Endocrine Abstracts

Background: Noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) is a newly described indolent thyroid tumor with well-defined histopathological diagnostic criteria. Even though the histopathologic features and diagnostic criteria for NIFTP are well-established, preoperative diagnosis using sonographic or fine needle aspiration findings has yet to be confirmed. The aim of this study is to compare the clinical, sonographic, and cytological characteristics of NIFTP with minimally invasive encapsulated follicular variant of papillary thyroid carcinoma (EFVPTC).

Methods: We examined the records of 73 patients who underwent thyroid surgery at Hacettepe University Hospital between 2016 and 2022 with a postoperative diagnosis of NIFTP or EFVPTC. A detailed analysis of patients’ medical charts and pathology reports was used to analyze clinicopathological features retrospectively.

Results: The 73-case cohort consisted of 42 NIFTP and 31 IFVPTC cases (median age 54 years, 47 (64 %) women). NIFTP group was consisted of more female sex subjects (P<0,001). The ultrasound findings for NIFTP and minimally invasive EFVPTC typically demonstrated a circumscribed oval/round nodule with a hypoechoic rim. Presence of halo in nodules was significantly more prevalent in the EFVPTC group (P<0.001). 47.6% of the nodules in NIFTP were solid-cystic, 42% solid, and 9.5% cystic. These ratios were similar in EFVPTC (35.5%, 48.4%, and 16.1%, respectively). There were no differences in microcalcification in nodules (P=0.06). Metastatic lymph node(s) was found in 8 cases of EFVPTC but none in NIFTP (P<0.001). In NIFTP, the prevalence of nodules being TIRADS 2, 3, 4, and 5 was 21,4%, 23,8%, 45,2%, 7,1%, respectively. EFVPTC group had more TIRADS-5 nodules (P<0,01). The NIFTP and EFVPTC groups showed benign features, with a majority of the patients categorized as Bethesda category III (39,5 % and 25.8%, respectively) (P<0.02) or IV (28,5% and 30.2%, respectively). Lobectomy has been performed in only 9% (4/42) of NIFTP cases. Total thyroidectomy was the preferred surgical method in remaining NIFTP and all EFVPTC cases. CK19 staining of nodules in EFVPTC was more prevalent (P<0.001). TNM stages of the groups were similar, too. The rates of postoperative hypoparathyroidism were also comparable (P=0.32). During follow-up, no recurrence or metastasis was observed in any case.

Conclusions: These results demonstrate that NIFTP and EFVPTC are clinically and sonographically similar, despite being pathologically recognized by well-defined criteria. In our study, the presence of peripheral halo, irregular margins, and CK 19 staining in pathology were more common in EFVPTC, which may support the preoperative diagnosis.