Abstract：
This multi-institutional study investigated non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) frequency and its diagnostic significance in Japan. We reviewed 4008 thyroid nodules resected in six institutions before NIFTP was proposed. Overall, 26 cases diagnosed as non-invasive encapsulated follicular variant of papillary thyroid carcinoma (PTC) and 145 cases of follicular thyroid adenoma (FTA) were included. Of these nodules, 80.8% and 31.0%, respectively, were NIFTPs. In five institutions, NIFTPs were more commonly found in FTA than in PTC nodules. When NIFTP was included with PTC, the overall prevalence was 2.3%, with rates in five institutions below 5.0% (0.8%-4.4%). One NIFTP case with nuclear score 3 revealed nodal metastasis 2.5 years post-resection, and the carcinoma cells were immunohistochemically positive for BRAF. FTAs or NIFTPs with nuclear score 2 did not metastasize. NIFTP was more common among FTA than among PTC nodules, possibly due to underdiagnosis of PTC on nuclear findings. Considering the clinical findings, molecular pathogenesis, and therapeutic strategy in Japan, NIFTP with nuclear score 2 is not different from FTA, and use of this entity terminology is not meaningful. In contrast, NIFTP with nuclear score 3 has potential for metastasis and BRAFV600E mutation. Therefore, in NIFTP cases, nuclear scores 2 and 3 should be separately reported.
摘要：
这项多机构研究调查了日本具有乳头状核特征（NIFTP）频率的非侵入性滤泡性甲状腺肿瘤及其诊断意义。我们回顾了在提出NIFTP之前在六个机构切除的4008个甲状腺结节。总的来说,纳入26例诊断为非侵袭性包膜型甲状腺乳头状癌（PTC）和145例滤泡性甲状腺腺瘤（FTA）。在这些结节中，80.8%和31.0%，分别,是NIFTP。在五个机构中，NIFTP在FTA中比在PTC结核中更常见。当PTC包含NIFTP时，总体患病率为2.3%,五家机构的利率低于5.0%（0.8%-4.4%）。1例核评分为3的NIFTP病例在切除后2.5年显示淋巴结转移，癌细胞BRAF免疫组化阳性。核评分为2的FTA或NIFTP没有转移。NIFTP在FTA中比在PTC结核中更常见，可能是由于PTC在核发现上的诊断不足。考虑到临床发现，分子发病机制，和日本的治疗策略，核评分为2的NIFTP与FTA没有什么不同，和使用这个实体术语是没有意义的。相比之下,核评分为3的NIFTP具有转移和BRAFV600E突变的潜力。因此,在NIFTP病例中，核得分2和3应分别报告。
