Endocrine Abstracts

Introduction: Follicular Thyroid Carcinomas (FTCs) and Follicular Variant Papillary Thyroid Carcinomas (FVPTCs) may present absence of suspicious ultrasonography features more frequently than classic papillary carcinomas. Thus, some cases may be identified with the pattern of ‘low suspicion’ rather than intermediate or high suspicion defined in the American Thyroid Association (ATA) guidelines of 2015. These guidelines establish a size cutoff of 1.5 cm to recommend fine-needle aspiration in nodules belonging to this category of low suspicion, justified because the probability of distant metastasis in FTCs <2 cm is rare. The aim of this study is to analyze the perithyroidal extension and the presence of variables associated with greater aggressiveness in cases of FTC and FVPTC as a function of the initial size.

Description of methods: A retrospective study of 76 patients with diagnosis of FTC or FVPTC was conducted. The presence of the followings clinical and histological parameters were evaluated: initial perithyroidal extension; aggressive histologic variants (extensive capsular invasion, oncocytic features, undifferentiated foci); presence of vascular invasion, presence of lymph node metastases and distant metastases at diagnosis and during follow-up. The differences between the 2 groups were analysed according to nodular size: <1.5 cm (group A) and ≥ 1.5 cm (group B).

Results: 76 cases with a mean age of 53±16 years, 75% women. Group A: 40 cases, size 0.72±0.34 cm, 8% FTC and 92% FVPTC. Group B: 36 cases, size 2.76±1.04 cm, 33% FTC and 67% FVPTC. Extrathyroidal extension 5% vs 19.4% (p0,052); aggressive histologic variants 0% vs 22.2% (P0.002); vascular invasion 0% vs 19.4% (P0.003), lymph node metastases 10% vs 13.9% (P0.6); distant metastasis 0% vs 2.3% (P0.28).

Conclusion: The presence of aggressive histologic variants and vascular invasion was significantly greater in the carcinomas ≥1.5 cm. None of the carcinomas <1.5 cm presented aggressive histological, vascular invasion or distant metastases at diagnosis or during follow-up. Our data agree with the recommendation established by the ATA to choose a size cutoff of 1.5 cm for low suspicion pattern nodules.