Despite the fact that the intracapsulated follicular variant of papillary thyroid cancer (IFVR) progresses very slowly, most patients are treated as patients with conventional thyroid cancer.
The purpose of this study was to review the diagnostic criteria for IFVR and describe its main biological and clinical characteristics.
A retrospective analysis included 109 patients with non-invasive IFVR observed for 10-26 years, and 101 patients with invasive IFVR observed for 1-18 years.
The analysis used a multidisciplinary approach involving 24 international experts of pathologists specializing in endocrinology. The end points of the study were: mortality, the development of metastases, relapse of the disease.
All 109 patients with non-invasive IFVR (67 used only lobectomy, 9 received radioiodine therapy) were alive at the end of the observation period (13 years on average).
Adverse events were diagnosed in 12 of 101 patients with invasive IFVR (12%), including 5 cases with distant metastases, 2 cases of fatal outcome.
Based on an analysis of all cases of thyroid cancer, experts suggested reclassifying the non-invasive intracapsulated follicular variant of papillary thyroid cancer into non-invasive follicular thyroid neoplasia with papillary-like changes.