Thyroid nodules with DICER1 mutation or PTEN alteration: A comparative cytologic, clinical, and molecular study of 117 FNA cases.

BACKGROUND: DICER1 mutations and PTEN alterations are increasingly detected by thyroid fine-needle aspiration (FNA). Both are associated with nodular thyroid disease and cancer. The authors analyzed a large comparative thyroid FNA cohort with DICER1 mutation or PTEN alteration. METHODS: A total of 117 thyroid FNAs with DICER1 or PTEN alterations were retrieved from the databases of two academic medical institutions. Demographic, clinical, and radiologic data were collected; FNA slides were analyzed for 29 cytomorphologic features. RESULTS: Of 117 thyroid FNAs, 36 (30.8%) had DICER1 mutation and 81 (69.2%) showed PTEN alteration. The DICER1 cohort had 33 (91.7%) females and three (8.3%) males (mean, 40.9 years); 61.8% had multinodular disease. FNAs were classified as atypia of undetermined significance (AUS), 23 (63.9%); follicular neoplasm (FN), 12 (33.3%); and malignant, 1 (2.8%). The PTEN subgroup had 66 (81.5%) females and 15 (18.5%) males (mean, 55.2 years) with increased multinodular disease (93.8%, p = .0016). PTEN FNAs had greater cytologic diversity: non-diagnostic, 2 (2.5%); benign, 5 (6.2%); AUS, 44 (54.3%); FN, 24 (29.6%); and malignant, 6 (7.4%). Both DICER1 and PTEN cases showed a range of resected tumor subtypes. The DICER1 cohort included thyroblastoma, and the PTEN group included anaplastic carcinoma. The cytomorphology of DICER1 and PTEN cases showed overlapping features, especially microfollicular patterns. Minor cytomorphologic differences included papillary patterns in DICER1 (p = .039), and oncocytic changes (p < .0001) in PTEN. CONCLUSIONS: DICER1 and PTEN FNAs reveal many cytologic similarities. DICER1 patients are younger, and PTEN patients had multinodular disease. Awareness of these genetic cohorts can identify patients at risk for thyroid cancer.

Risks of malignancy in the major nongynecologic cytopathology reporting systems: Critiques and discussions.

The ever-increasing popularity of standardized systems for reporting cytopathology has led in part to much attention to and importance of the risk stratification schemes, especially the risks of malignancy (ROMs), which are associated with the different diagnostic categories and upon which recommendations for clinical management are based. However, it is well known that the ROM calculations are based on retrospective reviews of the existing literature, representing a heterogeneous patient population, and are plagued by significant biases and variations. Statistically, the ROM represents the post-test probability of malignancy, which changes with the test result and with the prevalence of malignancy (or pretest probability) in an individual practice setting and individual patient presentation. Therefore, the clinical utility of the ROM is questioned and likely needs a second look in the nongynecologic cytopathology reporting systems. In this communication, the authors discuss the status of the ROM estimates according to the most commonly used nongynecologic reporting systems, including for thyroid, salivary glands, and others, highlighting similarities and differences with a focus on the limitations of ROM estimates and their application in clinical practice.

Second edition of the Milan System for Reporting Salivary Gland Cytopathology: Refining the role of salivary gland FNA.

The use of standardized reporting systems for nongynecologic cytopathology has made enormous gains in popularity during the past decade, including for thyroid fine-needle aspiration, urine cytology, serous effusions, pancreas, lymph nodes, lung, and more. In February 2018, the first edition Atlas of the Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) was published. The MSRSGC defines six diagnostic fine-needle aspiration categories encompassing the spectrum of Non-Neoplastic, benign, and malignant lesions of the salivary glands. The goal of the MSRSGC is to combine each diagnostic category with a defined risk of malignancy and a specific clinical and/or surgical management algorithm. Since its initial publication in 2018, more than 200 studies and commentaries have been published confirming the role of the MSRSGC. The second edition of the MSRSGC, published in July 2023, includes refined risks of malignancy based on systematic reviews and meta-analyses, a new chapter summarizing the use of salivary gland imaging, new advances in ancillary testing, and updates in nomenclature. CONCISE SENTENCE: The second edition of the Milan System for Reporting Salivary Gland Cytopathology, published in July 2023, includes refined risks of malignancy based on systematic reviews and meta-analyses, a new chapter summarizing the use of salivary gland imaging, new advances in ancillary testing, updates in nomenclature, and a guide to the practical application of the latest ancillary markers for the diagnosis of selected salivary gland fine-needle aspiration cases.

Second edition of the Milan System for Reporting Salivary Gland Cytopathology: Refining the role of salivary gland FNA.

The use of standardized reporting systems for non-gynecologic cytopathology has made enormous gains in popularity during the past decade, including for thyroid fine-needle aspiration, urine cytology, serous effusions, pancreas, lymph nodes, lung, and more. In February 2018, the first edition Atlas of the Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) was published. The MSRSGC defines six diagnostic fine-needle aspiration categories encompassing the spectrum of non-neoplastic, benign, and malignant lesions of the salivary glands. The goal of the MSRSGC is to combine each diagnostic category with a defined risk of malignancy and a specific clinical and/or surgical management algorithm. Since its initial publication in 2018, more than 200 studies and commentaries have been published confirming the role of the MSRSGC. The second edition of the MSRSGC, published in July 2023, includes refined risks of malignancy based on systematic reviews and meta-analyses, a new chapter summarizing the use of salivary gland imaging, new advances in ancillary testing, and updates in nomenclature.

Second edition of the Milan System for Reporting Salivary Gland Cytopathology: Refining the role of salivary gland FNA.

The use of standardised reporting systems for non-gynaecologic cytopathology has made enormous gains in popularity during the past decade, including for thyroid fine-needle aspiration, urine cytology, serous effusions, pancreas, lymph nodes, lung and more. In February 2018, the first edition of the Atlas of the Milan System for Reporting Salivary Gland Cytopathology (MSRSGC) was published. The MSRSGC defines six diagnostic fine-needle aspiration categories encompassing the spectrum of non-neoplastic, benign and malignant lesions of the salivary glands. The goal of the MSRSGC is to combine each diagnostic category with a defined risk of malignancy and a specific clinical and/or surgical management algorithm. Since its initial publication in 2018, more than 200 studies and commentaries have been published, confirming the role of the MSRSGC. The second edition of the MSRSGC, published in July 2023, includes refined risks of malignancy based on systematic reviews and meta-analyses, a new chapter summarising the use of salivary gland imaging, new advances in ancillary testing and updates in nomenclature.

Pitfalls in Thyroid Fine Needle Aspiration Cytopathology: An Approach to Atypical Findings.

BACKGROUND: Thyroid nodules are prevalent among the general population, thus imposing substantial demands upon healthcare providers to establish effective management paradigms when investigating these lesions. A pivotal component in the diagnostic process involves the cytomorphologic evaluation of fine needle aspiration (FNA) specimens extracted from the nodule under scrutiny. This examination serves the critical purpose of enabling a comprehensive assessment for the risk of either a neoplasm or malignancy, thereby providing the clinical team with the requisite information to render decisions regarding potential surgical intervention and/or a structured clinical follow-up. A subset of FNA specimens obtained from the thyroid gland present a vexing challenge for interpretation and cannot be classified based on cytomorphology as either benign or malignant and are classified as "indeterminate" for neoplasm or malignancy. The indeterminate thyroid FNA diagnosis in the third iteration of the Bethesda classification are termed as "atypia of undetermined significance" (AUS). SUMMARY: The thyroid FNA specimens classified as "atypical" constitutes a perplexing category, necessitating considerations such as repeated cytological evaluations, supplementary molecular analyses, diagnostic lobectomy, or vigilant surveillance. This review article draws upon the most recent Bethesda classification guidelines and delineates various potential pitfalls encountered during the interpretation of atypia observed in thyroid fine needle aspiration and histopathologic counterparts. Additionally, it proffers strategic algorithms devised to effectively navigate these diagnostic challenges.

The 2023 Bethesda System for reporting thyroid cytopathology.

Since the publication of the first edition in 2010, The Bethesda System for Reporting Thyroid Cytopathology has allowed cytopathologists to use a standardized, category-based reporting system for thyroid fine needle aspirations. The third edition builds on the success of the 2 earlier editions and offers several key updates. The most important is the assignment of a single name for each of the 6 diagnostic categories: (i) nondiagnostic; (ii) benign; (iii) atypia of undetermined significance; (iv) follicular neoplasm; (v) suspicious for malignancy; and (vi) malignant. Each of the categories has an implied risk of malignancy (ROM), which has been updated and refined based on data reported after the second edition. The third edition offers an average ROM for each category, in addition to the expected range of cancer risk. The atypia of undetermined significance subcategorization is simplified into 2 subgroups based on the implied ROM and molecular profiling. A discussion of pediatric thyroid disease has been added, and pediatric ROMs and management algorithms are discussed in the relevant sections. Nomenclature has been updated to align with the 2022 World Health Organization Classification of Thyroid Neoplasms. Two new chapters have been added: one that addresses the significant and expanded use of molecular and ancillary testing in thyroid cytopathology, and another that summarizes clinical perspectives and imaging findings in thyroid disease.

The 2023 Bethesda System for Reporting Thyroid Cytopathology.

Since the publication of the first edition in 2010, The Bethesda System for Reporting Thyroid Cytopathology has allowed cytopathologists to use a standardized, category-based reporting system for thyroid fine needle aspirations. The third edition builds on the success of the 2 earlier editions and offers several key updates. The most important is the assignment of a single name for each of the 6 diagnostic categories: (i) nondiagnostic; (ii) benign; (iii) atypia of undetermined significance; (iv) follicular neoplasm; (v) suspicious for malignancy; and (vi) malignant. Each of the categories has an implied risk of malignancy (ROM), which has been updated and refined based on data reported after the second edition. The third edition offers an average ROM for each category, in addition to the expected range of cancer risk. The atypia of undetermined significance subcategorization is simplified into 2 subgroups based on the implied ROM and molecular profiling. A discussion of pediatric thyroid disease has been added, and pediatric ROMs and management algorithms are discussed in the relevant sections. Nomenclature has been updated to align with the 2022 World Health Organization Classification of Thyroid Neoplasms. Two new chapters have been added: one that addresses the significant and expanded use of molecular and ancillary testing in thyroid cytopathology, and another that summarizes clinical perspectives and imaging findings in thyroid disease.

Immunohistochemistry in the pathologic diagnosis and management of thyroid neoplasms.

The use of immunohistochemistry cannot be underestimated in the everyday practice of thyroid pathology. It has evolved over the years beyond the traditional confirmation of thyroid origin to molecular profiling and the prediction of clinical behavior. In addition, immunohistochemistry has served to implement changes in the current thyroid tumor classification scheme. It is prudent to perform a panel of immunostains, and the immunoprofile should be interpreted in light of the cytologic and architectural features. Immunohistochemistry can also be easily performed in the limited cellularity specimen preparation generated from thyroid fine-needle aspiration and core biopsy; however, it will require laboratory validation of immunostains specific to these preparations to avoid diagnostic pitfalls. This review discusses the application of immunohistochemistry in thyroid pathology with a focus on limited cellularity preparations.

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.

Unraveling the significance of TSHR mutations in indeterminate thyroid cytology specimens.

OBJECTIVES: We investigated the clinical significance of thyroid-stimulating hormone receptor (TSHR) mutations detected in thyroid fine needle aspiration (FNA) specimens. METHODS: The pathology archives at our institution were reviewed between 2018 and 2021 for indeterminate (Bethesda category III and IV) specimens with Thyroseq® analysis showing TSHR mutations. RESULTS: A total of 2184 cases diagnosed as atypia/follicular lesion of undetermined significance (AUS/FLUS), and 2625 diagnosed as follicular neoplasm/suspicious for follicular neoplasm (FN/SFN) were identified. A total of 1735 AUS/FLUS and 2339 SFN/FN underwent Thyroseq® analysis; 69 showed TSHR mutations (1.6%, 59 female, 10 male, average age: 55 years). Ten cases showed oncocytic features. Twelve patients underwent radionuclide scans within 1 year of FNA:11 were hyperfunctioning. Nodule size and TSH levels were weakly correlated. Twenty-two different TSHR mutations were identified (most common: M453T). A second mutation was found in five cases (EZH1 n = 2, and EIF1AX n = 3). The expression of sodium-iodide transporter (NIS) mRNA was in the range of 0.01%-62.43% out of all sequencing reads, and was elevated in 49 (71%) cases. Surgical pathology follow-up was available in five cases (all benign except one). On follow-up available for 38 cases (mean: 24 months; range: 7-47 months), 34 (89.5%) nodules remained stable and 3 (8%) increased in size. CONCLUSIONS: TSHR mutations in thyroid FNA samples classified as indeterminate are rare, generally benign, and commonly associated with autonomy on scan if performed.

Molecular Profiling of 50 734 Bethesda III-VI Thyroid Nodules by ThyroSeq v3: Implications for Personalized Management.

CONTEXT: Comprehensive genomic analysis of thyroid nodules for multiple classes of molecular alterations detected in a large series of fine needle aspiration (FNA) samples has not been reported. OBJECTIVE: To determine the prevalence of clinically relevant molecular alterations in Bethesda categories III-VI (BCIII-VI) thyroid nodules. METHODS: This retrospective analysis of FNA samples, tested by ThyroSeq v3 using Genomic Classifier and Cancer Risk Classifier at UPMC Molecular and Genomic Pathology laboratory, analyzed the prevalence of diagnostic, prognostic, and targetable genetic alterations in a total of 50 734 BCIII-VI nodules from 48 225 patients. RESULTS: Among 50 734 informative FNA samples, 65.3% were test-negative, 33.9% positive, 0.2% positive for medullary carcinoma, and 0.6% positive for parathyroid. The benign call rate in BCIII-IV nodules was 68%. Among test-positive samples, 73.3% had mutations, 11.3% gene fusions, and 10.8% isolated copy number alterations. Comparing BCIII-IV nodules with BCV-VI nodules revealed a shift from predominantly RAS-like alterations to BRAF V600E-like alterations and fusions involving receptor tyrosine kinases (RTK). Using ThyroSeq Cancer Risk Classifier, a high-risk profile, which typically included TERT or TP53 mutations, was found in 6% of samples, more frequently BCV-VI. RNA-Seq confirmed ThyroSeq detection of novel RTK fusions in 98.9% of cases. CONCLUSION: In this series, 68% of BCIII-IV nodules were classified as negative by ThyroSeq, potentially preventing diagnostic surgery in this subset of patients. Specific genetic alterations were detected in most BCV-VI nodules, with a higher prevalence of BRAF and TERT mutations and targetable gene fusions compared to BCIII-IV nodules, offering prognostic and therapeutic information for patient management.

Does the presence of capsule influence prognosis in poorly differentiated thyroid carcinoma?

We collected all cases of poorly differentiated thyroid carcinoma at our institution diagnosed between 2007 and 2022 to investigate the role of tumor capsule in these neoplasms along with other histologic factors that may lead to adverse patient outcomes. After the exclusion of those meeting criteria for differentiated high-grade thyroid carcinoma or anaplastic carcinoma, we were left with 65 cases with a poorly differentiated component. Four of those cases (6.2%) were entirely encapsulated with no invasion of the tumor capsule. Unencapsulated tumors showed significantly greater rates of extrathyroidal extension (75.0% versus 41.5%) and death from disease (45.5% versus 12.5%) than encapsulated tumors, regardless of capsular invasion, with no differences in sex, tumor size, angioinvasion, local recurrence, or metastasis. Compared with encapsulated tumors with invasion, encapsulated tumors without capsular invasion showed a strong male predominance (100% versus 38.8%). No encapsulated tumors without capsular invasion demonstrated local recurrence, metastasis, or death from disease. No differences in the percentage of poorly differentiated components were noted among the 3 groups, although there was a trend for encapsulated tumors to have a higher percentage of poorly differentiated components than unencapsulated tumors. We conclude that invasive tumors lacking a capsule demonstrate greater rates of disease-related death despite showing similar adverse histologic features to invasive encapsulated tumors. Moreover, we confirm that encapsulated tumors without capsular invasion have excellent long-term outcomes in terms of recurrences, metastases, and survival.

Salivary gland neoplasms in small biopsies and fine needle aspirations.

Salivary gland neoplasms are rare and represent a diverse group of head and neck tumors. Their diagnosis in limited cellularity specimens can be challenging as many of these have overlapping clinical, radiological presentation, and pathologic features. Fine needle aspiration and/or core biopsies are more of a norm than rarity to be performed preoperatively to provide invaluable information that can guide clinical management including surgery. Even though these limited specimens may not always provide a definitive diagnosis; they have high sensitivity in confirming primary neoplasia, assessing the tumor grade, and ruling out non-surgical disease. An algorithmic pattern based approach can help narrow the differential diagnosis; leading to a definitive diagnosis with the help of specific ancillary studies.

DICER1 RNase IIIb domain mutations trigger widespread miRNA dysregulation and MAPK activation in pediatric thyroid cancer.

DICER1 is a highly conserved RNase III endoribonuclease essential for the biogenesis of single-stranded mature microRNAs (miRNAs) from stem-loop precursor miRNAs. Somatic mutations in the RNase IIIb domain of DICER1 impair its ability to generate mature 5p miRNAs and are believed to drive tumorigenesis in DICER1 syndrome-associated and sporadic thyroid tumors. However, the DICER1-driven specific changes in miRNAs and resulting changes in gene expression are poorly understood in thyroid tissue. In this study, we profiled the miRNA (n=2,083) and mRNA (n=2,559) transcriptomes of 20 non-neoplastic, 8 adenomatous and 60 pediatric thyroid cancers (13 follicular thyroid cancers [FTC] and 47 papillary thyroid cancers [PTC]) of which 8 had DICER1 RNase IIIb mutations. All DICER1-mutant differentiated thyroid cancers (DTC) were follicular patterned (six follicular variant PTC and two FTC), none had lymph node metastasis. We demonstrate that DICER1 pathogenic somatic mutations were associated with a global reduction of 5p-derived miRNAs, including those particularly abundant in the non-neoplastic thyroid tissue such as let-7 and mir-30 families, known for their tumor suppressor function. There was also an unexpected increase of 3p miRNAs, possibly associated with DICER1 mRNA expression increase in tumors harboring RNase IIIb mutations. These abnormally expressed 3p miRNAs, which are otherwise low or absent in DICER1-wt DTC and non-neoplastic thyroid tissues, make up exceptional markers for malignant thyroid tumors harboring DICER1 RNase IIIb mutations. The extensive disarray in the miRNA transcriptome results in gene expression changes, which were indicative of positive regulation of cell-cycle. Moreover, differentially expressed genes point to increased MAPK signaling output and loss of thyroid differentiation comparable to the RAS-like subgroup of PTC (as coined by The Cancer Genome Atlas), which is reflective of the more indolent clinical behavior of these tumors.

Carcinoma Ex Pleomorphic Adenomas: An Institutional Experience and Literature Review.

OBJECTIVES: To provide an institutional experience with cases diagnosed as carcinoma ex pleomorphic adenoma (CXPA), including the cytologic and histologic findings and clinical follow-up, followed by a comparison to the experience documented in the literature. METHODS: We identified cases of CXPA diagnosed at our institution from 2011 to 2021 and reviewed the cytologic and histologic diagnoses, as well as the treatment and clinical outcomes. Additionally, a literature review of the English literature was performed on CXPAs from 2011 to 2021. RESULTS: Forty-one cases of CXPA were identified, with the majority subclassified as adenocarcinoma, not otherwise specified. Five tumors underwent cytogenetic studies and five underwent molecular studies. To date, 36 patients are alive, 8 of whom experienced locoregional recurrence or distant metastasis. CONCLUSIONS: Our institutional experience was comparable to that reported in the literature. Further studies are required to inquire about the role of molecular profiles of CXPAs in clinical risk assessment.

The Impact of the 2022 WHO Classification of Thyroid Neoplasms on Everyday Practice of Cytopathology.

This review outlines how the alterations in the 5th edition of the WHO Classification of Endocrine and Neuroendocrine Tumors of the thyroid gland are likely to impact thyroid cytopathology. It is important to note that WHO subclassifies thyroid tumors into several new categories based on increased comprehension of the cell of origin, pathologic features (including cytopathology), molecular classification, and biological behavior. The 3rd edition of the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) will debut in the near future and will include changes in diagnostic category designations. The changes in the 5th edition of the WHO will in some instances subtly, and in other instances significantly, impact the cytological diagnoses. Moreover, these changes will also affect other thyroid FNA classification schemes used internationally for classifying thyroid FNA specimens.

THADA-IGF2BP3 fusions detected in fine-needle aspiration specimens of thyroid nodules: An institutional experience.

INTRODUCTION: Though the clinical significance of THADA-IGF2BP3 fusions detected in thyroid nodules preoperatively is still under investigation, the limited literature suggests these lesions are clinically low-risk. METHODS: The pathology archives were searched from 2018 to 2022 for all thyroid nodules with a THADA-IGF2BP3 fusion detected via ThyroSeqV3® analysis. Patient demographics and tumor characteristics were collected. Statistical analyses were performed and p < .05 was considered statistically significant. This study was approved by the institutional review board. RESULTS: The case cohort included 34 thyroid nodules with THADA-IGF2BP3 fusions from 32 patients (average age-56.1 years, range: 30-86, male to female ratio-10:22). The average nodule size was 3.2 cm (range: 1.3-7.3 cm). At the time of biopsy, 21 cases were diagnosed as atypia of undetermined significance/follicular lesion of undetermined significance, 12 as follicular neoplasm/suspicious for follicular neoplasm and 1 as suspicious for malignancy. Surgical resection was performed in 29 patients (13 partial and 16 total thyroidectomies) to give a total of 31 nodules. Papillary thyroid carcinoma was diagnosed in 19/31 (61%) cases. No cases showed extrathyroidal extension or lymphovascular invasion. The remaining cases were considered either a low-risk neoplasm or benign. Four cases of NIFTP on final surgical pathology harbored concurrent incidental papillary thyroid microcarcinoma. One patient had the THADA-IGF2BP3 fusion detected in bilateral nodules. CONCLUSIONS: THADA-IGF2BP3 fusions can occur in malignant, low-risk and benign thyroid neoplasms, where malignant neoplasms show lack of aggressive features. Therefore, such entities can be classified as clinically low risk.