Well differentiated follicular thyroid neoplasia: impact of molecular and technological advances on detection, monitoring and treatment

Identifying the Carcinogenic Mechanism of Malignant Struma Ovarii Using Whole-Exome Sequencing and DNA Methylation Analysis

Background: Since malignant struma ovarii is a very rare disease, its carcinogenic mechanism has not been elucidated. Here, we sought to identify the genetic lesions that may have led to the carcinogenesis of a rare case of malignant struma ovarii (follicular carcinoma) with peritoneal dissemination. Methods: DNA was extracted from the paraffin-embedded sections of normal uterine tissues and malignant struma ovarii for genetic analysis. Whole-exome sequencing and DNA methylation analysis were then performed. Results: Germline variants of RECQL4, CNTNAP2, and PRDM2, which are tumor-suppressor genes, were detected by whole-exome sequencing. Somatic uniparental disomy (UPD) was also observed in these three genes. Additionally, the methylation of FRMD6-AS2, SESN3, CYTL1, MIR4429, HIF3A, and ATP1B2, which are associated with tumor growth suppression, was detected by DNA methylation analysis. Conclusions: Somatic UPD and DNA methylation in tumor suppressor genes may be associated with the pathogenesis of malignant struma ovarii. To our knowledge, this is the first report of whole-exome sequencing and DNA methylation analysis in malignant struma ovarii. Genetic and DNA methylation analysis may help elucidate the mechanism of carcinogenesis in rare diseases and guide treatment decisions.

Malignant struma ovarii presenting with follicular carcinoma: A case report with molecular analysis

Malignant struma ovarii presenting with follicular carcinoma is extremely rare, and its mechanism of tumorigenesis remains unknown. Here, we present a case of malignant struma ovarii with peritoneal dissemination of follicular carcinoma, for which a molecular analysis for major oncogenic gene alterations in follicular thyroid carcinoma was performed. A 39-year-old nulliparous woman was referred with a diagnosis of highly differentiated follicular carcinoma of ovarian origin. Primary thyroid cancer was not diagnosed, and she had a normal thyroid function. ¹²³I scintigraphy revealed multiple peritoneal dissemination that was surgically resected. Histologically, the tumor consisted of numerous follicles without nuclear features of papillary thyroid carcinoma. Tumor samples were investigated for 50 cancer-related genes, including RAS, BRAF, and p53, and PPARg-PAX8 gene fusion by targeted DNA sequencing and fluorescence in situ hybridization, respectively. No major oncogenic gene alterations were detected. These negative findings suggest a different mechanism of tumorigenesis from that of adult-type follicular thyroid carcinoma.

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Malignant struma ovarii presenting with follicular carcinoma (MSOFC) is rare and often shows long-latency recurrence.

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Detailed molecular investigation of MSOFC was firstly performed to identify its specific molecular characteristics.

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Lack of common molecular alterations suggests MSOFC may have different tumorigenesis from that of adult thyroid counterpart.

Genomic Characterization of Differentiated Thyroid Carcinoma

Since the release of The Cancer Genome Atlas study of papillary thyroid carcinoma (PTC) in 2014, additional genomic studies of differentiated thyroid carcinoma (DTC) using massively-parallel sequencing (MPS) have been published. Recent advances in MPS technology have started to provide important insights into the molecular pathogenesis of DTC. In the genomic landscape, the most recurrently altered genes in DTC, which has a low mutational burden relative to other cancers, are BRAF, RAS, and fusion genes. Some novel driver candidates also have been identified. The frequency of these genomic alterations varies across the subtypes of DTC (classical PTC, follicular variant of PTC, and follicular thyroid carcinoma). Telomerase reverse transcriptase (TERT) promoter mutations are the alteration that makes the most important contribution to the progression of DTC. In the transcriptomic landscape, DTC can be classified according to its gene expression profile, and each subtype has a distinct mutational profile, intracellular signaling output, and clinicopathological characteristics. Herein, we review the results of genomic studies using MPS technology, and describe the types and frequencies of genomic alterations according to histological classifications of DTC and the characteristics and significance of the gene expression signatures of DTC.

New developments in the diagnosis and treatment of thyroid cancer

Thyroid cancer exists in several forms. Differentiated thyroid cancers include those with papillary and follicular histologies. These tumors exist along a spectrum of differentiation, and their incidence continues to climb. A number of advances in the diagnosis and treatment of differentiated thyroid cancers now exist. These include molecular diagnostics and more advanced strategies for risk stratification. Medullary cancer arises from the parafollicular cells and not the follicular cells. Therefore, diagnosis and treatment differs from those of differentiated thyroid tumors. Genetic testing and newer adjuvant therapies have changed the diagnosis and treatment of medullary thyroid cancer. This review will focus on the epidemiology, diagnosis, workup, and treatment of both differentiated and medullary thyroid cancers, focusing specifically on newer developments in the field.

RAS mutations in thyroid cancer

In recent years, our understanding of the genetic alterations underlying thyroid oncogenesis has greatly expanded. The use of molecular markers, including RAS, in the management of thyroid carcinoma is also increasing. This review summarizes the current literature surrounding RAS and discusses its potential as a diagnostic and prognostic indicator in the management of thyroid cancer.