Pre-operative features of non-invasive follicular thyroid neoplasms with papillary-like nuclear features: An analysis of their cytological, Gene Expression Classifier and sonographic findings.

OBJECTIVE

To investigate the corresponding cytological diagnoses, Gene Expression Classifier (GEC) results and ultrasound features of thyroid nodules diagnosed as non-invasive follicular thyroid neoplasms with papillary-like nuclear features (NIFTP), as well as any coexisting pathology.

METHODS

We performed a retrospective review of thyroid nodules histologically diagnosed as NIFTP at our institution between 1st April 2016 and 1st April 2017. The following data points were collected: demographics, nodule size, ultrasound features, cytological diagnosis, GEC results, origin of sample (in-house vs outside hospital) and any additional pathology identified in the resection specimen.

RESULTS

The case cohort included 87 nodules diagnosed as NIFTP (size range: 1-7 cm, mean: 2.5 cm) from 82 patients (age range: 22-82, mean age: 50.4, M:F-1:4.1). Corresponding FNA results were available for 72 nodules (82.8%) and were categorised as follows: benign (n = 5, 6.9%), atypia of unknown significance/follicular lesion of undetermined significance (n = 29, 40.3%), follicular neoplasm/suspicious for follicular neoplasm/follicular neoplasm with oncocytic features (n = 27, 37.5%), suspicious for papillary thyroid carcinoma (n = 6, 8.3%) and malignant (n = 5, 6.9%). GEC results were available for 32 (44.4%) nodules, with the majority of cases classified as suspicious (81.3%). On ultrasound, most of the nodules were predominantly solid (81.8%), vascular (93.8%), non-calcified (86.5%), and either hypoechoic (44.9%) or isoechoic (38.8%). In addition to NIFTP and other benign findings in the background thyroid, 75 separate malignant tumours were identified in 38 (46.3%) patients, many of which were papillary thyroid microcarcinomas (86.5%) with lymph node metastases present in two cases.

CONCLUSIONS

The majority of thyroid nodules histologically diagnosed as NIFTP have indeterminate cytology (77.8%) and are classified as suspicious (81.3%) by GEC testing. Taken together, these findings can guide clinicians toward a more conservative therapeutic approach.