Clinical characteristics of subtypes of follicular variant papillary thyroid carcinoma.

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Clinical characteristics of subtypes of follicular variant papillary thyroid carcinoma.

Thyroid. 2018 Jan 17;:

Authors: Kim MJ, Won JK, Jung KC, Kim JH, Cho SW, Park DJ, Park YJ

Abstract
Background Among follicular variant papillary thyroid carcinomas (FVPTCs), the non-invasive encapsulated subtype has an excellent prognosis. For this reason, re-classification of non-invasive encapsulated FVPTC (EFVPTC) as a new entity called "non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP)" has been proposed, but controversy remains. To characterize non-invasive EFVPTC in an Asian population, we compared the clinicopathological features of each FVPTC subtype in a Korean population. Methods FVPTC patients (n = 142) who underwent thyroidectomy between 2009 and 2014, and whose tumor size was larger than 1 cm, were included in the study. The surgical pathology of each patient was re-evaluated by two independent expert pathologists. Results The percentages of non-invasive and invasive EFVPTC and infiltrative FVPTC (IFVPTC) in the study were 30%, 31%, and 39%, respectively. There was no difference in preoperative cytological diagnosis or the extent of surgery between non-invasive and invasive EFVPTC. However, the proportion of Bethesda category IV was lower in IFVPTC (16%) than in non-invasive and invasive EFVPTC (35% and 36%, respectively). Therefore, thyroid lobectomy was more common in non-invasive or invasive EFVPTC (54% or 48%, respectively) than in IFVPTC (16%). Non-invasive EFVPTC showed lower multiplicity, extrathyroidal extension, and BRAFV600E mutation frequency (three cases, 8%) than did invasive EFVPTC, but other pathological characteristics were similar. However, IFVPTC showed significant differences in tumor size, extrathyroidal extension, lymph node metastasis, TNM stage, and ATA high risk category compared with non-invasive and invasive EFVPTC. In the non-invasive EFVPTC group, there were six cases (14%) with multifocality and three cases (7%) with lymph node metastasis. However, only two cases with multifocality and one case with lymph node metastasis originated from non-invasive FVPTC, while the other cases were from coexisting conventional PTCs. Conclusions Non-invasive EFVPTC has favorable pathological features, but lymph node metastasis or BRAFV600E mutations were observed in some patients. Therefore, in order for the distinction between non-invasive EFVPTC and invasive EFVPTC to have more clinical significance, the criteria for NIFTP needs to be more strictly revised.

PMID: 29343212 [PubMed - as supplied by publisher]

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