Histological Study on the Thyroid Tissue Adjoining the Noninvasive Thyroid Follicular Neoplasm With Papillary-Like Nuclear Features, Seeking a Possible Association With Hashimoto’s Thyroiditis

Papillary thyroid carcinoma (PTC) is the most frequent type of thyroid cancer (TC), and advances in ultrasound methods resulted in better and higher detection of this tumor. Thus, the increase in the incidence of PTC is due to the detection of microcarcinomas by ultrasound, as well as partially, due to the increased diagnosis of the encapsulated and/or well-defined non-invasive follicular variant of thyroid papillary carcinoma (NIEFVPTC). Recently, there was a change in the histological classification of NIEFVPTC, currently known as non-invasive follicular thyroid neoplasm with papillary-like features (NIFTP), thus the clinical evidence leads to an excellent prognosis once its a indolent neoplasia, dismissing additional treatments as lymphadenectomy and radioiodotherapy, therefore reducing psychological impact. This study was approved by the ethics and research committee and addressed the analysis and review of histological slides of thyroid neoplasia that currently meet the criteria for NIFTP. Furthermore, the study sought to evaluate the concomitant existence of NIFTP with histological findings consistent with Hashimoto’s Thyroiditis (HT). Underlying studies evoke a possible increase in the imperil of developing PTC when associated with HT. It should be noted that this morphological correlation is poorly described in the literature. Accordingly, a retrospective study was carried out by histological review of 232 cases diagnosed as PTC from total thyroidectomies with cervical lymphadenectomy from 1993 to 2014, previously diagnosed as NIEFVPTC. The histological slides of these cases came from the Surgical Pathology files of the Pathology Department of UNICAMP, Brazil. After histological review, 14 cases reclassified as NIFTP were selected, all referring to female patients, of which 6 presented histological criteria of NIFTP associated with HT. Additionally, a histological and laboratory correlation of the 14 selected cases was performed through the dosages of relevant serum titers of antithyroid antibodies (anti-TPO and TgAb). Out of the 6 patients detected with association of NIFTP and TH, 5 had significant titers above 65IU/ml for anti-TPO and 120IU/ml for TgAb. Additional data from thyroid ultrasonography were collected and showed that cases of NIFTP without association with HT, presented nodules ranging from 1.5 cm to 5.1 cm, predominantly hypoechoic, solid, with regular contours, peripheral vascularization and located predominantly in the right lobe. In conclusion, 14 cases of NIFTP were detected, among 232 cases of PTC, with 6 cases being histologically associated with HT. Of these, 5 cases had laboratory tests with positive antithyroid antibody titers, proving this association, from a clinical point of view. All cases of NIFTP with and without HT association were female, with nodules ranging from 0.3cm to 5.0cm to ultrasound, predominantly in the right lobe.