Follicular Variant of Papillary Thyroid Carcinoma is a Unique Clinical Entity: A Population-Based Study of 10,740 Cases

Abstract

Background: Follicular variant of papillary thyroid carcinoma (FV-PTC) has been increasingly diagnosed in recent years. However, little is known about its clinical behavior. The purpose of this study was to determine the disease characteristics of FV-PTC, and to compare it with classical papillary thyroid carcinoma (C-PTC) and follicular thyroid carcinoma (FTC). Methods: All cases of C-PTC, FV-PTC, and FTC larger than 1 cm in the Surveillance, Epidemiology and End Results (SEER) Cancer Database from 1988 to 2007 were identified. Tumor behavior and patient survival were compared among these three groups. Different risk factors for disease-specific mortality in each group were evaluated by multivariate analysis. Results: More than 36,000 surgical cases were identified, including 21,796 C-PTCs, 10,740 FV-PTCs, and 3958 FTCs. Extrathyroidal extension and lymph-node metastases were more common in FV-PTC than in FTC, but significantly less common than in C-PTC ( p < 0.0001). Distant metastasis rates were present in 2% of patients with FV-PTC, in 1% with C-PTC, and in 4% with FTC ( p < 0.0001). The 10-year disease-specific survival for patients with FV-PTC was 98%, similar to C-PTC (97%) but better than FTC (94%, p < 0.0001). Being over the age of 45 years remained a strong risk factor for disease-specific mortality in both FV-PTC and C-PTC, while the presence of extrathyroidal extension and distant metastases were stronger predictors of disease-specific mortality in FV-PTC than in C-PTC. Conclusions: FV-PTC is a common variant of PTC. Its clinical behavior is unique and represents an intermediate entity with clinical features that are between C-PTC and FTC. Interestingly, despite the variations in clinical behavior, the long-term outcome of these patients remains excellent and similar to C-PTC.

TRAP1 regulates cell cycle and apoptosis in thyroid carcinoma cells

“…FV-PTCs are characterized by a more aggressive behavior compared with classical PTCs (Vivero et al 2013, Yu et al 2013, as well as PDTCs are aggressive tumors with poor prognosis and lack of response to radioiodine (Patel & Shaha 2014). Consistently, a progressive and statistically significant increase of tumor size and tumor stage was observed from PTCs to FV-PTCs, PDTCs and ATCs (P < 0.0001 for both variables; Table 1) in our series of 86 TCs.…”

“…Remarkably, TRAP1 expression is induced along tumor (de)differentiation: (i) in microfollicular compared with macrofollicular areas of normal thyroid gland, (ii) in well-differentiated TCs compared with normal tissues, and (iii) in the transition from well-differentiated to PDTCs and in FV-PTCs, two tumor entities with worst biological and clinical phenotypes compared with well-differentiated TCs (Vivero et al 2013, Yu et al 2013, Patel & Shaha 2014. Consistently, in vitro experiments suggest that TRAP1 is involved in the regulation of cell cycle progression and the apoptotic …”

Angiogenic and lymphangiogenic profiles in histological variants of papillary thyroid carcinoma

“…Some studies demonstrated that FV -PTC differs from CV -PTC both in morphological and clinical aspects. 44,45 The present study provides evidence that FV -PTC has higher LVD compared with MVD. In contrast, there was no difference between LVD and MVD in CV -PTC.…”

The Impact of Noninvasive Follicular Variant of Papillary Thyroid Carcinoma on Rates of Malignancy for Fine-Needle Aspiration Diagnostic Categories

“…Not only has there been an increase in PTC in recent decades, but there has been an increase in the percentage of PTCs that are FVPTC (12 (13) found that there were approaching 22,000 classical type PTCs, 11,000 FVPTCs, and 4000 FTCs. When they compared the behavior of the three groups, they found that extrathyroidal extension and lymph node metastases were more common in FVPTC than in FTC, but significantly less frequent than in classical type PTC.…”