Evaluation of grade in a genotyped cohort of sporadic medullary thyroid carcinomas

AIMS

Tumour grade and RET mutation status, especially the presence of high-risk exon 15 and 16 RET mutations, have been reported to be prognostic in patients with sporadic medullary thyroid carcinoma (MTC). The aims of our study were to evaluate the performance of two recently proposed grading systems and to assess the association between grade and genotype in a cohort of sporadic MTCs.

METHODS AND RESULTS

We identified 44 sporadic MTCs. All available tumour slides were examined, and cases were assigned a grade on the basis of either mitotic count and tumour necrosis, or mitotic count, tumour necrosis, and Ki-67 proliferative index, as described in two recent studies. Additional clinicopathological features and outcome information were obtained from the pathology reports and electronic medical records. The presence of RET and RAS mutations was determined either with direct sequencing or with massively parallel sequencing. Both grading systems were prognostic for progression-free survival and disease-specific survival on univariate analysis. There was no correlation between grade and mutation status. Specifically, neither RET nor high-risk RET mutations were enriched in high-grade tumours, as assessed by either grading scheme.

CONCLUSION

Our findings suggest that grade is not correlated with RET/RAS mutation status, indicating that grade and genotype may give independent prognostic information.

Oncogenic Mutations in PI3K/AKT/mTOR Pathway Effectors Associate with Worse Prognosis in BRAFV600E -Driven Papillary Thyroid Cancer Patients

PURPOSE

The extent to which routine genomic sequencing can identify relevant secondary genomic alterations among BRAF^V600E -mutant papillary thyroid carcinoma (PTC) is unknown. Such markers would prove highly valuable for prognostic purposes.

EXPERIMENTAL DESIGN

We reviewed clinicopathologic data of 225 patients with BRAF^V600E -mutant PTC and integrated them with genomic data derived from targeted next-generation sequencing (NGS) on tumor specimens. We defined patient subgroups based on bona fide secondary oncogenic events (separate from BRAF^V600E ) and compared their clinical features and outcomes with those without additional oncogenic alterations.

RESULTS

Additional oncogenic alterations were identified in 16% of tumors. Patients in the "BRAF+additional mutations" group were more likely to be at high American Thyroid Association (ATA) risk of recurrence (48.6% vs. 17.6%; P = 0.0009), had larger baseline tumor (2.7 vs. 1.9 cm; P = 0.0005) and more advanced stage at presentation (14.3% vs. 1.1% stage 4; P < 0.0001). Importantly, over a 65-month follow-up, disease-specific mortality (DSM) was increased when additional mutations were identified (13.8% vs. 1.4% in the BRAF-only group; P = 0.005). Separately, we identified a subcluster of patients harboring oncogenic mutations in key effectors of the PI3K/AKT/mTOR pathway, which were independently associated with DSM (OR = 47.9; 95% confidence interval, 3.5-1,246.5; P = 0.0043).

CONCLUSIONS

Identification of additional PIK3/AKT/mTOR alterations in patients with BRAF^V600E -mutant PTC provides important and actionable prognostic risk stratification. These data support genomic profiling of PTC tumors to inform prognosis and clinical strategy.

Papillary Thyroid Carcinoma with High-Grade Features Versus Poorly Differentiated Thyroid Carcinoma: An Analysis of Clinicopathologic and Molecular Features and Outcome

Background: Similar to poorly differentiated thyroid carcinoma (PDTC), papillary thyroid carcinoma with high-grade features (PTC HGF) demonstrates increased mitotic activity and/or necrosis; however, PTC HGF is excluded from the World Health Organization (WHO) definition of PDTC based on maintained nuclear features of PTC. Methods: Consecutive tumors that met criteria for PTC HGF, defined as tumors with maintained nuclear features of PTC and mitoses numbering 5 or more per 10 contiguous high-power fields and/or tumor necrosis, and PDTC (defined as per the WHO criteria) were identified. Clinicopathologic characteristics, follow-up data, and targeted next-generation sequencing results were compared between groups. Results: There were 15 PTC HGF and 47 PDTC. PTC HGF was associated with a higher rate of pT4 disease (53% vs. 13%, p = 0.0027) and lymph node metastases (73% vs. 38%, p = 0.049). The disease-specific survival was worse for patients with PTC HGF compared with those with PDTC using Kaplan-Meier estimation (p < 0.001) and was worse in subgroup analysis evaluating patients with widely invasive PDTC (i.e., those with a similar rate of pT4 disease) and PTC HGF (p = 0.040). PTC HGF had a higher BRAF^V600E mutation rate (42% vs. 3%; p = 0.003), a trend toward more gene fusions (25% vs. 3%; p = 0.052), and a higher rate of relative gain of 1q (67% vs. 15%; p = 0.002) than PDTC. Conclusions: Our results demonstrate that PTC HGF are important to recognize based on their aggressive behavior. The molecular differences between PTC HGF and PDTC suggest that PTC HGF should be considered a distinct group from PDTC.

Genomic profile of columnar cell variant of papillary thyroid carcinoma

BACKGROUND AND AIMS

Columnar cell variant (CCV) is a rare papillary thyroid carcinoma subtype. The majority of CCV occur in older patients and are large, invasive tumours that pursue an aggressive clinical course. Rare well-circumscribed CCV occur in younger female patients and are comparatively indolent.

METHODS AND RESULTS

We retrospectively identified CCV with material available to perform targeted next-generation sequencing and correlated molecular results with clinicopathological features and outcome. Our cohort was comprised of nine CCV. Nearly all were aggressive tumours; however, one was predominantly well-circumscribed and arose in a thyroglossal duct cyst of a 26-year-old woman who had no evidence of disease at last follow-up. Seven (78%) cases demonstrated activating oncogenic driver alterations in BRAF, including BRAF V600E, an activating N486_P490del deletion, and BRAF-AGK fusions. Activating RAS mutations were seen in two (22%) cases. Additionally, three (33%) cases had TERT promoter mutations, four (44%) had loss of the tumour suppressor CDKN2A and one (11%) case had a loss of function TP53 mutation. Most cases (89%) also demonstrated copy number alterations, including recurrent gain of chromosome 1q (five cases) and losses of chromosome 9p (three cases) and 22q (four cases). The one case without secondary pathogenic mutations or copy number alterations was the tumour in the 26-year-old woman.

CONCLUSIONS

We found that CCV is primarily a BRAF-driven tumour, with most also harbouring secondary oncogenic mutations and multiple chromosomal gains and losses. Moreover, our findings suggest that molecular analysis could potentially be used to help risk stratify CCV.

Role of Sonographic Characteristics of Thyroid Bed Lesions Identified Following Thyroidectomy in the Diagnosis or Exclusion of Recurrent Cancer

Background US of the thyroid bed in patients with thyroid cancer often depicts small lesions, but it is unclear whether US characteristics of lesions can help predict cancer recurrence. Purpose To determine whether size or US features of lesions in the thyroid bed after thyroidectomy in conjunction with clinical features can help predict thyroid cancer recurrence. Materials and Methods With use of a US reporting database, all patients imaged between July 2006 and June 2016 with an indication of post-thyroidectomy follow-up were retrospectively identified. Recorded data included patient demographic characteristics; date of thyroidectomy; thyroid cancer type; presence, size, and US characteristics of thyroid bed lesions; and results of fine-needle aspiration (FNA). Images were reviewed for lesions that underwent FNA. The Fisher exact test was used for analysis. Results A total of 1885 patients (mean age ± standard deviation, 48 years ± 15; 1493 female patients) underwent 5732 US examinations. Most patients (1541 of 1885 [82%]) had papillary cancer. Overall, 3163 thyroid bed lesions were reported in 5732 US examinations (40.4%). More than half of these lesions (1860 of 3163 [58.8%]) had a maximum measurement of 6 mm or greater. FNA was performed in 144 of the 3163 lesions (4.6%), of which 61 (42.4%) were malignant, 33 (22.9%) were benign, and 50 (34.7%) were nondiagnostic. Five nondiagnostic lesions eventually proved malignant. Only the presence of punctate echogenicities in the lesion (28 of 61 malignant lesions [45.9%]; three of 33 benign lesions [9%]; 12 of 50 nondiagnostic lesions [24%]; P < .001) or the history of positive lymph nodes at thyroidectomy (44 of 61 malignant lesions [72.1%]; 10 of 33 benign lesions [30%]; 19 of 50 nondiagnostic lesions [38%]; P < .001) were associated with malignancy. Of 3019 thyroid bed lesions that did not undergo FNA, three were malignant and 2248 showed no growth at follow-up US ranging from 6 months to 10 years and are presumed benign. Of the 1303 lesions smaller than 6 mm, only two (0.2%) were malignant. Conclusion Small lesions are commonly found in the thyroid bed after thyroidectomy, and most are likely to be benign. Lesions smaller than 6 mm with no punctate echogenicities had a minimal risk for malignancy. © RSNA, 2021 See also the editorial by Grant and Malhi in this issue.

Genomics and Epigenomics of Medullary Thyroid Carcinoma: From Sporadic Disease to Familial Manifestations

Our understanding of the genomics and epigenomics of medullary thyroid carcinoma (MTC) has advanced since the initial recognition of RET as a driver of MTC tumorigenesis in familial MTC. We now have insight into the frequency and prognostic significance of specific RET mutations in sporadic MTC. For example, the most common RET mutation in sporadic MTC is the RET Met918Thr mutation, the same mutation that underlies MEN2B and a poor prognosticator. This mutation is relatively infrequent in medullary thyroid microcarcinomas but is over-represented in advanced-stage disease. RAS mutations are detected in 70% of sporadic, RET wild-type MTC. Although next-generation and whole-exome sequencing studies have shown that tumors that are wild-type for RET and RAS mutations essentially lack other recurrent mutations, additional pathways and epigenetic alterations have been implicated in MTC tumorigenesis. Increased insight into the clinical course of patients with familial MTC with specific RET mutations has guided treatment recommendations for these patients. Finally, an understanding of the genomics has informed treatment for patients with advanced MTC. In this review, we will examine the genomics and epigenomics of sporadic and familial MTC, along with the prognostic significance of molecular alterations, management of patients with germline RET mutations, and treatment strategies for MTC patients.

Intestinal metaplasia of the urinary tract harbors potentially oncogenic genetic variants

In the urinary tract, there is an uncertain relationship between intestinal metaplasia (IM), primary adenocarcinoma, and urothelial carcinoma. Although IM is usually found adjacent to concurrent urothelial carcinoma or adenocarcinoma, small retrospective series have shown that most bladder biopsies with only IM do not subsequently develop cancer. However, IM with dysplasia does seem to be associated with a higher risk of concurrent malignancy or progressing to cancer. Since the molecular landscape of these lesions has remained largely unexplored, there are significant uncertainties about the oncogenic potential of IM in the bladder and urethra. This study investigated the presence of potentially oncogenic genetic variants in cases of IM with and without dysplasia. Twenty-three (23) cases of IM (3 urethra, 20 bladder) were sequenced using a solid tumor next-generation sequencing panel. Of these, five contained IM with high-grade dysplasia (including a case with paired IM-adenocarcinoma and another with paired IM-urothelial carcinoma) and 18 lacked dysplasia. Oncogenic genetic variants were found in all cases of IM with high-grade dysplasia and in five non-dysplastic IM cases, including mutations and copy number variants commonly seen in primary adenocarcinoma of the bladder and urothelial carcinoma. This study demonstrates that IM can harbor potentially oncogenic genetic variants, suggesting that it might represent a cancer precursor or a marker of increased cancer risk in a subset of cases.

Unexpected Pathogenic RET p.V804M Variant Leads to the Clinical Diagnosis and Management of Medullary Thyroid Carcinoma

Patient: Female, 62-year-old

Final Diagnosis: Medullary thyroid microcarcinoma

Symptoms: No pain or swelling in her neck • no dysphagia or odynophagia • no changes in voice

Medication: —

Clinical Procedure: Genetic analysis

Specialty: Genetics

Hürthle cell lesions of the thyroid: Progress made and challenges remaining

Hürthle cell-predominant thyroid fine needle aspirations (FNA) are encountered frequently in routine practice, yet they are often challenging to diagnose accurately and are associated with significant interobserver variability. This is largely due to the ubiquity of Hürthle cells in thyroid pathology, ranging from nonneoplastic conditions to aggressive malignancies. Although limitations in cytomorphologic diagnoses likely will remain for the foreseeable future, our knowledge of the molecular pathogenesis of Hürthle cell neoplasia and application of molecular testing to cytologic material have increased dramatically within the past decade. This review provides context behind the challenges in diagnosis of Hürthle cell lesions and summarizes the more recent advances in diagnostic tools.

Data set for reporting carcinoma of the thyroid: recommendations from the International Collaboration on Cancer Reporting

Thyroid cancer therapy is increasingly tailored to patients' risk of recurrence and death, placing renewed importance on pathologic parameters. The International Collaboration on Cancer Reporting (ICCR), an organization promoting evidence-based, internationally agreed-upon standardized pathology data sets, is the ideal conduit for the development of a pathology reporting protocol aimed at improving the care of patients with thyroid carcinomas. An international expert panel reviewed each element of thyroid pathology reporting. Recommendations were made based on the most recent literature and expert opinion.The data set uses the most recent World Health Organization (WHO) classification for the purpose of a more clinically and prognostically relevant nomenclature. One example is the restriction of the term minimally invasive follicular carcinoma to tumors with capsular invasion only. It reinforces the already established criteria for blood vessel invasion adopted by the most recent WHO classification and Armed Forces Institute of Pathology fascicle. It emphasizes the importance of the extent of blood vessel invasion and extrathyroid extension to better stratify patients for appropriate therapy. It is the first data set that requires pathologists to use the more recently recognized prognostically powerful parameters of mitotic activity and tumor necrosis. It highlights the importance of assessing nodal disease volume in predicting the risk of recurrence.The ICCR thyroid data set provides the tools to generate a report that will guide patient treatment in a more rational manner aiming to prevent the undertreatment of threatening malignancies and spare patients with indolent tumors the morbidity of unnecessary therapy. We recommend its routine use internationally for reporting thyroid carcinoma histology.

Histopathologic Features and Clinical Outcome of Anaplastic Thyroid Carcinoma with a Minor Anaplastic Component

Although prior studies have reported that patients with anaplastic thyroid carcinoma (ATC) with a focal anaplastic component may have a prolonged survival compared to other ATC patients, the outcome data are limited. We evaluated a cohort of ATC resected between 2003 and 2018. Tumor slides were reviewed to confirm the diagnosis and to identify cases with a minor ATC component (defined as comprising < 10% of the tumor). We evaluated the clinical outcome of these patients compared to that of all other cohort patients (characterized as having conventional ATC). Our cohort was composed of 24 cases of ATC that underwent resection, including 8 (33%) with a minor ATC component. Tumors with a minor ATC component were predominantly associated with papillary thyroid carcinoma. For patients with tumors with a minor ATC component, the 1-year and 2-year survival rates and median survival for patients who died of disease were 88%, 43%, and 17 months (range 6-73 months), respectively. In comparison, for patients with conventional ATC, the 1-year and 2-year survival rates and median survival for patients who died of disease were 56%, 44%, and 7 months (range 2-26 months), respectively. There was no difference in 1- and 2-year survival or overall survival by Kaplan-Meier analysis for patients with tumors with a minor ATC component and those with conventional ATC. In conclusion, the difference in overall survival between ATC groups in our cohort was not significant; however, this could be due to the small cohort size or due to characteristics of our group with a minor ATC component; that is, no tumors in this group were limited to the thyroid (stage IVA), resectability with negative margins was infrequent, and 38% of this group had distant metastases at diagnosis (stage IVC).

Genomic Predictors of Good Outcome, Recurrence, or Progression in High-Grade T1 Non-Muscle-Invasive Bladder Cancer

High-grade T1 (HGT1) bladder cancer is the highest risk subtype of non-muscle-invasive bladder cancer with unpredictable outcome and poorly understood risk factors. Here, we examined the association of somatic mutation profiles with nonrecurrent disease (GO, good outcome), recurrence (R), or progression (PD) in a cohort of HGT1 patients. Exome sequencing was performed on 62 HGT1 and 15 matched normal tissue samples. Both tumor only (TO) and paired analyses were performed, focusing on 95 genes known to be mutated in bladder cancer. Somatic mutations, copy-number alterations, mutation load, and mutation signatures were studied. Thirty-three GO, 10 R, 18 PD, and 1 unknown outcome patients were analyzed. Tumor mutational burden (TMB) was similar to muscle-invasive disease and was highest in GO, intermediate in PD, and lowest in R patients (P = 0.017). DNA damage response gene mutations were associated with higher TMB (P < 0.0001) and GO (P = 0.003). ERCC2 and BRCA2 mutations were associated with GO. TP53, ATM, ARID1A, AHR, and SMARCB1 mutations were more frequent in PD. Focal copy-number gain in CCNE1 and CDKN2A deletion was enriched in PD or R (P = 0.047; P = 0.06). APOBEC (46%) and COSMIC5 (34%) signatures were most frequent. APOBEC-A and ERCC2 mutant tumors (COSMIC5) were associated with GO (P = 0.047; P = 0.0002). pT1b microstaging was associated with a genomic cluster (P = 0.05) with focal amplifications of E2F3/SOX4, PVRL4, CCNE1, and TP53 mutations. Findings were validated using external public datasets. These findings require confirmation but suggest that management of HGT1 bladder cancer may be improved via molecular characterization to predict outcome. SIGNIFICANCE: Detailed genetic analyses of HGT1 bladder tumors identify features that correlate with outcome, e.g., high mutational burden, ERCC2 mutations, and high APOBEC-A/ERCC2 mutation signatures were associated with good outcome.

Histological features of BRAF V600E-mutant anaplastic thyroid carcinoma

AIMS

Treatment with a BRAF inhibitor, alone or in combination with a MEK inhibitor, may be considered for BRAF-mutant anaplastic thyroid carcinoma (ATC). The purpose of this study was to characterise the histology of BRAF V600E-mutant ATC.

METHODS AND RESULTS

We identified 28 ATC that were consecutively resected between 2003 and 2019. All tumour slides for each case were evaluated for the presence of a precursor tumour and for ATC morphology (sarcomatoid, pleomorphic giant cell, epithelioid or squamous). BRAF V600E mutation status was determined by BRAF V600E IHC or molecular analysis (OncoPanel NGS). Eighteen (64%) ATC had an associated well-differentiated precursor, including 10 (36%) with associated papillary thyroid carcinoma (PTC) and eight (29%) with associated follicular thyroid carcinoma (FTC) or Hürthle cell carcinoma (HCC). Most ATC (19 cases, 68%) demonstrated a mixed anaplastic morphology. Squamous morphology was present in four cases. Ten (36%) ATC had a BRAF V600E mutation. All ATC that had a PTC precursor had a BRAF V600E mutation (and all ATC with a BRAF V600E mutation had a PTC precursor), whereas no ATC with an FTC or HCC precursor had a BRAF V600E mutation. All four cases of ATC with a squamous morphology had a PTC precursor and a BRAF V600E mutation.

CONCLUSION

In our cohort, the presence of a PTC precursor predicted the presence of the BRAF V600E mutation, whereas ATC with an FTC or HCC precursor lacked a BRAF V600E mutation. A squamous morphology was associated with the presence of a PTC precursor and a BRAF V600E mutation.

Anaplastic thyroid carcinoma

Anaplastic thyroid carcinoma (ATC) is a rare but significant malignancy due to its high mortality rate. Rendering an accurate diagnosis is crucial given the prognostic implications and treatment ramifications. Based on the prognostic significance of the extent of invasion of the primary tumor, T staging for ATC changed in the most recent edition of the American Joint Committee on Cancer (AJCC) staging manual. In the past 5 years there has been a rapid increase in our understanding of the molecular basis of ATC which has provided the basis for targeted therapy for some ATC patients. In this review, ATC prognostic factors, histologic and immunotypic features, staging updates, and molecular alterations, with an emphasis on those that may impact treatment, will be discussed.

Completion Thyroidectomy is Less Common Following Updated 2015 American Thyroid Association Guidelines

BACKGROUND

The 2015 American Thyroid Association (ATA) guidelines recommended that low-risk, differentiated thyroid cancers (DTC) between 1 and 4 cm may be treated with thyroid lobectomy alone. We sought to determine the effect of these guideline changes on the rate of completion thyroidectomy (CT) for low-risk DTC and factors influencing surgical decision-making.

METHODS

All patients from 2014 to 2018 who received an initial thyroid lobectomy at our institution with final pathology demonstrating DTC were included. Patients were divided into "pre" and "post" guideline cohorts (2014-2015 and 2016-2018, respectively). The rate of CT was compared between the two cohorts. Patient demographics and tumor characteristics were examined for association with CT.

RESULTS

A total of 163 patients met study criteria: 63 patients in the 2014-2015 ("pre") and 100 in the 2016-2018 ("post") group. In the "pre" period, 41 (65.1%) patients received CT compared with 43 (43.0%) in the "post" period (p < 0.01)-a 34% decrease in the rate of completion surgery (p < 0.01). Of low-risk patients with DTC between 1 and 4 cm in size, 17 of 35 (48.6%) received CT in the "pre" period compared with 15 of 60 (25.0%) in the post period-a 48.6% decrease in the rate of completion surgery (p = 0.02). Greater tumor size, capsular invasion, and multifocality were associated with CT in low-risk "post" guideline patients (p < 0.05 for all).

CONCLUSIONS

The rate of CT decreased significantly by 48.6% for low-risk patients with DTC between 1 and 4 cm, demonstrating recognition of the 2015 ATA guidelines. However, 25% of these patients underwent CT, suggesting additional factors influencing the decision for further treatment.

A phase II study of nivolumab (N) plus ipilimumab (I) in radioidine refractory differentiated thyroid cancer (RAIR DTC) with exploratory cohorts in anaplastic (ATC) and medullary thyroid cancer (MTC)

6513

Background: Treatment options for aggressive TC are limited. Pre-clinical data suggests efficacy of CTLA-4 plus PD-1 blockade in aggressive RAIR TC. Methods: This investigator initiated phase II study tested N (3mg/kg every 2 weeks) plus I (1mg/kg every 6 weeks) until disease progression or completion of 24 mo of treatment in RAIR differentiated TC including poorly differentiated TC (PDTC) with exploratory cohorts in anaplastic (ATC) and medullary TC (MTC). Radiographic response rate by RECIST v1.1 (CR+PR) was primary endpoint. At least 6 pts with disease response among n=32 DTC provided 84% power to distinguish between a 10% and a 25% RR (one-sided 9% binomial test). Results: Accrual is complete with n=32 patients with DTC, 10 with ATC and 7 with MTC enrolled between October 2017 and May 2019. Thirty-two DTC included: n=17 papillary, n=7 Hurthle, n=4 follicular TC, n=4 PDTC. Among n=49, median (range) age was 65 (30-88), 51% (25/49) were female. To date, in DTC, 3/32 achieved a PR (n=2 Hurthle and n=1 PDTC), 9.4% RR (.95CI:2%-25%). One near complete response has been observed. Among pts w ATC, 3/ 10 profound PR by RECIST occurred (30% RR, .95CI: 7%-65%). Among them, two remain without clear evidence of disease at 26 and 13 mo after treatment start. No PR's were observed in MTC. Most frequent grade 3-4 TRAEs were as expected and included increased lipase (n=8), increased serum amylase (n=4). There was an unexpected number of treatment related adrenal insufficiency (AI) (n=4) which was associated with long PFS (range 10.1—16.4+mo). Conclusions: N+I appears to have considerable activity in ATC. In unselected RAIR DTC, activity was low but responses were seen in PDTC and Hurthle cell TC. Exceptional responses with prolonged remissions were observed. Clinical trial information: NCT03246958 .

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.

Thyroid Tumors You Don't Want to Miss

This article examines more uncommon thyroid entities, including anaplastic thyroid carcinoma, poorly differentiated thyroid carcinoma, rare papillary thyroid carcinoma variants, medullary thyroid carcinoma, non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), and multiple adenomatous nodules in the setting of Cowden syndrome. These entities were chosen based on their clinical significance and because they can be diagnostically challenging due to their morphologic diversity and overlap with other thyroid tumors. This article addresses the diagnostic features of each entity, focusing on how to avoid potential pitfalls and mimics while also highlighting the clinical implications of each diagnosis.

Genetic Characteristics of Aldosterone-Producing Adenomas in Blacks

Somatic mutations have been identified in aldosterone-producing adenomas (APAs) in genes that include KCNJ5, ATP1A1, ATP2B3, and CACNA1D. Based on independent studies, there appears to be racial differences in the prevalence of somatic KCNJ5 mutations, particularly between East Asians and Europeans. Despite the high cardiovascular disease mortality of blacks, there have been no studies focusing on somatic mutations in APAs in this population. In the present study, we investigated genetic characteristics of APAs in blacks using a CYP11B2 (aldosterone synthase) immunohistochemistry-guided next-generation sequencing approach. The adrenal glands with adrenocortical adenomas from 79 black patients with primary aldosteronism were studied. Seventy-three tumors from 69 adrenal glands were confirmed to be APAs by CYP11B2 immunohistochemistry. Sixty-five of 73 APAs (89%) had somatic mutations in aldosterone-driver genes. Somatic CACNA1D mutations were the most prevalent genetic alteration (42%), followed by KCNJ5 (34%), ATP1A1 (8%), and ATP2B3 mutations (4%). CACNA1D mutations were more often observed in APAs from males than those from females (55% versus 29%, P=0.033), whereas KCNJ5 mutations were more prevalent in APAs from females compared with those from males (57% versus 13%, P<0.001). No somatic mutations in aldosterone-driver genes were identified in tumors without CYP11B2 expression. In conclusion, 89% of APAs in blacks harbor aldosterone-driving mutations, and unlike Europeans and East Asians, the most frequently mutated aldosterone-driver gene was CACNA1D. Determination of racial differences in the prevalence of aldosterone-driver gene mutations may facilitate the development of personalized medicines for patients with primary aldosteronism.

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.

Ketogenic diet combined with antioxidant N-acetylcysteine inhibits tumor growth in a mouse model of anaplastic thyroid cancer

BACKGROUND

Anaplastic thyroid cancer is an aggressive and fatal malignancy. Many advanced cancers are characterized by glucose dependency, leading to oxidative stress and cellular proliferation. Therefore, we sought to determine if a low glucose environment (in vitro) or a ketogenic diet (in vivo) could inhibit anaplastic thyroid cancer tumor growth when combined with the antioxidant N-acetylcysteine.

METHODS

In vivo, nude mice were injected with the anaplastic thyroid cancer cell line 8505C (n = 6/group). Group 1 was fed a standard diet; Group 2 was fed a ketogenic diet; Group 3 was given standard diet with N-acetylcysteine (40 mM in the drinking water); and Group 4 was fed ketogenic diet with N-acetylcysteine. Tumor volumes, ketones, and glucose were measured. H&E stains and immunohistochemistry for Ki-67 and Caspase 3 were performed on the tumors. In vitro, 8505C cells were cultured in high glucose (25 mM), low glucose (3 mM), high glucose plus N-acetylcysteine (200 uM), or low glucose plus N-acetylcysteine for 96 hours. We performed CyQUANT proliferation (Thermo Fisher Scientific, Waltham, MA), Seahorse glycolytic stress (Agilent, Santa Clara, CA), and reactive oxidative stress assays.

RESULTS

Ketogenic diet plus N-acetylcysteine decreased in vivo tumor volume compared to standard diet (22.5 ± 12.4 mm³ vs 147 ± 54.4 mm³, P < .05) and standard diet plus N-acetylcysteine (P < .05). Blood ketone levels were significantly higher for the mice in the ketogenic diet group compared to standard diet (1.74 mmol/L vs 0.38 mmol/L at week 5, P < .001). However, blood glucose levels were not significantly different between ketogenic diet and standard diet groups. Cells cultured in low glucose plus N-acetylcysteine had significantly reduced proliferation compared to high glucose (98.1 ± 5.0 relative fluorescence units vs 157.8 ± 2.1 relative fluorescence units, P < .001). Addition of N-acetylcysteine to low glucose lowered glycolysis function compared to high glucose (39.0 ± 2.2 mpH/min/cell vs 89.1 ± 13.2 mpH/min/cell, P < .001) and high glucose plus N-acetylcysteine (37.4 ± 2.5 mpH/min/cell vs 70.3 ± 3.3 mpH/min/cell, P < .001). Low glucose plus N-acetylcysteine decreased reactive oxidative stress compared to high glucose (119 ± 34.7 relative fluorescence units vs 277 ± 16.0 relative fluorescence units, P = .014).

CONCLUSION

The combination of a ketogenic diet or glucose restriction with the antioxidant- N-acetylcysteine significantly reduced tumor growth in vivo and in vitro. Further studies are warranted to explore these metabolic therapies in anaplastic thyroid cancer.

Prognostic Significance of Extent of Invasion in Poorly Differentiated Thyroid Carcinoma

Background: The 2017 World Health Organization (WHO) Classification of Tumors of Endocrine Organs defines poorly differentiated thyroid carcinoma (PDTC) as a tumor with conventional criteria of malignancy (capsular penetration or vascular invasion) with solid, insular, or trabecular growth, a lack of nuclear features of papillary thyroid carcinoma, and increased mitotic activity, tumor necrosis, or convoluted nuclei. The extent of invasion has been shown to be prognostic in follicular thyroid carcinoma and Hürthle cell carcinoma. Our aim was to evaluate how extent of invasion impacts clinical outcome for PDTC. Methods: We retrospectively identified 47 consecutively diagnosed cases of PDTC that were resected between 2005 and 2018. All cases were reviewed to confirm that the tumors met the 2017 Endocrine WHO criteria of PDTC. In addition, tumors were categorized as follows: encapsulated with capsular penetration only, encapsulated with focal vascular invasion (fewer than four foci), encapsulated with extensive vascular invasion (four or more foci), or widely invasive. Histopathologic characteristics and clinical outcome data were recorded. Results: A total of 47 cases of PDTC, including 15 oncocytic tumors, were identified from 28 (60%) women and 19 (40%) men (mean age of 57 years at diagnosis). The mean tumor size was 4.3 cm. Mitoses numbered 8 per 10 high-power fields (HPF) on average (range: 1-34), and necrosis was present in 21 (45%) cases. Eight (17%) cases were encapsulated with capsular penetration only, 5 (11%) were encapsulated with focal vascular invasion, 18 (38%) were encapsulated with extensive vascular invasion, and 16 (34%) were widely invasive. Of the 42 (89%) patients with follow-up data, 7 (17%) died of disease (with a mean survival time of 6.4 years), 11 (26%) have distant metastatic disease, and 24 (57%) have no evidence of disease (mean follow-up 5.6 years). Eight (19%) patients presented with M1 disease at diagnosis. The 5-year disease-free survival (DFS) for patients with M0 disease at diagnosis was 100% for patients with tumors with capsular invasion only or focal vascular invasion (n = 7), 73% for patients with encapsulated tumors with extensive vascular invasion (n = 11), and 17% for patients with widely invasive PDTCs (n = 6). DFS estimates by Kaplan-Meier analysis were significantly different between these groups (p = 0.0016). Conclusions: Extent of invasion appears to be an important parameter that affects clinical outcome for patients with PDTC. In our cohort, patients with encapsulated PDTC with capsular invasion only or focal vascular invasion had an excellent outcome.

Characterization of Activating Mutations of the MEK1 Gene in Papillary Thyroid Carcinomas

Background: Genetic alterations activating the mitogen-activated protein kinase (MAPK) signaling pathway, most commonly BRAF and RAS mutations, are common in papillary thyroid carcinoma (PTC). Somatic mutations of the MEK gene, also known as mitogen-activated protein kinase kinase 1 (MAP2K1), coding for a signaling protein downstream of BRAF, have been found in several cancer types. The goal of this study was to investigate if functional MEK1 mutations occur in thyroid cancer (TC). Methods: We analyzed MEK1 mutation status in a series of 101 PTCs lacking other known driver mutations using Sanger sequencing and targeted next-generation sequencing. In addition, 64 follicular and Hürthle cell carcinomas and 32 follicular adenomas were studied. The occurrence of MEK1 mutations was evaluated using another series of thyroid tumors studied by targeted next-generation sequencing. Western blot and RNA-seq analyses were performed on selected tumors. Results: We detected MEK1 mutations in 2/101 (2%) PTCs that otherwise had no known genetic alterations, in 0/64 follicular and Hürthle cell carcinomas, and in 0/32 follicular adenomas. Two positive tumors carried the same in-frame deletion p.L98_I103del; K104I (c.292_309del18; c.311A>T) located in exon 3 of the gene. One additional MEK1 mutation was identified following routine molecular tumor profiling. The tumor had an in-frame deletion p.I99_K104del (c.294_311del18) also located in exon 3. Western blot analysis of one of the tumors showed activation of the MAPK pathway. Using RNA-seq analysis to evaluate changes in gene expression, these tumors were RAS-like and showed a high thyroid differentiation score. Phenotypically, the MEK1-positive PTCs were all encapsulated and had a predominantly or exclusively follicular architecture, being diagnosed as a classic papillary type with a significant follicular pattern ( × 2) or follicular variant PTC ( × 1). Follow-up was available for 2 patients, with no evidence of disease found 2 and 10 years postsurgery. Conclusions: In this study, we report the occurrence of functional MEK1 mutations in PTC. All mutations are in-frame deletions in exon 3 of MEK1, representing another mechanism of activation of the MAPK pathway in papillary carcinomas with a predominantly follicular growth pattern.