in four patients. The definitive histological diagnosis revealed non-invasive encapsulated follicular neoplasm with papillary-like nuclear features (NIFTP) in three patients, follicular tumour of uncertain malignant potential (FT-UMP) in three patients, well differentiated tumour of uncertain malignant potential (WDT-UMP) in one patient and hyalinizing trabecular tumour (HTT) in one case. The patients with NIFTP had mutations in HRAS - in one patient also in combination with pathogenic variant in TP53 gene and mutation in NRAS gene in two patient was detected and in HTT patient PAX8/GLIS3 fusion gene was detected from the surgically removed tissue. In remaining four cases, no somatic pathogenic mutations or fusion genes were found.

Conclusion

The surgical treatment of borderline thyroid tumours (BTT) is necessarily individual. It is influenced by preoperative clinical, ultrasonographic, cytological and molecular genetic findings, as well as the presence of other comorbidities.

Key words

borderline thyroid tumour, thyroid FNAB, molecular testing of thyroid tumours, thyroid surgery.