Cytopathology of primary sclerosing mucoepidermoid carcinoma with eosinophilia of the thyroid: a multi-institutional case series and review of literature.

INTRODUCTION: Sclerosing Mucoepidermoid Carcinoma with Eosinophilia (SMECE) of the thyroid is an extremely rare tumor that exhibits unique histologic characteristics and is nearly always associated with lymphocytic thyroiditis (LT). However, the cytomorphologic and clinicopathologic characteristics of SMECE have only been described in rare case reports. MATERIALS AND METHODS: Authors' institution laboratory information systems were searched for records of SMECE between 2012 and 2023. Literature review was performed using keywords "Sclerosing mucoepidermoid carcinoma with eosinophilia", "thyroid", and "cytopathology" to search through institution electronic library databases for relevant articles. RESULTS: A total of 19 cases were identified, 3 unpublished in the authors' archives and 16 in the literature which had fine needle aspiration (FNA) material or cytologic features available for review, and were comprised of 3 males and 16 females. The common cytomorphologic characteristics of SMECE included fragments or loose clusters of intermediate-type epidermoid cells in a background of prominent LT and eosinophils. Overt keratinization, mucinous cells, and extracellular mucin were not commonly encountered, resulting in diagnostic challenges, especially if eosinophils associated with epithelial cell clusters were rare. The cases were reported as "Nondiagnostic" (1 case), "Atypia of Undetermined Significance" (4 cases), "Suspicious for Malignancy" (3 case), or "Malignant" (11 cases). CONCLUSIONS: The clinical course of SMECE of the thyroid varied and distinct cytomorphologic characteristics in a subset of patients who experienced aggressive disease raises the possibility of different prognostic grades. Cases with keratinized squamous cells and necrosis mimic anaplastic (undifferentiated) thyroid carcinoma, but the clinical history and radiologic findings can be helpful to exclude this diagnosis.

Validation of targeted next-generation sequencing of cell-free DNA from archival cerebrospinal fluid specimens for the detection of somatic variants in cancer involving the leptomeninges: Cytopathologic and radiographic correlation.

BACKGROUND: Leptomeningeal metastases occur across multiple solid and lymphoid cancers, and patients typically undergo cytopathologic assessment of cerebrospinal fluid (CSF) in this setting. For patients diagnosed with metastatic cancer, the detection of actionable somatic mutations in CSF can provide clinically valuable information for treatment without the need for additional tissue collection. METHODS: The authors validated a targeted next-generation sequencing assay for the detection of somatic variants in cancer (OncoPanel) on cell-free DNA (cfDNA) isolated from archival CSF specimens in a cohort of 25 patients who had undergone molecular testing of a prior tumor specimen. RESULTS: CSF storage time and volume had no impact on cfDNA concentration or mean target coverage of the assay. Previously identified somatic variants in CSF cfDNA were detected in 88%, 50%, and 27% of specimens diagnosed cytologically as positive, suspicious/atypical, and negative for malignancy, respectively. Somatic variants were identified in 81% of CSF specimens from patients who had leptomeningeal enhancement on magnetic resonance imaging compared with 31% from patients without such enhancement. CONCLUSIONS: These data highlight the stability of cfDNA in CSF, which allows for cytopathologic evaluation before triage for next-generation sequencing assays. For a subset of cases in which clinical suspicion is high but cytologic or radiographic studies are inconclusive, the detection of pathogenic somatic variants in CSF cfDNA may aid in the diagnosis of leptomeningeal metastases.

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.

Ultrasound Follow-Up of Benign Thyroid Nodules: A Scoping Review.

Background: For cytologically benign thyroid nodules with very low to intermediate suspicion ultrasound patterns, optimal ultrasound follow-up intervals and outcomes of discontinuing follow-up are unclear. Methods: Ovid MEDLINE, Embase, and Cochrane Central were searched through August 2022 for studies comparing different ultrasound follow-up intervals and discontinuation versus continuation of ultrasound follow-up. The population was patients with cytologically benign thyroid nodules and very low to intermediate suspicion ultrasound patterns, and the primary outcome was missed thyroid cancers. Utilizing a scoping approach, we also included studies that were not restricted to very low to intermediate suspicion ultrasound patterns or evaluated additional outcomes such as thyroid cancer-related mortality rate, nodule growth, and subsequent procedures. Quality assessment was performed, and evidence was synthesized qualitatively. Results: One retrospective cohort study (n = 1254; 1819 nodules) compared different first follow-up ultrasound intervals for cytologically benign thyroid nodules. There was no difference between >4- versus 1- to 2-year intervals to first follow-up ultrasound in the likelihood of malignancy (0.4% [1/223] vs. 0.3% [2/715]), and no cancer-related deaths occurred. Follow-up ultrasound at >4 years was associated with increased likelihood of ≥50% nodule growth (35.0% [78/223] vs. 15.1% [108/715]), repeat fine needle aspiration (19.3% [43/223] vs. 5.6% [40/715]), and thyroidectomy (4.0% [9/223] vs. 0.8% [6/715]). The study did not describe ultrasound patterns or control for confounders, and analyses were based on interval to first follow-up ultrasound only. Other methodological limitations were not controlling for variability in follow-up duration and unclear attrition. The certainty of evidence was very low. No study compared discontinuation of ultrasound follow-up versus continuation. Conclusions: This scoping review found that evidence comparing different ultrasound follow-up intervals in patients with benign thyroid nodules is limited to one observational study, but suggests that the subsequent development of thyroid malignancies is very uncommon regardless of follow-up interval. Longer follow-up may be associated with more repeat biopsies and thyroidectomies, which could be related to more interval nodule growth that meets thresholds for further evaluation. Research is needed to clarify optimal ultrasound follow-up intervals for low to intermediate suspicion cytologically benign thyroid nodules and outcomes of discontinuing ultrasound follow-up for very low suspicion nodules.

Quantifying the hidden impact of COVID-19 pandemic: The cytology perspective.

BACKGROUND: The burden of the COVID-19 pandemic is often enumerated in lives lost, but the strain on health care resources and mobility limitations contributed to the burden of non-COVID related disease. In this study, we evaluated the impact of the pandemic through a time series review of cytology samples. METHODS: Pathology reports for all cytology specimens received from January 2019 through April 2021 at our institution were reviewed. Time series analysis was performed using moving averages, time trend analysis, cross-correlation, and tests of homogeneity. RESULTS: During the first peak of the pandemic (March-June 2020), breakpoint analysis showed a downward shift in the number of gynecologic (-89.4%) and non-gynecologic (-70.4%) cytology specimens within a week of declaration of an emergency. Cross-correlation analysis showed a relationship between sample numbers and COVID-19 cases during the initial phase of the pandemic (April-June 2020). During the second surge (October 2020-April 2021), despite the higher incidence of COVID-19, there was a smaller impact on cytology samples (-20.1% and - 24.8% for gynecologic and non-gynecologic samples, respectively). During the first 3 months of the pandemic, 154 fewer malignant cases were identified compared with the prior year. Although specimen numbers slowly returned to baseline following the first wave of the pandemic, the earlier decline in malignant diagnoses was not offset during the study period. CONCLUSIONS: The deleterious effects of COVID-19 extend beyond direct mortality attributed to the disease. The significant decrease in diagnostic cytology specimens during this period has profound implications including delayed care and missed disease.

Diagnosis of thyroid nodules.

Thyroid nodules are common, usually asymptomatic, and often pose minimal risk to the affected patient. However, 10-15% prove malignant and serve as the rationale for diagnostic assessment. Safely identifying and treating a relevant thyroid cancer through a cost-effective process is the primary goal of the treating practitioner. Ultrasound is the principal means of initial nodule assessment and should be performed when any thyroid nodule is suspected. Fine-needle aspiration provides further cytological determination of benign or malignant disease and is generally applied to nodules larger than 1-2 cm in diameter, on the basis of holistic risk assessment. The Bethesda System for Reporting Thyroid Cytopathology provides standardised terminology, which enhances communication among health-care providers and patients. Benign cytology is highly accurate, whereas indeterminate cytology could benefit from further application of molecular testing. The ultimate goal of diagnostic assessment of thyroid nodules is to accurately identify malignancy while avoiding overtreatment. Low-risk thyroid nodules can be safely monitored in many patients with minimal diagnostic intervention.

Subtype of atypia on cytology and risk of malignancy in pediatric thyroid nodules.

BACKGROUND: Thyroid nodules with atypia of undetermined significance (AUS) are challenging to manage because of their intermediate risk of malignancy. Subclassification of atypia can refine malignancy risk in adult AUS nodules but has not been evaluated in children. METHODS: This was a retrospective cohort study of pediatric patients (<19 years old) who underwent fine-needle aspiration (FNA) of a thyroid nodule with resulting AUS cytology. Atypia was subclassified as nuclear only, architectural only, nuclear and architectural, or oncocytic. The primary outcome was the association between atypia subtype and malignancy. A secondary outcome was the association of atypia subtype with repeat FNA cytology. RESULTS: Sixty-eight AUS nodules in 61 patients were analyzed. The median age at FNA was 16.2 years (range, 9.8-18.9 years). Twenty-four nodules (35%) were malignant. Nuclear atypia only was present in 17 nodules (25%), architectural atypia only was present in 27 nodules (40%), nuclear and architectural atypia was present in 20 nodules (29%), and predominantly oncocytic features were present in 4 nodules (6%). The presence of nuclear atypia was associated with a significantly increased rate of malignancy (22 of 37 [59%] vs 2 of 31 [6.5%]; P < .001), whereas architectural atypia was not associated with malignancy (P = .8). Repeat FNA was performed in 42 of 68 nodules (62%). In nodules with initial nuclear and architectural atypia, benign repeat cytology had a high false-negative rate (3 of 6; 50%). CONCLUSIONS: Pediatric AUS nodules with nuclear atypia have a high rate of malignancy, but architectural atypia is not associated with malignancy. In nodules with nuclear atypia, repeat FNA may inform clinical decisions regarding the need for resection. In the absence of suspicious clinical features, nodules without nuclear atypia might be considered for observation rather than resection or repeat FNA.

Developing dashboards for performance improvement in cytopathology.

INTRODUCTION: Cytopathology has well-defined and objective quality metrics for monitoring the performance of cytopathologists (CPs) and cytotechnologists (CTs). We transformed these metrics into dashboards for real-time visualization and on-demand feedback. METHODS: Dashboards were constructed with data from the previous 10 calendar years using the software Tableau. The dashboards for CPs were designed to display 2 gynecologic metrics and 1 nongynecologic metric: the ASCUS:SIL ratio, the percentage of high-risk human papillomavirus (HPV)-positive ASCUS interpretations (HPV+ ASCUS rate), and the proportion of AUS/FLUS thyroid interpretations. CT dashboards were designed to include these plus 2 others: the percentage of Papanicolaou tests referred for CP review and the percentage of Papanicolaou tests interpreted as unsatisfactory. Established professional benchmarks or standard deviations were used to set color-coded "goal," "borderline," and "attention" zones. RESULTS: Personal dashboards were successfully developed and implemented for CPs and CTs in the laboratory, with results that are automatically updated every week, requiring minimal curation. Each CP and CT has a unique link that allows them access to their results at any time. Color-coded displays show the individual their quality metrics over the past 10 years, with a snapshot of data from the past 3 months. The laboratory director has a unique link that allows the director access to results for each individual and the laboratory in aggregate. CONCLUSIONS: Personalized dashboards enable individuals to access their performance metrics on demand and examine recent performance as well as patterns over time. This facilitates self-motivation to improve performance and adhere to professional benchmarks.

Integration of rare cell capture technology into cytologic evaluation of cerebrospinal fluid specimens from patients with solid tumors and suspected leptomeningeal metastasis.

INTRODUCTION: Dissemination of tumor to the leptomeninges, subarachnoid space, and cerebrospinal fluid (CSF) is termed leptomeningeal metastasis (LM) and occurs in approximately 5% of patients with solid tumors. LM is associated with dismal clinical prognosis, and routine cytologic and radiologic methods for diagnosing LM have limited sensitivity. The CellSearch immunomagnetic rare cell capture assay is FDA-approved to detect circulating tumor cells (CTCs) in peripheral blood, but whether it may have a role in identifying CSF CTCs is still unclear. MATERIAL AND METHODS: CSF specimens from 20 patients with clinically suspected solid tumor LM collected from 2 institutions between October 2016 and January 2019 were evaluated with routine CSF cytology and underwent concurrent CTC testing with the CellSearch assay (Menarini-Silicon Biosystems, Huntingdon Valley, PA). The results of CTC testing were compared to routine CSF cytology and radiologic studies for detecting LM. RESULTS: The CellSearch assay achieved a sensitivity of 88.9% and specificity of 100% for detecting LM (using a threshold of 1 CTC/mL of CSF as the definition of a positive CTC result). One patient with negative CSF cytology but positive CTCs developed positive cytology 37 days later. CONCLUSIONS: In this proof-of-principle pilot study, we demonstrate that the CellSearch assay can be successfully integrated with the routine CSF cytologic workflow to aid in the diagnosis of solid tumor LM. Importantly, CTCs detected by this rare cell capture assay are found in a subset of patients with non-positive routine CSF cytology, which may have significant implications for patient management.

Defining thyroid spherules: A benign cytomorphologic feature that mimics microfollicles.

BACKGROUND: Distinctive rounded structures termed spherules have been observed in thyroid fine-needle aspiration (FNA) samples. Although they are often small and interpreted as microfollicles, spherules are notable for the even spacing of the follicular cells along the perimeter of the structure. Because they have an orderly architectural arrangement, it has been hypothesized that spherules are benign and do not carry the same risk of malignancy that traditional microfollicles do. The aim of this study was to identify the clinical significance and histopathologic correlate of spherules. METHODS: Thyroid FNAs (n = 637) with an interpretation of atypia of undetermined significance (AUS) were reviewed for the presence of spherules, which were defined as small follicles with a rounded, smooth, sharply defined outer contour, evenly spaced nuclei, and a 3-dimensional appearance. Cases were included if spherules accounted for >50% of follicular cell arrangements. Clinical, histopathologic, molecular, and sonographic follow-up data were obtained. RESULTS: Twenty-five spherule cases were identified, and they represented 3.9% of all AUS cases reviewed. All 24 cases with follow-up had a benign outcome. Eleven were tested with the Afirma gene expression classifier; 8 were benign according to the gene expression classifier, and 3 were suspicious but histologically benign after surgical resection. Four additional cases were histologically benign after surgery. Five patients had repeat benign cytology. Four patients had repeat stable ultrasound findings. CONCLUSIONS: Thyroid nodules diagnosed as AUS, if composed predominantly of spherules, are associated with a benign outcome. Recognizing this distinctive cytomorphologic finding may help to reduce the number of FNAs interpreted as AUS and save patients from unnecessary additional testing and surgery.

Analytical and Clinical Validation of Expressed Variants and Fusions From the Whole Transcriptome of Thyroid FNA Samples.

Introduction: The Afirma® Xpression Atlas (XA) detects gene variants and fusions in thyroid nodule FNA samples from a curated panel of 511 genes using whole-transcriptome RNA-sequencing. Its intended use is among cytologically indeterminate nodules that are Afirma GSC suspicious, Bethesda V/VI nodules, or known thyroid metastases. Here we report its analytical and clinical validation. Methods: DNA and RNA were purified from the same sample across 943 blinded FNAs and compared by multiple methodologies, including whole-transcriptome RNA-seq, targeted RNA-seq, and targeted DNA-seq. An additional 695 blinded FNAs were used to define performance for fusions between whole-transcriptome RNA-seq and targeted RNA-seq. We quantified the reproducibility of the whole-transcriptome RNA-seq assay across laboratories and reagent lots. Finally, variants and fusions were compared to histopathology results. Results: Of variants detected in DNA at 5 or 20% variant allele frequency, 74 and 88% were also detected by XA, respectively. XA variant detection was 89% when compared to an alternative RNA-based detection method. Low levels of expression of the DNA allele carrying the variant, compared with the wild-type allele, was found in some variants not detected by XA. 82% of gene fusions detected in a targeted RNA fusion assay were detected by XA. Conversely, nearly all variants or fusions detected by XA were confirmed by an alternative method. Analytical validation studies demonstrated high intra-plate reproducibility (89%-94%), inter-plate reproducibility (86-91%), and inter-lab accuracy (90%). Multiple variants and fusions previously described across the spectrum of thyroid cancers were identified by XA, including some with approved or investigational targeted therapies. Among 190 Bethesda III/IV nodules, the sensitivity of XA as a standalone test was 49%. Conclusion: When the Afirma Genomic Sequencing Classifier (GSC) is used first among Bethesda III/IV nodules as a rule-out test, XA supplements genomic insight among those that are GSC suspicious. Our data clinically and analytically validate XA for use among GSC suspicious, or Bethesda V/VI nodules. Genomic information provided by XA may inform clinical decision-making with precision medicine insights across a broad range of FNA sample types encountered in the care of patients with thyroid nodules and thyroid cancer.

A Cohort Analysis of Clinical and Ultrasound Variables Predicting Cancer Risk in 20,001 Consecutive Thyroid Nodules.

CONTEXT: Assessing thyroid nodules for malignancy is complex. The impact of patient and nodule factors on cancer evaluation is uncertain. OBJECTIVES: To determine precise estimates of cancer risk associated with clinical and sonographic variables obtained during thyroid nodule assessment. DESIGN: Analysis of consecutive adult patients evaluated with ultrasound-guided fine-needle aspiration for a thyroid nodule ≥1 cm between 1995 and 2017. Demographics, nodule sonographic appearance, and pathologic findings were collected. MAIN OUTCOME MEASURES: Estimated risk for thyroid nodule malignancy for patient and sonographic variables using mixed-effect logistic regression. RESULTS: In 9967 patients [84% women, median age 53 years (range 18 to 95)], thyroid cancer was confirmed in 1974 of 20,001 thyroid nodules (9.9%). Significant ORs for malignancy were demonstrated for patient age <52 years [OR: 1.82, 95% CI (1.63 to 2.05), P < 0.0001], male sex [OR: 1.68 (1.45 to 1.93), P < 0.0001], nodule size [OR: 1.30 (1.14 to 1.49) for 20 to 19 mm, OR: 1.59 (1.34 to 1.88) for 30 to 39 mm, and OR: 1.71 (1.43 to 2.04) for ≥40 mm compared with 10 to 19 mm, P < 0.0001 for all], cystic content [OR: 0.43 (0.37 to 0.50) for 25% to 75% cystic and OR: 0.21 (0.15 to 0.28) for >75% compared with predominantly solid, P < 0.0001 for both], and the presence of additional nodules ≥1 cm [OR: 0.69 (0.60 to 0.79) for two nodules, OR: 0.41 (0.34 to 0.49) for three nodules, and OR: 0.19 (0.16 to 0.22) for greater than or equal to four nodules compared with one nodule, P < 0.0001 for all]. A free online calculator was constructed to provide malignancy-risk estimates based on these variables. CONCLUSIONS: Patient and nodule characteristics enable more precise thyroid nodule risk assessment. These variables are obtained during routine initial thyroid nodule evaluation and provide new insights into individualized thyroid nodule care.

Differences in Thyroid Nodule Cytology and Malignancy Risk Between Children and Adults.

Background: The Bethesda System for Reporting Thyroid Cytopathology (BSRTC) is used to interpret fine-needle aspiration (FNA) cytology of thyroid nodules in children and adults. Nodule management is guided by the implied malignancy risk of each cytological category, which has been derived from adult populations. Whether these implied risks are applicable to pediatric thyroid nodules remains uncertain. We compared malignancy rates between pediatric and adult thyroid nodules within each cytological category. Methods: We evaluated consecutive thyroid nodules ≥1 cm that underwent FNA at the Boston Children's Hospital and Brigham and Women's Hospital from 1998 to 2016. All cytology was interpreted by a single cytopathology group according to the BSRTC. Malignancy rates were compared between pediatric (<19 years) and adult (≥19 years) patients. Results: Four hundred thirty pediatric thyroid nodules and 13,415 adult nodules were analyzed. Pediatric nodules were more likely to be malignant than adult nodules (19% vs. 12%, p = 0.0002). Within cytological categories, malignancy rates were higher in pediatric nodules than in adult nodules that were cytologically nondiagnostic (11% vs. 4%, p = 0.03), atypia of undetermined significance (AUS; 44% vs. 22%, p = 0.004), or suspicious for follicular neoplasm (SFN; 71% vs. 28%, p = 0.001). There were no significant differences between children and adults in the types of thyroid cancers diagnosed in these cytological categories. Among cytologically benign nodules, the difference in malignancy rates was statistically significant but clinically minimal (0.7% vs. 1%, p = 0.001). Malignancy rates did not differ between children and adults among nodules with cytology suspicious for papillary carcinoma (73% vs. 68%, p = 0.67) or positive for malignancy (97% vs. 95%, p = 1). Among the subset of nodules that were resected, the malignancy rate was higher in children than in adults only in nodules that were SFN (71% vs. 36%, p = 0.007). Conclusions: Among thyroid nodules that are cytologically AUS, SFN, or nondiagnostic, malignancy rates are higher in children than in adults. These discrepancies likely represent true differences in malignancy risk between pediatric and adult patients, rather than differences in cytological interpretation. Our findings provide pediatric-specific data to inform the optimal management of thyroid nodules in children, which may differ from that of adult nodules with equivalent cytology.

The Impact of Hashimoto Thyroiditis on Thyroid Nodule Cytology and Risk of Thyroid Cancer.

CONTEXT: The impact of Hashimoto thyroiditis (HT) on the risk of thyroid cancer and its accurate detection remains unclear. The presence of a chronic lymphocytic infiltration imparts a logical mechanism potentially altering neoplastic transformation, while also influencing the accuracy of diagnostic evaluation. METHODS: We performed a prospective, cohort analysis of 9851 consecutive patients with 21,397 nodules ≥1 cm who underwent nodule evaluation between 1995 and 2017. The definition of HT included (i) elevated thyroid peroxidase antibody (TPOAb) level and/or (ii) findings of diffuse heterogeneity on ultrasound, and/or (iii) the finding of diffuse lymphocytic thyroiditis on histopathology. The impact of HT on the distribution of cytology and, ultimately, on malignancy risk was determined. RESULTS: A total of 2651 patients (27%) were diagnosed with HT, and 3895 HT nodules and 10,168 non-HT nodules were biopsied. The prevalence of indeterminate and malignant cytology was higher in the HT vs non-HT group (indeterminate: 26.3% vs 21.8%, respectively, P < 0.001; malignant: 10.0% vs 6.4%, respectively, P < 0.001). Ultimately, the risk of any nodule proving malignant was significantly elevated in the setting of HT (relative risk, 1.6; 95% CI, 1.44 to 1.79; P < 0.001), and was maintained when patients with solitary or multiple nodules were analyzed separately (HT vs non-HT: 24.5% vs 16.3% solitary; 22.1% vs 15.4% multinodular; P < 0.01). CONCLUSION: HT increases the risk of thyroid malignancy in any patient presenting for nodule evaluation. Diffuse sonographic heterogeneity and/or TPOAb positivity should be used for risk assessment at time of evaluation.

Independent Comparison of the Afirma Genomic Sequencing Classifier and Gene Expression Classifier for Cytologically Indeterminate Thyroid Nodules.

Background: For thyroid nodules with indeterminate cytology, the Afirma Gene Expression Classifier (GEC) identified benign nodules to reduce diagnostic surgery, though many nodules classified as suspicious still proved histopathologically benign. The current Afirma Genomic Sequencing Classifier (GSC) demonstrates improved specificity, suggesting more nodules will have a benign result (benign call rate [BCR]), but independent data are needed to confirm this in clinical practice. Methods: Retrospective analysis was performed of all Bethesda III or IV cytology thyroid nodules ≥1 cm tested with GEC (between January 1, 2011, and July 19, 2017) or GSC (between July 20, 2017, and August 27, 2018) at the authors' institution. Afirma testing was not performed reflectively for all nodules with Bethesda III or IV cytology, but rather was applied based on physician-patient decision making. Demographic, sonographic, and cytologic data were collected. The BCR for GEC- versus GSC-tested nodules was compared and further stratified by Bethesda classifications. Results: The study evaluated 600 nodules in 563 patients tested with either GEC (n = 486) or GSC (n = 114). The BCR was 233/486 (47.9%) for the GEC compared to 75/114 (65.8%) for the GSC (p = 0.0006). Hürthle-cell cytology was present in 99/486 (20.4%) nodules in the GEC group compared to 31/114 (27.2%) nodules in the GSC group (p = 0.28). The GSC BCR was significantly higher than the GEC BCR for Bethesda III nodules characterized by Hürthle cells (p = 0.006), but the BCRs were similar for nodules with architectural or cytologic atypia. In Bethesda IV nodules suspicious for follicular neoplasm, BCR for the GEC and GSC were similar (p = 0.68), but for cytology suspicious for Hürthle-cell neoplasm, the GSC BCR was 68.2% (15/22) compared to the GEC BCR of 16.4% (10/61; p < 0.0001). Positive predictive value in resected nodules with a suspicious result was 16/32 (50%) for GSC nodules and 75/221 (33.9%) for GEC nodules (p = 0.1). Conclusions: The higher BCR for the GSC compared to the GEC for indeterminate thyroid nodules, predominantly among nodules with Hürthle-cell cytology, will likely lead to further reduction in surgical management.