Fetal adenomas and minimally invasive follicular carcinomas of the thyroid frequently display a triploid or near triploid DNA pattern

Aberrant expression of tumor-associated carbohydrate antigen Globo H in thyroid carcinoma

BACKGROUND AND OBJECTIVES

The induction of tumor-associated carbohydrate antigen results from altered glycosylation in transformed cells. Globo H is a hexasaccharide glycosphingolipid overexpressed on malignancies of epithelial origin and has become an attractive vaccine target. We aimed to investigate the expression patterns and prognostic value of Globo H in thyroid neoplasms.

METHODS

Globo H expression was examined by immunohistochemical analysis using commercial and in-house tissue microarrays. The expression was correlated with clinicopathologic characteristics in papillary thyroid cancer.

RESULTS

Normal or benign thyroid lesions were negative for Globo H expression. Globo H was positive in 33% medullary, 24% papillary, 11% undifferentiated, and 8% follicular thyroid cancer. Globo H expression in papillary thyroid cancer was associated with extrathyroidal invasion (P = 0.017), BRAF mutation (P = 0.010), AMES high risk (P = 0.045), and increased ATA risk of recurrence (P = 0.022).

CONCLUSIONS

Globo H is specifically expressed in a subset of thyroid malignancies. In papillary thyroid cancer, Globo H expression is associated with invasiveness and BRAF mutation. Immunotherapy targeting Globo H may have potential applications in thyroid cancer. J. Surg. Oncol. 2016;114:853-858. © 2016 2016 Wiley Periodicals, Inc.

Efficient tumorigenesis by mutation-induced failure to terminate microRNA-mediated adaptive hyperplasia

Seven current contending cancer theories consider different sets of critical events as sufficient for tumorigenesis. These theories, most recently the microRNA dysregulation (MRD) theory, have overlapping attributes and extensive empirical support, but also some discrepancies, and some do not address both benign and malignant tumorigenesis. By definition, the most efficient tumorigenic pathways will dominate under conditions that selectively activate those pathways. The MRD theory provides a mechanistic basis to combine elements of the current theories into a new hypothesis that: (i) tumors arise most efficiently under stress that induces and sustains either protective or regenerative states of adaptive hyperplasia (AH) that normally are epigenetically maintained unless terminated; and (ii) if dysregulated by a somatic mutation that prevents normal termination, these two AH states can generate benign and malignant tumors, respectively. This hypothesis, but not multistage cancer theory, predicts that key participating AH-stem-cell populations expand markedly when triggered by stress, particularly chronic metabolic or oxidative stress, mechanical irritation, toxic exposure, wounding, inflammation, and/or infection. This hypothesis predicts that microRNA expression patterns in benign vs. malignant tumor tissue will correlate best with those governing protective vs. regenerative AH in that tissue, and that tumors arise most efficiently inmutagen-exposed stem cells that either happen to be in, or incidentally later become recruited into, an AH state.

Follicular thyroid carcinoma

Follicular thyroid carcinoma is being diagnosed less and less frequently despite the increasing incidence of well-differentiated thyroid carcinomas everywhere. This review will discuss the reasons underlying such an observation focusing on the evolution of the morphological and immunohistochemical diagnostic criteria of follicular thyroid tumors. It will address the differential diagnosis between follicular carcinoma and three tumor types--follicular adenoma, follicular variant of papillary carcinoma and poorly differentiated carcinoma--as well as the problems raised by the newly described categories of follicular tumors: follicular tumor of uncertain malignant potential, well-differentiated tumor of uncertain malignant potential and well-differentiated carcinoma, not otherwise specified. Finally, the prognostic and therapeutic significance of some promising molecular biomarkers will be discussed within the frame of the aforementioned histopathological classification.

Clinical implications of molecular markers in follicular cell-derived thyroid cancer

The increasing use/applications of molecular biology techniques have provided new insights on the genetic changes that underlie carcinogenesis and tumor progression in thyroid cancer. Molecular analysis may improve the histopathologic evaluation of follicular cell-derived thyroid carcinoma, not only elucidating some unresolved problems related to the diagnosis and disease prognosis, but also by improving patient management. Besides increasing our comprehension of cancer biology, either genetic alterations or gene expression profiles implicated in thyroid carcinogenesis shed new light on innovative diagnostic procedures as well as on targeted therapies.

Intragenic mutations in thyroid cancer

The close genotype-phenotype relationship that characterizes thyroid oncology stimulated the authors to address this article by using a mixed, genetic and phenotypic approach. As such, this article addresses the following aspects of intragenic mutations in thyroid cancer: thyroid stimulating hormone receptor and guanine-nucleotide-binding proteins of the stimulatory family mutations in hyperfunctioning tumors; mutations in RAS and other genes and aneuploidy; PAX8-PPARgamma rearrangements; BRAF mutations; mutations in oxidative phosphorylation and Krebs cycle genes in Hürthle cell tumors; mutations in succinate dehydrogenase genes in medullary carcinoma and C-cell hyperplasia; and mutations in TP53 and other genes in poorly differentiated and anaplastic carcinomas.

B-RAF mutations in the etiopathogenesis, diagnosis, and prognosis of thyroid carcinomas

The very recent discovery of B-RAF point mutations as the most prevalent genetic alteration in papillary thyroid carcinoma has revolutionized the molecular knowledge of thyroid malignancies. In this review, we address the role played by such mutations in the etiopathogenesis, diagnosis, prognosis, and therapy selection of thyroid cancer, with an emphasis on papillary carcinoma.

H-RAS 81 polymorphism is significantly associated with aneuploidy in follicular tumors of the thyroid

Follicular thyroid tumors are often aneuploid. It was advanced that chromosomal instability is closely associated to RAS mutations, but such association remains unproven. H-RAS can be alternatively spliced in two different proteins, p21 and p19, the former being the active protein. In order to investigate the relationship between RAS mutational status and ploidy in thyroid tumors, we analysed RAS genes in a series of 99 follicular lesions (14 nodular goiters, 70 follicular adenomas and 15 follicular carcinomas), eight thyroid carcinoma cell lines and a control group of 102 blood donors, correlating the presence of RAS mutations with the ploidy of the tumors and evaluating the two spliced forms of H-RAS. Overall, 20% of the follicular tumors harbored RAS mutations and 62% of the patients with follicular tumors (and 51% of blood donors) harbored the H-RAS 81T --> C polymorphism. The presence of RAS mutations was not associated with aneuploidy. The H-RAS polymorphism did not seem to confer a higher propensity for neoplastic transformation as it was also found in hyperplastic lesions, but was strongly associated with aneuploidy (P<0.0001). The presence of the H-RAS 81T --> C polymorphism was associated with significantly higher amounts of total H-RAS mRNA expression, higher amounts of p21 isoform and a higher fraction of neoplastic cells in S phase. Our results suggest that the H-RAS 81T --> C polymorphism may induce aneuploidy through overexpression of the active p21 isoform of H-RAS.

Molecular pathology of well-differentiated thyroid carcinomas

The newly discovered molecular features of well-differentiated thyroid carcinomas derived from follicular cells are reviewed, within the frame of the 2004 WHO classification of thyroid tumours, under the following headings: "Follicular carcinoma", "Papillary carcinoma", "Follicular variant of papillary carcinoma" and "Hürthle cell tumours". A particular emphasis is put on the meaning of PAX8-PPARgamma rearrangements, RAS and BRAF mutations, and deletions and mutations of mitochondrial genes and of nuclear genes encoding for mitochondrial enzymes, for thyroid tumorigenesis.

Étude du contenu en ADN nucléaire dans les nodules thyroïdiens

Thyroid nodules are frequent and sometimes they pose a diagnostic and prognostic problem. DNA ploidy study and cell cycle analysis could be of value in the distinction between benign tumors and malignant tumors. Formalin-fixed and paraffin-embedded tissues from 69 patients with different benign and neoplastic lesions were investigated. Nuclear DNA content in thyroid cells was measured after Feulgen staining using SAMBA 200 image analysis system. A diploid DNA stemline was revealed in 75% of histologically proven benign thyroid tumors (15/20) and aneuploidy was found in 57.2% of malignant tumors (28/49). There is a significant correlation between aneuploidy and extra-thyroid extension (p=0.007) and bilateral and/or mediastinal lymph node metastasis (p=0.02). In the majority of benign tumors (19/20), the proliferation index was lower than 3% (< or =3%) however, this index value was higher than 3% (>3%) in more than 83% of malignant tumors (41/49) (p<0.001). The S phase fraction analysis revealed that the threshold of 14% divide the near whole of benign and malignant tumors (p<0.001). Our findings show that in follicular lesions, proliferation index and S phase fraction study appears interesting and helpful in the distinction between benign and malignant tumors, and aneuploidy seems more interesting in prognosis evaluation of these tumors.

Adenomas and follicular carcinomas of the thyroid display two major patterns of chromosomal changes

It was recently shown by flow and static cytometry that a large sub-group of follicular adenomas of the thyroid--fetal/embryonal adenomas--display an aneuploid phenotype. It was also shown that thyroid lesions with a DNA content within the triploid range were either fetal adenomas or follicular carcinomas with a fetal adenoma growth pattern. Follicular tumours with growth patterns other than the so-called fetal adenoma-like pattern were usually diploid or near-diploid. In an attempt to clarify the pattern of chromosomal imbalances in follicular tumours, comparative genomic hybridization (CGH) analysis was performed in a series of 18 follicular neoplasms (ten fetal/embryonal and four common follicular adenomas and four minimally invasive follicular carcinomas). For each tumour, the DNA content was determined by flow cytometry and, in some cases, also by static cytometry. Finally, the copy number of selected chromosomes was determined by interphase fluorescence in situ hybridization (FISH) using centromere probes. With the exception of the single diploid fetal adenoma, all fetal adenomas displayed several DNA copy number changes, with frequent gains of several chromosomes, which were found to be either tetrasomic or trisomic by FISH. This genetic pattern was also present in the single case of follicular carcinoma with aneuploidy and fetal adenoma-like growth pattern. Follicular adenomas other than fetal adenomas, and the remaining follicular carcinomas, showed more losses than gains of chromosomes. These results suggest that follicular tumourigenesis may follow at least two pathways: one characterized by prominent aneuploidy and numerous gains, in which the tumours display a fetal adenoma-like growth pattern; and another accompanied by less obvious aneuploidy or even quasi-diploidy and dominant chromosome losses, in which the tumours display a common follicular architecture.

Comparative analysis of two thyroid tumor cell lines by fluorescence in situ hybridization and comparative genomic hybridization

Tumors and tumor-derived cell lines are typically chromosomally complex and heterogeneous. These features complicate the description of their karyotype. As a first approach to the chromosomal characterization of the two near-triploid thyroid tumor cell lines, BCPAP and FTC133, the techniques of fluorescence in situ hybridization and comparative genomic hybridization were used and compared. Most of the results obtained by the two methods were in good agreement. The follicular-derived cell line FTC133 showed more extensive chromosome variation between cells than the papillary-derived cell line BCPAP. Both cell lines had significant gains in part or whole of chromosomes 1, 11, and 20 and losses in chromosomes 16, 21, and 22. BCPAP cells also had gains in chromosomes 4 and 5 and losses in chromosomes 7, 9, and 10; FTC133 cells had gains in chromosomes 6, 7, 8, 14, 15, and 19. Chromosomes 4 and 5 were the most stable in BCPAP cells; in the FTC133 cells, chromosomes 7 and 19 showed the greatest segregational stability. The results have been discussed in terms of possible karyotype evolution. Moreover, it has been possible to compare the sensitivity limits of the two techniques in the analysis of polyploid tumors.