Abstract
BackgroundAn international group of experts recommended reclassifying non-invasive follicular variant of papillary thyroid cancers (FVPTC) as ‘non-invasive follicular thyroid neoplasm with papillary-like nuclear features’ (NIFTP) in April 2016. The purpose of this study was to establish preoperative clinical, laboratory, ultrasonographic, and cytological variables, which can differentiate NIFTP from FVPTC.MethodsWe conducted a retrospective chart review of consecutive patients from a single institution evaluated between January 2012 and December 2017. 203 adult patients underwent lobectomy or total thyroidectomy for a FVPTC during that period. Each patient’s medical chart was reviewed and information on pre-operative variables was recorded. An expert pathologist reviewed all surgical specimens and reclassified a subset of FVPTC as NIFTP according to the specific criteria.ResultsOverall, 44 patients were included in the NIFTP group and 159 in the non-NIFTP group. Mean age was 50.1 years in the NIFTP group and 50.7 in the non-NIFTP group. Most patients were female (86.4% (38/44) in the NIFTP group vs 79.8% (127/159) in the non-NIFTP group). More patients underwent lobectomy in the NIFTP group (50% (22/44) vs 16.4% (26/159) in the non-NIFTP group, p = < 0.0001). Less patients received radioactive iodine in the NIFTP group (31.8% (14/44) vs 52.2% (83/159) in the non-NIFTP group, p = 0.0177). Preoperative thyroglobulin levels were lower in NIFTP patients (Median 25.55 mcg/L +/− 67.8 vs 76.06 mcg/L +/− 119.8 in Non-NIFTP, p = 0.0104). NIFTP nodules were smaller (Mean size 22.97 mm +/− 12.3 vs 25.88 mm +/− 11.2 for non-NIFTP, p = 0.0448) and more often solid than non-NIFTP (93.2% (41/44) vs 74.8% (119/159) for non-NIFTP, p = 0.0067). 2017 ACR TIRADS nodule category of 1–4 on ultrasound had a negative predictive value and a sensitivity of 100% for NIFTP. ROC Curve Analysis demonstrated that a preoperative thyroglobulin level of 31.3 mcg/L had a sensitivity of 75% and a specificity of 62.5% to differentiate NIFTP from non-NIFTP cancers.ConclusionLower preoperative thyroglobulin levels, smaller nodule size, solid texture and 2017 ACR TIRADS Category of 1–4 are more strongly associated with NIFTP than FVPTC and can favour less invasive surgical options such as lobectomy.
Highlights
Classical-variant papillary thyroid cancer (CVPTC) has been the most prevalent histological subtype of papillary thyroid cancer, several reports have cited a rise in frequency of follicular-variant of PTC (FVPTC) ranging from 9 to 22.5% [1, 2]
The exclusion of nodules with fine needle aspiration (FNA) cytology showing Bethesda I and II was a decision based on the fact that the vast majority of NIFTP nodules are in the intermediate categories, authors wanted to focus on such categories (Bethesda III and higher) in the analysis
Of the 203 patients, 44 (21.7%) patients were included in the NIFTP group and 159 (78.3%) patients were included in the non-NIFTP group (148 minimally invasive encapsulated follicular variant of papillary thyroid cancers (FVPTC) and 11 infiltrative FVPTC)
Summary
Classical-variant papillary thyroid cancer (CVPTC) has been the most prevalent histological subtype of papillary thyroid cancer, several reports have cited a rise in frequency of follicular-variant of PTC (FVPTC) ranging from 9 to 22.5% [1, 2]. A recent multi-institutional study examined 109 patients with non-invasive encapsulated FVPTC and found that none of these patients developed a recurrence, with a followup time varying between 10 and 26 years [3] Based on this indolent clinical course, in April 2016, an international multidisciplinary group of experts recommended reclassifying these tumours as ‘non-invasive follicular thyroid neoplasm with papillary-like nuclear features’ (NIFTP). The purpose of this reclassification was to reduce the clinical and psychological consequences associated with the diagnosis of cancer. An international group of experts recommended reclassifying non-invasive follicular variant of papillary thyroid cancers (FVPTC) as ‘non-invasive follicular thyroid neoplasm with papillary-like nuclear features’ (NIFTP) in April 2016. The purpose of this study was to establish preoperative clinical, laboratory, ultrasonographic, and cytological variables, which can differentiate NIFTP from FVPTC
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