Summary statement: utility of molecular marker testing in thyroid cancer

False-negative Results with the Bethesda System of Reporting Thyroid Cytopathology: Predictors of Malignancy in Thyroid Nodules Classified as Benign by Cytopathologic Evaluation

The benign category of the Bethesda System for reporting thyroid cytopathology (BSRTC) predicts an incidence of malignancy from zero to three per cent. However, recent series report higher rates of malignancy ranging from eight to 14 per cent. Surgery is often performed for reasons other than their fine needle aspiration biopsy (FNAB) such as symptoms, nodule enlargement, or worrisome imaging. We hypothesized that an analysis of patients who underwent thyroidectomy despite a benign FNAB would identify predictors of malignancy, an area not currently addressed by American Thyroid Association guidelines. We performed a retrospective analysis of patients with benign FNAB results who underwent thyroidectomy from October 2007 to October 2012. Data collected included symptoms, imaging findings, FNAB results, and operative and histopathology results, all of which were obtained by chart review. Findings were compared between patients with and without a diagnosis of malignancy. Statistical significance was set as P < 0.05. Of 3839 FNABs, 2838 were benign. Of these, 180 underwent surgery for indications other than the FNAB category. Twenty-four (13.4%) malignancies were identified: 12 (6.7%) incidental microcarcinomas and 12 (6.7%) significant cancers (papillary greater than 1.0 cm, any nonpapillary histology). No patient's symptoms or signs reached significance as a predictor of malignancy. Suspicious ultrasound appearance was significantly associated with an underlying carcinoma ( P = 0.004). The false-negative result with benign FNAB is higher in surgical series than suggested by the BSRTC. Patients with tolerable symptoms may be observed in the face of a benign FNAB. Additionally, despite a benign FNAB, recommendations for closer follow-up or surgical intervention are warranted if the ultrasound appearance is suspicious.

The utility of the Bethesda category and its association with BRAF mutation in the prediction of papillary thyroid cancer stage

PURPOSE

This study aims to determine the utility of the Bethesda category and its association with BRAF mutation in prediction of the papillary thyroid cancer (PTC) stage.

METHODS

A prospective study analyzed patients who had ultrasound-suspicious thyroid nodules, underwent FNA and cytological examination, and were classified according to the Bethesda system. Patients from Undetermined Significance Or Follicular Lesion Of Undetermined Significance (AUS/FLUS), Follicular Neoplasm or Suspicious for a Follicular Neoplasm (FN/SFN), Suspicious for Malignant Cells (SMC), and Positive for Malignant Cells (PMC) groups were examined for the BRAF mutation and had a thyroid surgery. Demographical and histological features and stage of the disease were evaluated for PTC patients in accordance with the Bethesda category and its association with BRAF mutation.

RESULTS

Three hundred eight of all patients underwent operation. One hundred forty-three (46.4%) of them were diagnosed with PTC. In 14 (9.8%) PTC cases, FNA biopsies were classified as AUS/FLUS, 23 (16.1%) as FN/SFN, 41 (28.7%) as SMC, and 65 (45.5%) as PMC. I-II stages of PTC were diagnosed for 88 (61.5%) patients and III-IVA for 55 (38.5%). Patients from the SMC and PMC groups had larger tumors, higher incidence of lymph node metastases, classical PTC type, B-type Raf (BRAF) positive, and III-IVA stage cancer, than patients from the AUS/FLUS and FN/SFN groups. When comparing 27 (18.9%) BRAF-negative patients from the AUS/FLUS and FN/SFN groups with 116 (81.1%) BRAF-negative patients from the SMC and PMC groups and all BRAF-positive patients, the prediction of more aggressive histological features and stage was slightly improved.

CONCLUSIONS

Higher Bethesda categories are associated with higher stages of PTC. Association of the Bethesda category with BRAF mutation can slightly improve the value of stage prediction.

Correlation Between Histological Diagnosis and Mutational Panel Testing of Thyroid Nodules: A Two-Year Institutional Experience

BACKGROUND

Indeterminate thyroid fine-needle aspiration (FNA) cytology, including atypia of undetermined significance (AUS/FLUS) and suspicious for follicular neoplasm (SFN), continues to generate uncertainty about the presence of malignancy, resulting in repeated follow-up, repeat FNA, or diagnostic surgery. Mutational panel testing may improve the malignancy risk prediction in indeterminate nodules, but the general application of such testing has not been investigated extensively.

METHODS

A retrospective review was performed of all patients undergoing thyroidectomy at a tertiary care facility over a two-year period. Mutational panel test results, when present, were analyzed relative to FNA cytologic result and surgical histopathologic diagnosis. Malignancy rates, sensitivity, specificity, positive predictive values (PPV), negative predictive values (NPV) and positive and negative likelihood ratios (LR) were calculated.

RESULTS

A total of 261 operated thyroid nodules had the following initial FNA cytology results: 2% non-diagnostic, 23% benign, 28% AUS/FLUS, 11% SFN, 9% suspicious for malignancy (SUSP), and 27% malignant. The histopathologic malignancy rate was 48%, subcategorized by cytology into benign 7%, AUS/FLUS 30%, SFN 38%, and SUSP 83%. Mutations were more frequent in indeterminate nodules that were histologically malignant versus benign (p < 0.0001) or versus adenoma (p = 0.001). Mutational analysis in 44 AUS/FLUS nodules resulted in a malignancy detection sensitivity of 85%, a specificity of 65%, a PPV of 50%, a NPV of 91%, and a positive LR of 2.4. In 12 SFN nodules analyzed with ThyroSeq(®) testing, sensitivity was 100%, specificity 57%, PPV 63%, NPV 100%, and LR 2.3. Performance of the seven-gene mutational panel was not significantly different from the ThyroSeq(®) panel in the AUS/FLUS group. The malignancy yield, comparing the mutation positive AUS/FLUS group with the untested AUS/FLUS surgical cohort, did not reach statistical significance (p = 0.17).

CONCLUSIONS

In a surgical cohort, a similar NPV but a lower PPV was found with the use of mutational panel testing compared to the published literature. Following the identification of a mutation, the prevalence of malignancy in the AUS/FLUS or SFN category was increased by nearly 15% to 45% and 53%, respectively. Further study is needed to confirm these results and to analyze clinical outcome subcategories relative to the utility of mutational testing.

Sonographic Appearance is Useful in Predicting the Extent of Initial Operative Therapy for Thyroid Nodules Classified as “Suspicious for Malignancy”

The “suspicious for malignancy” (SFM) category of the Bethesda system for reporting thyroid cytopathology predicts an incidence of malignancy from 60 to 75 per cent. Recommended treatment is via either lobectomy or total/near total thyroidectomy. Identification of predictors of malignancy in this category would be useful in selecting the extent of operative therapy in these patients. Published literature has suggested that suspicious ultrasound (US) findings are useful in predicting malignancy in both the “benign,” “atypia of uncertain significance/follicular lesion of uncertain significance,” and “suspicious for follicular neoplasm” categories. We hypothesized that US would be similarly useful in patients with nodules classified as SFM. We performed a retrospective analysis of patients with fine needle aspiration biopsy (FNAB) classified as SFM who underwent thyroidectomy from October 2007 to October 2012. Data collected included symptoms, suspicious imaging findings, FNAB results, and histopathology results—all obtained via chart review. Findings were compared between patients with/without a diagnosis of thyroid malignancy. Significance was set at P < 0.05. Of 3839 FNAB, 53 were classified as SFM. Of these, 36 were available for review. Twenty-four (66.7%) carcinomas were identified—19 papillary, 3 follicular variant of papillary, 1 follicular, and 1 medullary. No symptoms/signs reached significance as a predictor of malignancy. A suspicious US appearance, however, was significantly associated with an underlying carcinoma ( P = 0.002). Patients with a Bethesda system for reporting thyroid cytopathology report of SFM and suspicious US findings are statistically more likely to harbor an underlying malignancy. This information is useful in selecting which patients are most likely to benefit from total/near total thyroidectomy as opposed to lobectomy as the initial operative strategy.

BRAF(V600E) Mutation, RET/PTC1 and PAX8-PPAR Gamma Rearrangements in Follicular Epithelium Derived Thyroid Lesions - Institutional Experience and Literature Review

BACKGROUND

Thyroid cancers are the most frequently occurring endocrine malignancy worldwide. In Turkey, thyroid cancers are ranked 2(nd) on the incidence list in women, with a rate of 16.2%, but they are not included among the top 10 cancer types in men.

AIMS

To identify the contribution of the BRAF(V600E) mutation, and the RET/PTC1 and PAX8-PPARγ rearrangements in the diagnosis and differential diagnosis of follicular epithelial-derived thyroid lesions.

STUDY DESIGN

Retrospective clinical and molecular genetic study.

METHODS

A total of 86 thyroid cases diagnosed between 2001 and 2012 at the Department of Pathology were included in the retrospective study group. Samples best representing the lesion and comprising capsules were chosen in the selection of paraffin blocks pertaining to the cases. The BRAF(V600E) mutation, and the RET/PTC1 and PAX8-PPARγ rearrangements were investigated in all cases.

RESULTS

The BRAF(V600E) mutation was observed in 12 out of 37 papillary carcinoma cases (32.4%), in 1 out of 15 follicular carcinoma cases (6.6%), and in 1 out of 7 undifferentiated carcinoma cases (14.3%). No mutation was detected in benign lesions. The RET/PTC1 rearrangement was detected in 2 out of 7 undifferentiated carcinoma cases (28.6%), and in 1 out of 15 follicular carcinoma cases (6.6%). No gene rearrangement was detected in benign lesions. The PAX8-PPARγ rearrangement was detected in 5 out of 15 follicular thyroid carcinoma cases (33.3%) and in 1 out of 15 follicular adenoma cases (6.6%).

CONCLUSION

The BRAF(V600E) mutation and RET/PTC1 rearrangement were effective in distinguishing the follicular epithelium-derived benign and malignant lesions of the thyroid in the resection materials. The BRAF(V600E) mutation was rather specific to papillary carcinoma in the thyroid, and in cases where the BRAF(V600E) mutation was detected, multi-centricity, lymph node metastasis and capsular invasion findings were observed more frequently compared to cases in which no mutation was observed. The PAX8-PPARγ rearrangement was observed to be more effective in the differentiation of adenomas and carcinomas in follicular neoplasms of the thyroid, whereas the RET/PTC1 analysis contributed to the differential diagnosis of papillary carcinoma histogenesis at a frequency of 29% in undifferentiated thyroid carcinomas.

Additional BRAF mutation analysis may have additional diagnostic value in thyroid nodules with "suspicious for malignant" cytology alone even when the nodules do not show suspicious US features

The BRAF(V600E) mutation test has been more effective in thyroid nodules with suspicious US features than ones without suspicious features. Therefore, we investigated the role of the BRAF(V600E) mutation as an additional study to cytology in diagnosing a thyroid nodule without suspicious US features. This study was performed at Severance hospital from December 2010 through February 2012. During this period, 2,650 patients with 2,918 nodules underwent FNA with an additional BRAF(V600E) mutation test. Among them, we excluded thyroid nodules with suspicious US features. Finally, 485 thyroid nodules in 466 patients (mean age 50.3 years; range 9-80 years) were included in this study. We compared the differences between patients with malignant and benign thyroid nodules. We evaluated the detection rates of the BRAF(V600E) mutation according to the Bethesda System for Reporting Thyroid Cytopathology (BSRTC). There were 60 (60/485, 12.4 %) malignant and 425 (425/485, 87.6 %) benign nodules. The detection rate of the BRAF(V600E) mutation in thyroid nodules without suspicious US features was only 6.6 % (32/485). Most had malignant cytology (62.5 %, 20/32). For nodules without malignant cytology, only 12 nodules (2.6 %, 12/462) had the BRAF mutation. Among the 12 nodules, nine nodules were suspicious for malignancy on cytology. Additional BRAF mutation analysis shows additional diagnostic value in thyroid nodules with "suspicious for malignant" cytology alone even when the nodules do not show suspicious US features. Therefore, the test should be selectively performed in thyroid nodules without suspicious US features, considering cost-effectiveness as well as diagnostic accuracy.

False-negative results with the Bethesda System of reporting thyroid cytopathology: predictors of malignancy in thyroid nodules classified as benign by cytopathologic evaluation

The benign category of the Bethesda System for reporting thyroid cytopathology (BSRTC) predicts an incidence of malignancy from zero to three per cent. However, recent series report higher rates of malignancy ranging from eight to 14 per cent. Surgery is often performed for reasons other than their fine needle aspiration biopsy (FNAB) such as symptoms, nodule enlargement, or worrisome imaging. We hypothesized that an analysis of patients who underwent thyroidectomy despite a benign FNAB would identify predictors of malignancy, an area not currently addressed by American Thyroid Association guidelines. We performed a retrospective analysis of patients with benign FNAB results who underwent thyroidectomy from October 2007 to October 2012. Data collected included symptoms, imaging findings, FNAB results, and operative and histopathology results, all of which were obtained by chart review. Findings were compared between patients with and without a diagnosis of malignancy. Statistical significance was set as P < 0.05. Of 3839 FNABs, 2838 were benign. Of these, 180 underwent surgery for indications other than the FNAB category. Twenty-four (13.4%) malignancies were identified: 12 (6.7%) incidental microcarcinomas and 12 (6.7%) significant cancers (papillary greater than 1.0 cm, any nonpapillary histology). No patient's symptoms or signs reached significance as a predictor of malignancy. Suspicious ultrasound appearance was significantly associated with an underlying carcinoma (P = 0.004). The false-negative result with benign FNAB is higher in surgical series than suggested by the BSRTC. Patients with tolerable symptoms may be observed in the face of a benign FNAB. Additionally, despite a benign FNAB, recommendations for closer follow-up or surgical intervention are warranted if the ultrasound appearance is suspicious.

Genetic mutations, molecular markers and future directions in research

Recent molecular studies have described a number of abnormalities associated with the pathogenesis of thyroid carcinoma. These distinct molecular events are often associated with specific stages of tumor development and may serve as prognostic factors and therapeutic targets. A better understanding of the mechanisms involved in thyroid cancer pathogenesis, will hopefully help translate these discoveries to improved patient care.

DNA copy number variations characterize benign and malignant thyroid tumors

CONTEXT

Fine-needle aspiration (FNA) is the best diagnostic tool for preoperative evaluation of thyroid nodules but is often inconclusive as a guide for surgical management.

OBJECTIVE

Our hypothesis was that thyroid tumor subtypes may show characteristic DNA copy number variation (CNV) patterns, which may further improve the preoperative classification.

DESIGN

Our study cohorts included benign follicular adenomas (FAs), classic papillary thyroid carcinomas (PTCs), and follicular variant PTCs (FVPTCs), the three subtypes most commonly associated with inconclusive preoperative cytopathology.

SETTING

Tissue and FNA samples were obtained at an academic tertiary referral center.

PATIENTS

Cases were identified that underwent partial or complete thyroidectomy for malignant or indeterminate thyroid lesions between 2000 and 2008 and had adequate snap-frozen tissue.

INTERVENTIONS

Pairs of tumor tissue and matching normal thyroid tissue-derived DNA were compared using 550K single-nucleotide polymorphism arrays.

MAIN OUTCOME MEASURE

Statistically significant differences in CNV patterns between tumor subtypes were identified.

RESULTS

Segmental amplifications in chromosomes (Ch) 7 and 12 were more common in FAs than in PTCs or FVPTCs. Additionally, a subset of FAs and FVPTCs showed deletions in Ch22. We identified the 5 CNV-associated genes best at discriminating between FAs and PTCs/FVPTCs, which correctly classified 90% of cases. These 5 Ch12 genes were validated by quantitative genomic PCR and gene expression array analyses on the same patient cohort. The 5-gene signature was then successfully validated against an independent test cohort of benign and malignant tumor samples. Finally, we performed a feasibility study on matched FA-derived intraoperative FNA samples and were able to correctly identify FAs harboring the Ch12 amplification signature, whereas FAs without amplification showed a normal Ch12 signature.

CONCLUSIONS

Thyroid tumor subtypes possess characteristic genomic profiles that may further our understanding of structural genetic changes in thyroid tumor subtypes and may lead to the development of new diagnostic biomarkers in FNA samples.

Platelet-derived growth factor receptor-α promotes lymphatic metastases in papillary thyroid cancer

Lymph node metastases are common in papillary thyroid cancer (PTC) and can be resistant to surgical extirpation or radioiodine ablation. We examined the role of platelet-derived growth factor receptor (PDGFR) in mediating lymph node metastases in PTC. Clinical specimens of PTC (n = 137) were surveyed in a tissue array and by western blots to examine the relationship between expression of the α and β subunits of PDGFR and lymph node metastases. PDGFR-α was found at high levels in primary tumours with known lymphatic metastases but not in those tumours lacking nodal involvement (p < 0.0001). However, PDGFR-β expression was not linked to metastatic disease (p = 0.78) as it was found in virtually all PTC specimens. A matching analysis in fresh PTC specimens (n = 13) confirmed that PDGFR-α expression was strongly linked to metastatic spread (p = 0.0047). PDGFR-α and -β were not found in normal thyroid tissue (p < 0.0001). PTC cell lines selectively expressing PDGFR-α or -β were assessed for invasive potential and activation of downstream signal transduction pathways. PTC cell lines expressing PDGFR-α responded to PDGF-BB stimulation with increased invasive potential and this process can be blocked by the tyrosine kinase receptor inhibitor sunitinib (p < 0.009). Cell lines with only PDGFR-β, or no PDGFR, did not show significant changes in invasive potential. Activation of PDGFR-α led to downstream up-regulation of both the MAPK/ERK and PI3K/Akt pathways and disruption of either pathway is sufficient to block PDGFR-mediated increases in invasive potential. Thus, PDGFR-α is associated with lymph node metastases in papillary thyroid carcinoma and PDGFR-α promotes increased invasive potential in PTC cell lines. PDGFR-α is a strong candidate for a diagnostic biomarker to identify patients at risk of nodal metastases. Our results also strengthen the rationale for selection of tyrosine kinase receptor inhibitors that target PDGFR in the treatment of progressive, metastatic PTC.

Expression profiling of difficult-to-diagnose thyroid histologic subtypes shows distinct expression profiles and identify candidate diagnostic microRNAs

BACKGROUND

The incidence of thyroid cancer is increasing worldwide. The findings of up to 30% of thyroid fine-needle aspiration biopsies (FNAB) are inconclusive, primarily as a result of several thyroid histologic subtypes with overlapping cytologic features. MicroRNAs (miRNAs) are small noncoding RNAs and have been implicated in carcinogenesis. We hypothesized that there are miRNAs that are differentially expressed between benign and malignant thyroid tumors that are difficult to distinguish by FNAB.

METHODS

The expression of 1263 human miRNAs was profiled in 47 tumor samples representing difficult to diagnose histologic subtypes of thyroid neoplasm (21 benign, 26 malignant). Differentially expressed miRNAs were validated by quantitative real-time reverse transcriptase-polymerase chain reaction. The area under the receiver operating characteristic curve (AUC) was used to determine the diagnostic accuracy of differentially expressed miRNAs.

RESULTS

Supervised hierarchical cluster analysis demonstrated grouping of 2 histologies (papillary and follicular thyroid carcinoma). A total of 34 miRNAs were differentially expressed in malignant compared to benign thyroid neoplasms (P<0.05). A total of 25 of the 34 nonproprietary miRNAs were selected for validation, and 15 of the 25 miRNAs were differentially expressed between benign and malignant samples with P-value<0.05. Seven miRNAs had AUC values of >0.7. miR-7 and miR-126 had the highest diagnostic accuracy with AUCs values of 0.81 and 0.77, respectively.

CONCLUSION

To our knowledge, this is the first study to evaluate the diagnostic accuracy of miRNAs in thyroid histologies that are difficult to distinguish as benign or malignant by FNAB. miR-126 and miR-7 had high diagnostic accuracy and could be helpful adjuncts to thyroid FNAB.

The application of molecular diagnostic studies interrogating EGFR and KRAS mutations to stained cytologic smears of lung carcinoma

EGFR and KRAS mutation analyses are of increasing importance for guiding the treatment of non-small cell lung carcinomas. Insufficient cellularity of cell blocks can represent an impediment to the performance of these tests. We investigated the usefulness of cytologic direct smears as an alternative specimen source for mutation testing. Tumor cell-enriched areas from freshly prepared and archived rapid Romanowsky-stained direct smears in 33 cases of lung carcinoma were microdissected for DNA isolation and evaluated for EGFR and KRAS mutations. EGFR mutations were detected in 3 adenocarcinomas; 2 tumors had the L858R substitution and 1 an exon 19 deletion. KRAS mutations affecting codon 12, 13, or 61 were detected in 11 cases (8 adenocarcinomas and 3 non-small cell carcinomas). EGFR and KRAS mutations were mutually exclusive. Hence, archived and freshly prepared direct smears represent a robust and valuable specimen source for molecular studies, especially when cell blocks exhibit insufficient cellularity.

Well-differentiated thyroid carcinomas: management of the central lymph node compartment and emerging biochemical markers

Well-differentiated thyroid cancers (WDTCs) are generally indolent cancers that are associated with a low mortality. Although the incidence of these tumors is increasing, there has not been an associated increase in the mortality rates. As we gain a greater understanding and more experience with these good prognosis cancers, the way in which we treat these tumors is evolving. The definition of persistent or recurrent disease has seen a shift from being a clinical and/or radiological diagnosis to now one based on a biochemical blood marker, thyroglobulin. Central lymph node metastases are a very common problem in WDTC, being present in up to 90% of patients. The optimal surgical management of the central lymph node compartment remains a hotly debated topic. This paper identifies these controversies and presents available data surrounding these issues. Biochemical tumor markers are gaining wider use in practice and in time hopefully provide more specific information with which surgical decision-making can be based. A summary of the clinically available markers is presented.