DICER1 gene alterations in thyroid diseases

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.

Expanding Our Knowledge of DICER1 Gene Alterations and Their Role in Thyroid Diseases

Mutations in DICER1, a gene involved in RNA interference, have been associated with a wide range of multi-organ neoplastic and non-neoplastic conditions. Historically known for its association with pleuropulmonary blastoma, DICER1 syndrome has received more attention due to the association with newly discovered diseases and tumors. Recent studies evaluating DICER1 mutations and DICER1-driven thyroid disease in both pediatric and adult thyroid nodules revealed thyroid disease as the most common manifestation of DICER1 mutations. This study undertakes a comprehensive investigation into DICER1 mutations, focusing on their role in thyroid diseases. Specific attention was given to thyroid follicular nodular disease and differentiated thyroid carcinomas in infancy as highly indicative of germline DICER1 mutation or DICER1 syndrome. Additionally, poorly differentiated thyroid carcinoma and thyroblastoma were identified as potential indicators of somatic DICER1 mutations. Recognizing these manifestations should prompt clinicians to expedite genetic evaluation for this neoplastic syndrome and classify these patients as high risk for additional multi-organ malignancies. This study comprehensively synthesizes the current knowledge surrounding this genetically associated entity, providing intricate details on histologic findings to facilitate its diagnosis.

Novel pathogenic variant of DICER1 in an adolescent with multinodular goiter, ovarian Sertoli-Leydig cell tumor and pineal parenchymal tumor of intermediate differentiation

OBJECTIVES

To present a case of a new pathogenic variant of DICER1.

CASE PRESENTATION

13-year-old female with non-toxic multinodular goiter and ovarian Sertoli-Leydig cell tumor, in whom a pineal parenchymal tumor of intermediate differentiation was diagnosed. Next-generation sequencing revealed a new germline mutation in the DICER1 gene (exon 16, c2488del [pGlu830Serfs*2] in heterozygosis), establishing the diagnosis of DICER1 syndrome.

CONCLUSIONS

Mutations in the DICER1 gene cause genetic predisposition to a wide spectrum of benign or malignant tumors from childhood to adulthood.

Thyroblastoma: A DICER1-associated embryonal neoplasm and fine needle aspiration diagnostic criteria

Thyroblastoma is a rare, aggressive embryonal thyroid neoplasm associated with DICER1 mutation. It usually presents as a rapidly growing thyroid mass diffusely infiltrating the thyroid lobes and extending into perithyroidal tissue. Most thyroblastomas were initially diagnosed as malignant teratoma or carcinosarcoma. The cytologic features of thyroblastoma have not been well documented. Here, we present the cytological findings of a case of thyroblastoma in a 19-year-old female with a dominant solid left thyroid nodule. A fine needle aspiration biopsy of the mass revealed a highly cellular aspirate composed of crowded, atypical, high nuclear to cytoplasmic ratio epithelial cells, arranged in a variety of architectural patterns including rosette-like microfollicular, solid, and morular. In addition, the background contains a minor population of atypical mesenchymal cells. The cytologic differential diagnosis of thyroblastoma includes primary thyroid neoplasms such as adenomatous nodule, follicular adenoma, follicular carcinoma, and poorly differentiated thyroid carcinoma as well as metastatic carcinoma.

Molecular testing in fine-needle aspiration of thyroid nodules

BACKGROUND

Thyroid nodules are commonly faced by clinicians as palpable nodules or incidentally identified on imaging. Nodules that are found to be suspicious by imaging can be biopsied by fine needle aspiration, which can yield material for molecular testing to refine the diagnosis.

METHODS

The current literature concerning molecular testing in thyroid nodules including available commercial assays was reviewed and summarized.

RESULTS/CONCLUSIONS

Commonly encountered alterations include mutations in RAS, BRAF, TERT promoter, PTEN, and DICER1 as well as fusions of RET, ALK, PAX8-PPARγ, and NTRK. This article provides a summary of these molecular alterations, commercially available molecular assays, and general considerations for thyroid epithelial malignancies and benign thyroid nodules.

Molecular Landscape of Pediatric Thyroid Cancer: A Review

Thyroid carcinomas (TC) are rare in the pediatric population; however, they constitute the most common endocrine malignancy. Despite some similarities with adult carcinomas, they have distinct clinical behavior and responses to therapy due to their unique pathology and molecular characteristics. The age cut-off used for defining the pediatric age group has been variable across different studies, and the universally accepted recommendations influence accurate interpretation of the available data. Moreover, factors such as radiation exposure and germline mutations have greater impact in children than in adults. Papillary TC is the most common and the most evaluated pediatric TC. Others, including follicular, poorly differentiated and medullary carcinomas, are rarer and have limited available literature. Most studies are from the West. Asian studies are primarily from Japan, with few from China, India, Saudi Arabia and Republic of Korea. This review provides a comprehensive account of the well-established and novel biomarkers in the field, including point mutations, fusions, miRNA, and thyroid differentiation genes. Familial and syndromic associations are also discussed. Current management guidelines for pediatric patients are largely derived from those for adults. An awareness of the molecular landscape is essential to acknowledge the uniqueness of these tumors and establish specific diagnostic and therapeutic guidelines.

Primary Thyroid Neoplasm with Fetal Morphology Associated with DICER1 Mutations: Expanding the Diagnostic Profile of Thyroblastoma

Introduction: Thyroblastoma, a primary thyroid neoplasm with histological features of primitive thyroid tissue has recently been described and is included as a distinct entity in the most recent edition of the World Health Organization (WHO) Classification of Tumors (5th edition). In this study, we expand the clinical, morphological, and molecular profile of this aggressive neoplasm. Patient Findings: The patients are females, 19 and 45 years of age, referred for large thyroid nodules. Tumor morphology is biphasic, composed of nests and follicles of epithelial cells, some with colloid-like secretions reminiscent of fetal thyroid follicles intertwined with a primitive stromal spindle cell component. By immunohistochemistry, the epithelial component is diffusely positive for PAX8 and TTF1 markers. Molecular studies showed DICER1 aberrations. Conclusion: A primary primitive thyroid malignancy reminiscent of early fetal embryology with no teratoid element, recently reported as thyroblastoma represents a unique entity, novel in its description, and is likely underdiagnosed.

Overview of the 2022 WHO Classification of Familial Endocrine Tumor Syndromes

This review of the familial tumor syndromes involving the endocrine organs is focused on discussing the main updates on the upcoming fifth edition of the WHO Classification of Endocrine and Neuroendocrine Tumors. This review emphasizes updates on histopathological and molecular genetics aspects of the most important syndromes involving the endocrine organs. We describe the newly defined Familial Cancer Syndromes as MAFA-related, MEN4, and MEN5 as well as the newly reported pathological findings in DICER1 syndrome. We also describe the updates done at the new WHO on the syndromic and non-syndromic familial thyroid diseases. We emphasize the problem of diagnostic criteria, mention the new genes that are possibly involved in this group, and at the same time, touching upon the role of some immunohistochemical studies that could support the diagnosis of some of these conditions. As pathologists play an important role in identifying tumors within a familial cancer syndrome, we highlight the most important clues for raising the suspicious of a syndrome. Finally, we highlight the challenges in defining these entities as well as determining their clinical outcome in comparison with sporadic tumors. Instead of the usual subject review, we present the highlights of the updates on familial cancer syndromes by answering select questions relevant to practicing pathologists.

High Prevalence of DICER1 Mutations and Low Frequency of Gene Fusions in Pediatric Follicular-Patterned Tumors of the Thyroid

Follicular-patterned tumors of the thyroid in the adult population frequently harbor RAS mutations or PAX8-PPARG rearrangement, but little is known about molecular profiles in the pediatric patients with thyroid tumors, which is rare. To identify the molecular profile of pediatric follicular-patterned tumors, we enrolled 41 pediatric patients with follicular-patterned tumors from two institutions. We did next-generation sequencing using a mutation panel targeting 49 thyroid-tumor-related genes and a fusion panel targeting 88 types of thyroid-related gene fusions. We identified nonsynonymous mutations in at least one target gene in most of the tumors (28/41, 68%). Somatic DICER1 mutations (22%, n = 9) were the most common genetic alteration, followed by mutations of NRAS (15%), FGFR3 (15%), PTEN (12%), and STK11 (10%). Infrequent genetic alterations (≤ 5% of all cases) included mutations of HRAS, APC, TSHR, CTNNB1, TP53, EIF1AX, FGFR4, GNAS, RET, and SOS1, and gene fusion of THADA-IGF2BP3. DICER1 and RAS mutations were mutually exclusive. No patients had tumors related to the DICER1 syndrome or the Cowden syndrome. There was no significant difference in total mutation burden or distribution between follicular adenoma and follicular carcinoma. In the literature, the DICER1 mutation has been reported in 20 to 53% of pediatric patients with follicular-patterned tumors. In conclusion, our study reinforces the role of the DICER1 mutation in the development of pediatric thyroid tumors. Gene fusions rarely occur in pediatric follicular-patterned tumors. Mutation or gene fusion alone could not distinguish benign from malignant follicular-patterned tumors in pediatric patients.

Gene of the month: DICER1: ruler and controller

DICER1 is a highly conserved RNaseIII endoribonuclease that has a critical role in the biogenesis of microRNAs (miRNAs). miRNAs are small regulatory RNAs responsible for post-transcriptional gene silencing, controlling more than half of human protein-coding genes. This is achieved through the targeting and regulation of complementary RNA transcripts and has a well-documented role in post-transcriptional gene regulation and transposon repression. DICER1 deficiency results in dysregulation of miRNAs, changing the expression of many genes. DICER1 syndrome represents a collection of benign and malignant tumours arising from an autosomally inherited germline mutation leading to an inherited predisposition to cancer. The syndrome represents an unusual form of Knudson's two-hit hypothesis, where individuals with a pathogenic germline DICER1 variant acquire a second trans-somatic missense DICER1 mutation. This somatic mutation appears to have to occur in one of five hotspots codons and may contribute towards the incomplete penetrance observed within DICER1 syndrome families. In this case, DICER1 is haploinsuffcient with only one deletion required and partial loss of function being advantageous to tumours over complete loss of function. As increasing data emerge reaffirming the pivotal role of DICER1 in the maintenance of human physiology, DICER1 is likely to become an increasingly attractive target for novel therapeutic strategies.