A Different Perspective on Evaluating the Malignancy Rate of the Non-Diagnostic Category of the Bethesda System for Reporting Thyroid Cytopathology: A Single Institute Experience and Review of the Literature

<div><p>Objective</p><p>To determine the malignancy rate in the non-diagnostic (ND) category of the Bethesda System for Reporting Thyroid Cytopathology (BSRTC) based on a different approach in relation to histopathology diagnoses.</p><p>Study Design</p><p>All ND fine needle aspirations (FNAs) that were performed under ultrasound guidance by an interventional radiologist with rapid on-site evaluation were included in the study. Slides were reevaluated to identify the cause of inadequacy as “qualitative” or “quantitative.” The malignancy rate of the ND category was assessed. Nodule/patient characteristics were compared between benign and malignant cases within the study cohort.</p><p>Results</p><p>The study cohort consisted of 192 ND aspirations. Overall there were 156 (81.3%) women and 36 (18.7%) men with a mean age of 50.6 years (range 24–82 years). The malignancy rate was 4.7%. None of the nodules (size, consistency, and number) or patient characteristics (gender and age) were found to be predictive of malignancy.</p><p>Conclusion</p><p>The malignancy rate of the ND category was high when compared to BSRTC predictions, but at the low end of the reported malignancy rates in the literature. Our results revealed that cyto-histopathologic correlation and method of malignancy rate estimation could have an effect on a wide range of reported malignancy rates. Furthermore, patient/nodule dependent factors were not statistically found to be predictive of malignancy.</p></div

Patient and nodule characteristics of malignant cases.

<p>Patient and nodule characteristics of malignant cases.</p

Comparison of nodule and patient characteristics in benign and malignant cases.

<p>Comparison of nodule and patient characteristics in benign and malignant cases.</p

Non-diagnostic and malignancy rates for thyroid FNA in the literature.

<p>Non-diagnostic and malignancy rates for thyroid FNA in the literature.</p

Distribution of FNA cases during the study period.

<p>Distribution of FNA cases during the study period.</p

Risk factors for malignancy.

<p>Risk factors for malignancy.</p

Distribution of histopathologic diagnoses.

<p>Distribution of histopathologic diagnoses.</p

Should subcentimeter non-invasive encapsulated, follicular variant of papillary thyroid carcinoma be included in the noninvasive follicular thyroid neoplasm with papillary-like nuclear features category?

Objective: In 2016, non-invasive, well-circumscribed and encapsulated, follicular variant of papillary thyroid carcinoma (NI-EFV PTC) was reclassified as noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) in order to reduce overtreatment of this indolent tumor. However, the study cohort did not include subcentimeter tumors, i.e., papillary thyroid microcarcinoma (mPTC) with NI-EFV morphology, and such lesions are still regarded and staged by most pathologists as microcarcinomas. It is therefore crucial to evaluate the clinical outcome of subcentimeter NI-EFVs. Methods: A total of 52 patients with unifocal mPTC, NI-EFV from five tertiary hospitals who had at least one year clinical follow-up (FU) without post-operative RAI administration were included in the study. A control group of 57 invasive mPTC follicular variant was also included. Results: The median tumor size was 0.44 cm (range 0.1â\u80\u930.9 cm). There were no distant or lymph node metastases at diagnosis in all patients. Twenty-three patients (44%) underwent lobectomy alone, while the remaining received total thyroidectomy. No recurrence was observed in the entire cohort (n = 52) including all 38 patients with at least 2 years of FU (median FU: 6.3 years). Among 25 patients with â\u89¥5 years of FU, none recurred with a median FU of 9.6 years (range 5.2â\u80\u9318.1 years). In contrast, in the control group with invasive mPTC follicular variant, there were 5 (9%) patients with nodal metastasis at presentation and 1 (2%) who displayed nodal recurrence. Conclusion: Papillary thyroid microcarcinoma, NI-EFV, when stringently selected for, lacks metastasis at presentation and follows an extremely indolent clinical course, even when treated conservatively without RAI therapy. Provided stringent inclusion criteria are met, classification of subcentimeter mPTC, NI-EFV as NIFTP should be considered in order to avoid overtreatment of these biologically indolent lesions