The evolution of "atypia" in thyroid fine-needle aspiration specimens

Two-tier subclassification of the Bethesda category III (atypia of undetermined significance/follicular lesion of undetermined significance) in thyroid cytology

BACKGROUND

The Bethesda category III, AUS/FLUS, comprises a heterogeneous group of thyroid lesions with variable risk of malignancy (ROM). This study evaluates ROM in two subgroups of this category based on nuclear atypia and architectural atypia.

METHODS

Cases in Bethesda category III were reported based on nuclear atypia (AUS) and architectural atypia (FLUS). ROM was calculated by comparing the cytologic diagnosis to the follow-up histologic diagnosis.

RESULTS

Among the 610 Bethesda category III cases in this study, 306 (50.2%) and 304 (49.8%) cases were reported as AUS and FLUS, respectively. One hundred and eighty six of 306 AUS (60.8%) and 193 of 304 FLUS (63.5%) cases underwent surgical intervention. ROM of the cases in Bethesda category III was 12.8% if all cases were counted and 20.6% if only surgical cases were counted. When analyzing separately, ROM of AUS cases was 17.0% and 28.0% with all cases and surgical cases only, respectively. For FLUS cases, ROM was 8.6% and 13.5% with all cases and surgical cases only, respectively.

CONCLUSION

In Bethesda category III, ROM in the cases with nuclear atypia was significantly higher than the cases with architectural atypia. Sub-classifying the Bethesda Category III cases with nuclear atypia and architectural atypia, respectively may better stratify the ROM.

Autoimmune Thyroid Disease and Differentiated Thyroid Carcinoma: A Review of the Mechanisms That Explain an Intriguing and Exciting Relationship

Autoimmune thyroid disease is a complex and highly frequent disease, where a wide variety of genetic, epigenetic and environmental factors (among others) come together and interact, and is characterized by the presence of two clinical outcomes: hypothyroidism (in Hashimoto's thyroiditis) and hyperthyroidism (in Graves-Basedow disease). For its part, differentiated thyroid carcinoma (mainly papillary carcinoma) is the most common type of cancer affecting the thyroid (and one of the most prevalent worldwide). An important co-occurrence between autoimmune thyroid disease and differentiated thyroid carcinoma has been documented. In this article, studies that have evaluated possible associations and relationships between autoimmune thyroid disease and differentiated thyroid cancer are systematically described and summarized. To date, the underlying mechanism that explains this association is inflammation; however, the characteristics and designs of the studies evaluated do not yet allow a causal relationship between the two entities to be established. These aspects have made it difficult to establish "causality" in the continuum of the pathogenesis between both conditions.

Binary subclassification scheme (AUS-Nuclear versus AUS-Other) adequately risk-stratifies thyroid fine needle aspiration specimens classified as Atypia of Undetermined Significance

INTRODUCTION

The Bethesda System for Reporting Thyroid Cytopathology previously described 4 subclasses of atypia within the Atypia of Undetermined Significance (AUS) category: nuclear (AUS-Nuc), architectural (AUS-A), oncocytic (AUS-Onc), and atypia not otherwise specified (AUS-NOS). Accumulating evidence supports a binary AUS subclassification scheme based primarily on the presence of nuclear atypia only. The purpose of this study is to compare the risk stratification of binary versus 4-tier AUS subclassification systems among AUS nodules with molecular and/or histologic follow-up.

MATERIALS AND METHODS

Thyroid aspirates classified as AUS and tested using Afirma (Veracyte, Inc.) between 6/2013 and 7/2021 were included. For resected nodules, histological classification was considered as the final outcome. For unresected nodules, benign Afirma results were considered low-risk outcomes, similar to histologically benign nodules. Suspicious or nondiagnostic Afirma results were considered indeterminate outcomes. The prevalence of outcomes warranting surgery (noninvasive follicular thyroid neoplasm with papillary-like nuclear features [NIFTP] or cancer) was calculated for each AUS subclass.

RESULTS

A total of 559 AUS nodules with Afirma testing were identified. Excluding nodules with indeterminate molecular outcomes, NIFTP/cancer prevalence for AUS-Nuc was 21% (57/266), which was higher than that for AUS-A (6%, 11/188), AUS-Onc (8%, 4/53), and AUS-NOS (0%, 0/9). A binary AUS subclassification scheme based on nuclear atypia showed a significant difference in NIFTP/cancer prevalence (21% versus 6%, P < 0.0001).

CONCLUSIONS

Binary reporting of AUS subclasses based on nuclear atypia distinguishes cases with a higher risk of NIFTP/cancer. There is a low but non-negligible prevalence of NIFTP/cancer in cases without nuclear atypia.

Diagnostic Value and Challenges of BRAF V600E Molecular Testing and Thyroid Fine-Needle Aspiration Cytology: A Retrospective Study from a Tertiary Institution in Southern Hunan Province, China

INTRODUCTION

Combined thyroid fine-needle aspiration (FNA) cytology and valine-to-glutamate substitution at codon 600 of B-Raf proto-oncogene, serine/threonine kinase (BRAF V600E) mutation detection are procedures used for diagnosing thyroid nodules in many Chinese tertiary institutions. This retrospective study at our institution aimed to explore the effectiveness and challenges of the combined approach in diagnosing thyroid nodules and the correlation between BRAF V600E mutation status and behavior of papillary thyroid carcinoma.

METHODS

Thyroid FNA cytology and BRAF V600E mutation detection results were reviewed between November 2020 and July 2022. A total of 623 patients, each of whom underwent thyroidectomy and final pathological examination after FNA cytology diagnosis, were included in the study. The relationship between the BRAF V600E mutational status and pathological parameters was analyzed using the χ2 test. The effectiveness and challenges of FNA cytology alone and the combined procedure were also evaluated based on the final pathology.

RESULTS

Of 623 patients, 591 were diagnosed with papillary thyroid carcinoma (PTC), of which 456 were positive for the BRAF V600E mutation. It demonstrated near-perfect specificity for identifying PTC, and its incidence rate showed an age-specific curve with an inverted U-shaped distribution. The final pathological examination showed that the combined procedure had a higher sensitivity (83.91%) than FNA cytology alone (63.45%) for distinguishing PTC from other lesions (p < 0.001). Mutational status was associated with a larger maximum tumor diameter (p = 0.003) and a tendency of capsular invasion (p = 0.0542) but possibly unrelated to central lymph node metastasis (p = 0.1846). Nodular goiters accounted for most benign entities initially designated as Bethesda categories III-V.

CONCLUSION

BRAF V600E mutational analysis complements cytopathology and improves the PTC detection rate in FNA cytology samples due to the high prevalence of the mutation in China. BRAF V600E mutation does not show a statistical correlation with tumor aggressiveness. Morphological pitfalls such as histocyte aggregation, cystic-lining cells in nodular goiters, and oncocytes in Hashimoto's thyroiditis, were overwhelmingly found in BRAF V600E-negative specimens.

Degenerative atypia in benign thyroid nodules: a potential diagnostic pitfall on fine-needle aspiration

INTRODUCTION

Benign (B) follicular lesions of the thyroid are among the most encountered specimens on fine needle aspiration (FNA). Although FNA and The Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) remain highly accurate, minimally invasive and robust tools in triaging thyroid nodules, false positive (FP) diagnoses may still occur. Endocrine-type degenerative atypia can cause diagnoses of suspicious for malignancy (SFM) or malignant (M), resulting in overtreatment and exposure to undue surgical risk in patients.

MATERIALS AND METHODS

We performed a multi-institutional retrospective clinicopathologic correlation of benign thyroid nodules with degenerative atypia on FNA. Review of cytologic material was conducted to identify potential cytomorphologic features which may have prompted these diagnoses.

RESULTS

Among 342 patients with benign thyroid nodules harboring degenerative atypia, 123 had available preceding FNA cytopathology. TBSRTC nondiagnostic, B, atypia of undetermined significance, follicular neoplasm, SFM, and M, comprised 3.3%, 49.6%, 30.1%, 13.0%, 2.4%, and 1.6% of cases. Among patients with FP diagnoses (SFM and M), 100% underwent total thyroidectomy, and 40.0% underwent additional neck lymph node dissections. Among remaining patients, 61.0%, 39.0%, and 0% underwent lobectomy, thyroidectomy, and lymph node dissection. The number of patients who underwent total thyroidectomy was significantly different (P = 0.03) between those with FP nodules and those without.

CONCLUSIONS

We demonstrate that 4.1% of nodules harboring endocrine-type degenerative atypia may be given FP diagnoses on initial FNA. Such atypia may be indistinguishable from that of Graves' Disease, dyshormonogenic goiter, and radiation therapy. FP diagnoses of degenerative atypia can expose patients to undue surgical procedures and risks.