The molecular diagnosis and management of thyroid neoplasms. Curr Opin Oncol. 2012;24:35-41. [PMID: 22123232 DOI: 10.1097/cco.0b013e32834dcfca]

Genetic Considerations in the Tumorigenesis, Diagnosis, and Treatment of Differentiated Thyroid Cancer: Current State of the Science

Thyroid nodules remain a common diagnosis encountered in general and endocrine surgical practice, and thyroid cancer appears to be increasing in incidence in both the United States and worldwide. The understanding of the complex genetics surrounding thyroid neoplasia has increased substantially in recent years and, consequently, has become a consideration in risk stratification, diagnosis, prognosis, and treatment. Molecular genetic analysis of thyroid nodules is now a readily available technology for diagnostic purposes via analysis of fine-needle aspiration biopsy (FNAB) specimens. Although their routine use is controversial, they may aid in selecting which patients require surgery and those who may be safely observed. In the following review, the genetics of the tumorigenesis of thyroid cancer are reviewed, focusing on the most common and clinically relevant of the literally hundreds of known mutations. Following this, the current status of the use of genetic analysis and molecular diagnostics in the workup of thyroid nodules and the diagnosis of differentiated thyroid cancer is explored. Finally, evolving concepts relating to the use of thyroid cancer genetics in individualizing treatment planning, follow-up, and management of recurrent disease is discussed. The goal is to provide the general surgeon with a working knowledge of the most common genetic alterations present in differentiated thyroid cancer, their relevance in clinical practice, and how they impact prognosis and treatment.

DNA microarray-based resonance light scattering assay for multiplexed detection of DNA mutation in papillary thyroid cancer

A DNA microarray-based resonance light scattering assay has been developed for multiplexed detection of papillary thyroid carcinoma (PTC) related genic mutation.

PREDICTIVE VALUE OF SOMATIC MUTATIONS FOR THE DEVELOPMENT OF MALIGNANCY IN THYROID NODULES BY CYTOPATHOLOGY

OBJECTIVE

The purpose of our prospective longitudinal study was to evaluate the predictive efficacy of genetic testing for malignancies in fine-needle aspiration biopsy samples that are cytologically benign at the time of biopsy.

METHODS

A total of 779 aspirated cytological samples collected from thyroid nodules of 626 patients were included in a 3-year follow-up study. Consecutive patients with cytologically benign thyroid nodules by the Bethesda System for Reporting Thyroid Cytopathology were enrolled in the study. At enrollment, somatic 1-point nucleotide polymorphisms of BRAF and RAS family genes were tested by melting-point analysis, while RET/PTC and PAX8/PPAR-gamma rearrangements were examined by real-time polymerase chain reaction. The genetic test was considered to be positive if a somatic mutation was found. Malignant cytopathologic diagnoses were confirmed by histopathology.

RESULTS

In samples collected from 779 thyroid nodules, there were 39 BRAF, 33 RAS mutations, and 1 RET/PTC rearrangements found at the beginning of the study. No PAX8/PPAR-gamma rearrangement was identified. There were 52 malignant thyroid tumors removed during follow-up, out of which 24 contained a somatic mutation. The specificity of the presence of somatic mutations for malignancies was as high as 93.3%, and sensitivity was 46.2%. The negative predictive value of genetic testing reached 96.0%.

CONCLUSION

Our results show that our set of genetic tests can predict the appearance of malignancy in benign thyroid nodules (at the beginning of follow-up) with high specificity and strong negative predictive value.

ABBREVIATIONS

BRAF = v-raf murine sarcoma viral oncogene homolog B1 FLUS = follicular lesion of undetermined significance FNAB = fine-needle aspiration biopsy FTC = follicular thyroid carcinoma HRAS = homologous to the oncogene from the Harvey rat sarcoma virus KRAS = homologous to the oncogene from the Kirsten rat sarcoma virus NRAS = first isolated from a human neuroblastoma/neuroblastoma RAS = viral oncogene homolog PAX8 = paired box 8 PCR = polymerase chain reaction PPAR-gamma = peroxisome proliferator-activated receptor gamma PTC = papillary thyroid carcinoma RAS = rat sarcoma RET = rearranged during transfection tyrosine-kinase proto-oncogene SM = somatic mutation SNP = single-nucleotide polymorphism.

Cytopathologic diagnosis of fine needle aspiration biopsies of thyroid nodules

Fine-needle aspiration (FNA) cytology is an important diagnostic tool in patients with thyroid lesions. Several systems have been proposed for the cyropathologic diagnosis of the thyroid nodules. However cases with indeterminate cytological findings still remain a matter of debate. In this review we analyze all literature regarding Thyroid Cytopathology Reporting systems trying to identify the most suitable methodology to use in clinical practice for the preoperative diagnosis of thyroid nodules. A review of the English literature was conducted, and data were analyzed and summarized and integrated from the authors’ perspective. The main purpose of thyroid FNA is to identify patients with higher risk for malignancy, and to prevent unnecessary surgeries for benign conditions. The Bethesda System for Reporting Thyroid Cytopathology is the most widely used system for the diagnosis of thyroid FNA specimens. This system also contains guidelines for the diagnosis and treatment of indeterminate or suspicious for malignancy cases. In conclusion, patients who require repeated FNAs for indeterminate diagnoses will be resolved by repeat FNA in a percentage of 72%-80%.

The impact of CLAUDIN-1 on follicular thyroid carcinoma aggressiveness

CLAUDIN-1 belongs to the family of transmembrane tight junction proteins tightening the paracellular cleft of epithelial cells. In human malignancies, CLAUDIN-1 is often dysregulated and located in subcellular compartments, particularly in the nucleus where it may influence cellular behaviour. Here, we studied CLAUDIN-1 in relation to the biological characteristics of follicular thyroid carcinoma (FTC). CLAUDIN-1 immuno-staining showed loss of membrane expression and increased nuclear CLAUDIN-1 localization in FTC metastases. CLAUDIN-1 function was further investigated in two different follicular thyroid carcinoma cell lines: FTC-133 isolated from a regional lymph node metastasis and FTC-238 derived from a lung metastasis. In both cell lines CLAUDIN-1 expression was demonstrated in the cell nuclei with a significantly higher protein expression in FTC-238 compared to FTC-133 cells. Interestingly, in vitro scratch assay revealed enriched nuclear CLAUDIN-1 expression near the scratch. Furthermore, the increase of the pathogenic character of FTC-133 cells by RASV12 transfection was associated with elevated CLAUDIN-1 expression and enhanced cell migration, invasion and proliferation. Likewise over-expression of nuclear CLAUDIN-1 in FTC-133 cells resulted in increased cell migration and invasion. Conversely, CLAUDIN-1 downregulation in FTC-238 cells by siRNA resulted in decreased cell migration and invasion and was accompanied by reduced phosphoPKC expression. Moreover, activation and inhibition of PKC resulted in CLAUDIN-1 up- and downregulation in FTC cells respectively. These data suggest an impact of CLAUDIN-1 on follicular thyroid carcinoma aggressiveness, which could potentially be influenced by PKC activity.

miR-145 suppresses thyroid cancer growth and metastasis and targets AKT3

The expression and function of miR-145 in thyroid cancer is unknown. We evaluated the expression and function of miR-145 in thyroid cancer and its potential clinical application as a biomarker. We found that the expression of miR-145 is significantly downregulated in thyroid cancer as compared with normal. Overexpression of miR-145 in thyroid cancer cell lines resulted in: decreased cell proliferation, migration, invasion, VEGF secretion, and E-cadherin expression. miR-145 overexpression also inhibited the PI3K/Akt pathway and directly targeted AKT3. In vivo, miR-145 overexpression decreased tumor growth and metastasis in a xenograft mouse model, and VEGF secretion. miR-145 inhibition in normal primary follicular thyroid cells decreased the expression of thyroid cell differentiation markers. Analysis of indeterminate fine-needle aspiration samples showed miR-145 had a 92% negative predictive value for distinguishing benign from malignant thyroid nodules. Circulating miR-145 levels were significantly higher in patients with thyroid cancer and showed a venous gradient. Serum exosome extractions revealed that miR-145 is secreted. Our findings suggest that miR-145 is a master regulator of thyroid cancer growth, mediates its effect through the PI3K/Akt pathway, is secreted by the thyroid cancer cells, and may serve as an adjunct biomarker for thyroid cancer diagnosis.

BRAF genetic heterogeneity in papillary thyroid carcinoma and its metastasis

Intratumoral heterogeneity is widely recognized as an important determinant of a cancer's initial response and its subsequent resistance to targeted therapy. BRAF V600E mutation, common in papillary thyroid carcinoma (PTC), is helpful in fine needle aspiration diagnosis of thyroid nodules and is being evaluated for targeted therapies. This study was designed to assess the presence of BRAF mutation heterogeneity within primary PTCs and between paired primary and metastatic lesions. Genetic heterogeneity was evaluated in 47 PTCs (38 differentiated papillary thyroid carcinomas and 9 poorly differentiated PTCs with anaplastic areas). The differentiated papillary thyroid carcinomas included 16 cases with regional lymph node metastases at thyroidectomy and 9 cases with recurrent metastases to regional lymph nodes more than 5 years post thyroidectomy. Genetic heterogeneity of BRAF was studied by comparing the mutation status in different samples of tumor as follows: (a) 2 separate areas (each >1.5 cm in diameter) within the primary tumor, (b) a more than 1.5 cm area of primary carcinoma and a second 5 mm area simulating a fine needle aspiration sample from a different portion of the primary tumor, (c) primary carcinoma and its lymph node metastasis at thyroidectomy, (d) primary carcinoma and the recurrent metastasis, and (e) differentiated and anaplastic areas in the primary carcinoma. BRAF mutation status was concordant in 95.2% of the 62 paired samples. Discordant BRAF status was detected in only 4.8% of the pairs studied and most frequently involved cases with recurrent metastasis thus suggesting a need for additional testing of these lesions before instituting therapy.

Aggressive variants of papillary thyroid microcarcinoma are associated with extrathyroidal spread and lymph-node metastases: a population-level analysis

BACKGROUND

Tall cell variant (TCV) and diffuse sclerosing variant (DSV) of papillary thyroid cancer are aggressive subtypes, for which tumors ≤1 cm have not been exclusively studied.

METHODS

The SEER database (1988-2009) was used to compare characteristics of TCV ≤1 cm (mTCV) and DSV ≤1 cm (mDSV) with classic papillary thyroid microcarcinoma (mPTC). Survival was analyzed with the Kaplan-Meier method and log-rank test, and risk factors for nodal metastases with chi-square analysis and binary logistic regression.

RESULTS

There were 97 mTCV, 90 mDSV, and 18,260 mPTC patients. mTCV incidence increased by 79.9% (p=0.153) over the study period, while mDSV incidence decreased by 10.3% (p=0.315). Compared to classic mPTC, mTCV tended to be larger on average (7.1 mm vs. 5.3 mm, p<0.001), with higher rates of multifocality (47.2% vs. 34.0% respectively, p=0.018) and lymph-node examination (63.9% vs. 39.2% respectively, p<0.001), while in mDSV, nodal metastases were more frequent (57.1% vs. 33.1% respectively, p=0.007). Both aggressive variants had higher rates of extrathyroidal extension (27.8% mTCV vs. 13.3% mDSV vs. 6.1% mPTC, p<0.001). Aggressive variants also received radioactive iodine more frequently (39.2% mTCV vs. 40.0% mDSV vs. 29.1% mPTC, p<0.001). However, they were not statistically more likely to receive thyroidectomy over lobectomy compared to classic mPTC. There were no significant differences in overall and disease-specific survival between the histologies. In mTCV, after adjustment, extrathyroidal extension was independently associated with size >7 mm (odds ratio (OR) 4.4 [CI 1.5-13.6]) and nodal metastasis with multifocality (OR 5.4 [CI 1.3-23.4]) and extrathyroidal extension (OR 5.8 [CI 1.3-25.4]). No statistically significant predictors of extrathyroidal extension or nodal metastasis in mDSV were observed.

CONCLUSIONS

Aggressive variants of mPTC tend to exhibit more aggressive pathologic characteristics than classic mPTC, but survival appears to be similar. Treatment with total thyroidectomy and central lymphadenectomy may be warranted if the diagnosis can be made pre- or intraoperatively.

Five Top Stories in Cytopathology

Context.—Cytology relies heavily on morphology to make diagnoses, and morphologic criteria have not changed much in recent years. The field is being shaped predominantly by new techniques for imaging and for acquiring and processing samples, advances in molecular diagnosis and therapeutics, and regulatory issues.

Objective.—To review the importance of classical morphology in the future of cytopathology, to identify areas in which cytology is expanding or contracting in its scope, and to identify factors that are shaping the field.

Data Sources.—Literature review.

Conclusions.—Five stories paint a picture in which classical cytomorphology will continue to have essential importance, both for diagnosis and for improving our understanding of cancer biology. New endoscopy and imaging techniques are replacing surgical biopsies with cytology samples. New molecularly targeted therapies offer a chance for cytology to play a major role, but they pose new challenges. New molecular tests have the potential to synergize with, but not replace, morphologic interpretation of thyroid fine-needle aspirations. Ultrasound-guided fine-needle aspiration performed by cytopathologists is opening a new field of “interventional cytopathology” with unique value. For the productive evolution of the field, it will be important for cytopathologists to play an active role in clinical trials that document the ability of cytology to achieve cost-effective health care outcomes.

Rapid detection of K-, N-, H-RAS, and BRAF hotspot mutations in thyroid cancer using the multiplex primer extension

OBJECTIVES

The objective of this study is to develop a multiplex PCR and primer extension to detect K-, N-, H-RAS, and BRAF mutations.

DESIGN AND METHODS

DNA samples were isolated from 76 thyroid cancer patients. Multiplex amplification of exons 2 and 3 of three RAS genes and exon 15 of the BRAF gene using three pairs of primers was performed in a single tube. The products were split into three tubes. First, we used nine different-sized N-RAS and BRAF primers to detect base changes in N-RAS and BRAF. The other two tubes used seven separate different-sized K-RAS and H-RAS primers to detect base changes.

RESULTS

We compared these results with direct sequencing. The two methods generated identical results, but our method was superior to direct sequencing in terms of the amount of work and time involved.

CONCLUSIONS

We present a rapid method to detect mutations of K-, N-, H-RAS, and BRAF in human cancers.

Progress in molecular-based management of differentiated thyroid cancer

Substantial developments have occurred in the past 5-10 years in clinical translational research of thyroid cancer. Diagnostic molecular markers, such as RET-PTC, RAS, and BRAF(V600E) mutations; galectin 3; and a new gene expression classifier, are outstanding examples that have improved diagnosis of thyroid nodules. BRAF mutation is a prognostic genetic marker that has improved risk stratification and hence tailored management of patients with thyroid cancer, including those with conventionally low risks. Novel molecular-targeted treatments hold great promise for radioiodine-refractory and surgically inoperable thyroid cancers as shown in clinical trials; such treatments are likely to become a component of the standard treatment regimen for patients with thyroid cancer in the near future. These novel molecular-based management strategies for thyroid nodules and thyroid cancer are the most exciting developments in this unprecedented era of molecular thyroid-cancer medicine.