Microscopic papillary thyroid carcinoma compared with clinical carcinomas by loss of heterozygosity mutational profile

Hürthle cell lesions of the thyroid: Progress made and challenges remaining

Hürthle cell-predominant thyroid fine needle aspirations (FNA) are encountered frequently in routine practice, yet they are often challenging to diagnose accurately and are associated with significant interobserver variability. This is largely due to the ubiquity of Hürthle cells in thyroid pathology, ranging from nonneoplastic conditions to aggressive malignancies. Although limitations in cytomorphologic diagnoses likely will remain for the foreseeable future, our knowledge of the molecular pathogenesis of Hürthle cell neoplasia and application of molecular testing to cytologic material have increased dramatically within the past decade. This review provides context behind the challenges in diagnosis of Hürthle cell lesions and summarizes the more recent advances in diagnostic tools.

Unusual thyroid tumors: a review of pathologic and molecular diagnosis

The most common thyroid neoplasms are either follicular derived (papillary, follicular and Hürthle cell lesions) or C-cell derived (medullary carcinoma). The diagnosis of these tumors can usually be made at the histologic level, with immunohistochemical stains necessary in some circumstances. Specific molecular mutations have been described that can be diagnostically useful or explain, in part, their pathogenesis, including the well-known Ret/PTC and PPARgamma-PAX8 translocations, point mutations in the Ret, Ras and BRAF genes, and loss of heterozygosity of multiple different tumor suppressor genes. Some unusual tumors of the thyroid gland are more difficult to diagnose. In examining these lesions, the pathologist may use the hematoxylin and eosin-stained morphology, coupled with an analysis of the immunohistochemical staining profiles and possibly analysis of the underlying molecular mutational patterns. These less common thyroid tumors include tall cell and cribriform-morular variants of papillary carcinoma, hyalinizing trabecular tumor, mucoepidermoid and sclerosing mucoepidermoid carcinoma with eosinophilia, poorly differentiated (insular) carcinoma, and undifferentiated (anaplastic) carcinoma. The diagnostic features of these rare tumors, including the histology, immunohistochemical expression profiles and the known molecular mutational profiles of each, are reviewed.

Papillary thyroid carcinoma: an update

The past two decades have seen numerous developments in the understanding of the origins and biology of papillary thyroid carcinoma. Advances in molecular biology, clinicopathologic studies of new entities, facility with fine-needle aspiration biopsy, and new radiologic imaging techniques have allowed for earlier diagnosis of these tumors. However, these advances have also caused controversies in cytologic and histopathologic diagnoses as well as therapy decisions. This paper will focus on several pathologic aspects of papillary carcinoma, which impact on its biology and prognosis.

Evaluation of NDRG2 gene expression in primary papillary thyroid carcinoma and in metastases of this neoplasm to regional lymph nodes

Background

At present, researchers' attention has been concentrating on NDRG2 (N-Myc downstream-regulated gene 2) as a new gene candidate in the development and progression of papillary thyroid carcinoma (PTC). NDRG2, together with NDRG1, NDRG3 and NDRG4 are members of the NDRG family, a new class of genes, inhibited by N-Myc oncogene.

Aim

The aim of our study was to evaluate NDRG2 mRNA expression in the primary PTC and its metastases to regional lymph nodes.

Materials and methods

Postoperative tissue and macroscopically changed lymph nodes of sixteen (16) patients with PTC constituted the studied material. In this group, metastases of the cancer to regional lymph nodes were confirmed histopathologically in 8 cases. Quantitative evaluation of NDRG2 mRNA expression was performed by the real-time polymerase chain reaction (real-time PCR) method.

Results

The mean values of NDRG2 mRNA expression in the primary tumour tissues were statistically significantly lower vs. the levels of NDRG2 mRNA expression in macroscopically unchanged thyroid tissue (p < 0.0001). A comparison of the mean NDRG2 mRNA expression of primary tumours and that of their metastases to regional lymph nodes did not demonstrate any statistical differences (p > 0.05). A positive correlation was observed between NDRG2 mRNA expression in primary tumour cells and in the cancer metastases to lymph nodes (Rs = 0.7857; p < 0.05). Factors, such as age, sex, tumour stage in TNM system, were of no significance for NDRG2 mRNA expression level (p > 0.1).

Conclusion

The results of our study demonstrated decreased NDRG2 mRNA expression levels in PTC, when compared to macroscopically unchanged thyroid tissue, which may point to the potential role of NDRG2 in the development and progression of cancer in question.

Value of specimen radiographs in diagnosing multifocality of thyroid cancer

BACKGROUND

Specimen radiography has been used widely to evaluate the complete excision of calcified breast lesions but has not been evaluated for thyroid cancer.

METHODS

Specimen radiographs were evaluated retrospectively to identify additional cancers that were demonstrated only as calcifications. Receiver operating characteristic curve analysis was performed to compare the combination of specimen radiography and ultrasonography versus ultrasonography alone for detecting multifocality.

RESULTS

Some 122 thyroid cancer specimens were obtained from 122 patients between January and April 2008. Specimen radiography detected 27 cancers (18.5 per cent) not detected by ultrasonography. Diagnoses were changed after evaluation of specimen radiographs in three of these patients. The area under the curve of the combination of specimen radiography and ultrasonography was significantly higher than that of ultrasonography alone (P = 0.005).

CONCLUSION

Specimen radiography is a potentially useful tool for diagnosing cancer type and predicting the extent of thyroid cancer.

The cytoplasmic expression of MUC1 in papillary thyroid carcinoma of different histological variants and its correlation with cyclin D1 overexpression

This study addressed the immunohistochemical expression of MUC1 in papillary thyroid carcinoma (PTC) of different histotypes, sizes, and morphological features of aggressiveness, and its correlation with the overexpression of cyclin D1, a target molecule of the Wnt pathway. MUC1 expression was examined in a total of 209 PTCs. Cytoplasmic MUC1 expression was elevated in the tall, columnar cell and oncocytic variants (100%), Warthin-like (78%), and conventional PTCs (61%), and in papillary microcarcinoma (PMC) with the conventional growth pattern (52%). On the contrary, it was low in the follicular variant (27%) of PTC and PMCs with follicular architecture (13%). Cytoplasmic MUC1 accumulation did not associate with any clinicopathological features except peritumoral lymphoid infiltration in PTCs and in PMCs with the conventional growth pattern. MUC1 staining correlated with cyclin D1 overexpression in conventional PTCs and PMCs and PMCs with follicular architecture. The results demonstrate that MUC1 expression varies broadly in different histological variants of PTC, being the lowest in tumors with follicular structure. In general, it does not prove to be a prognosticator of PTC aggressiveness. A high correlation between MUC1 and cyclin D1 implies MUC1 involvement in the Wnt cascade functioning in a large subset of human PTCs and PMCs.

Microcarcinoma of the thyroid

Thyroid microcarcinoma, defined as a thyroid tumor measuring 1 cm or less, is an extremely indolent tumor. Papillary microcarcinoma, the most common subtype, is often identified incidentally in a thyroid removed for benign clinical nodules or diffuse processes (eg, thyroiditis). In this clinical situation, over 99% are cured by simple lobectomy. In the less common scenario, the microcarcinoma is the primary lesion to a lymph node metastasis presenting clinically as a neck mass; in this situation, the tumor should be treated as a clinical cancer. Other rare microcarcinomas can occur and, of these, the most recently described is micromedullary carcinoma. In the familial setting, these lesions are identified in prophylactic thyroidectomies and are not unexpected findings. However, when found as sporadic tumors, their implications are still unknown. The histologic features, pathologic mimics, and molecular facets of these microscopic neoplasms are discussed in this review.

The BRAF mutation is not associated with poor prognostic factors in Korean patients with conventional papillary thyroid microcarcinoma

BACKGROUND

The BRAF(V600E) mutation, the most common genetic alteration reported in papillary thyroid carcinoma, has been associated with poor prognostic factors.

AIM

To determine whether the presence of the BRAF(V600E) mutation is associated with poor prognosis in Korean patients with conventional papillary thyroid microcarcinoma (micro-PTC).

PATIENTS AND METHODS

DNA was extracted from paraffin-embedded thyroid tumour specimens taken from 60 patients with conventional micro-PTC, as well as from nine patients with follicular variant papillary carcinoma, six with nodular hyperplasia, four with follicular carcinoma (including one with Hürthle cell carcinoma), four with follicular adenoma (including two with Hürthle cell adenoma) and one each with medullary carcinoma, poorly differentiated carcinoma and anaplastic carcinoma. The presence of the BRAF(V600E) mutation was determined by polymerase chain reaction (PCR) amplification of exon 15 followed by direct sequencing.

RESULTS

The BRAF(V600E) mutation was detected in tumour samples from 31 of 60 conventional micro-PTC patients (52%), but was not detected in patients with other types of thyroid tumours. The age distribution, tumour size, extrathyroid extension, multifocality and staging did not differ significantly between patients with and without the BRAF(V600E) mutation.

CONCLUSION

In Korean patients with conventional micro-PTC, the presence of the BRAF(V600E) mutation was not significantly associated with prognostic factors.

Cyclin D1 overexpression in thyroid papillary microcarcinoma: its association with tumour size and aberrant beta-catenin expression

AIMS

Cyclin D1 is a target molecule transcriptionally activated by aberrant beta-catenin in Wnt signalling. Thyroid papillary microcarcinoma (PMC) may be considered a precursor of papillary thyroid cancer (PTC). Ki67 is widely used as a proliferation marker. The aim of this study was to determine whether cyclin D1 overexpression is involved in early thyroid carcinogenesis.

METHODS AND RESULTS

Thirty-five cases of PMC were examined immunohistochemically, including 11 cases less than 5 mm (PMC < 5) and 24 cases more than 5 mm (PMC > 5), and 18 PTC cases (size 11-15 mm). Cyclin D1 expression was significantly lower in PMC < 5 than in PMC > 5, while there was no significant difference between PMC > 5 and PTC. Statistical analysis revealed significant correlations between cyclin D1 labelling index (LI) and Ki67 LI (P = 0.0272)/cytoplasmic beta-catenin expression (P < 0.001) in PMC and PTC. Four of five PMC > 5 cases with lymph node (LN) metastases displayed a high cyclin D1 LI and strong cytoplasmic beta-catenin expression.

CONCLUSIONS

Cyclin D1 overexpression and correlation with aberrant beta-catenin expression were demonstrated in PMC. Cyclin D1 expression was significantly associated with tumour size and LN metastases in PMC. Cyclin D1 may be up-regulated at an early stage of thyroid carcinogenesis and promote tumour growth and metastatic potency in PMC through activation of the Wnt/beta-catenin pathway.

Papillary carcinoma of the thyroid ≤ 1.0 cm

BACKGROUND

Papillary carcinomas of the thyroid that measure <or=1.0 cm often are termed incidental or occult tumors. In the current study, the author sought to determine the incidence of such tumors at his institution over a relatively short period.

METHODS

The author reviewed the results from all patients who underwent thyroid resection over a 65-month period and correlated the findings with clinical and cytologic information.

RESULTS

During the study period, a total of 720 resections were performed, and 210 papillary carcinomas were identified that were the reason for the excision. The mean size of these tumors decreased from 2.1 cm to 1.7 cm (P=0.018) over the period of the study, and the percentage of tumors measuring <or=1.0 cm increased from 21% to 39% (P=0.007). The vast majority of these small tumors (73%) were identified by preoperative fine-needle aspiration. During the same period, there were 62 incidental papillary carcinomas, 94% of which measured <or=0.5 cm.

CONCLUSIONS

The size of papillary thyroid carcinomas that were resected at the author's institution decreased significantly, and carcinomas measuring <or=1.0 cm increased significantly. Currently, papillary carcinomas that measure between 0.5 cm and 1.0 cm rarely are either occult or incidental findings in the majority of patients.

Molecular profiling of primary and metastatic neoplasms in the lung using cytologic material obtained by fine-needle aspiration: report of two cases

Two cases are presented in which molecular analyses of cytologic material obtained by fine-needle aspiration were helpful in establishing relationships between morphologically similar neoplasms in the same patient. For appropriate clinical management, it is important to ascertain whether the tumors represent independent primaries or metastases. Alcohol-fixed cytologic material prepared as cell blocks and formalin-fixed paraffin-embedded tissue were microdissected and analyzed for allelic loss of heterozygosity at multiple preselected genetic loci. The first case illustrates a 69-yr-old man with multiple intrapulmonary nodules involving the upper and lower lobes of the left lung. Genomic analysis showed that the neoplasms in the left upper and lower lung lobes were independent primaries, because the loss of heterozygosity (LOH) patterns were substantially different. By contrast, the second case is that of a 58-yr-old man with a right thyroid nodule and multiple pulmonary tumors. LOH analysis confirmed that a sampled pulmonary tumor represented a metastasis from the thyroid primary, as similar LOH patterns involving locus D9S252 were observed on comparison of the thyroid and pulmonary neoplasms. These cases illustrate the practical diagnostic utility of genomic analysis using cytologic material in the assessment of primary and metastatic malignancies.

Tumor suppressor gene allelic loss profiles of the variants of papillary thyroid carcinoma

Papillary thyroid carcinoma (PTCa) is a relatively common, indolent tumor that usually has an excellent prognosis. While the diagnosis of conventional PTCa is relatively straightforward, encapsulated tumors with follicular growth pattern and unusual or incomplete cytologic features of papillary carcinoma can be diagnostically challenging. Encapsulated, noninvasive tumors are particularly controversial as the differential diagnosis includes a nonneoplastic nodule, a benign follicular adenoma, and papillary carcinoma. In this study, we performed molecular genotyping to identify loss of heterozygosity of tumor suppressor genes in conventional PTCa and in several different morphologic variants, including follicular variant, tall cell variant, and oncocytic variant. Our data demonstrate that conventional PTCas have the lowest frequency of allelic loss (7%), as compared with follicular, oncocytic, and tall cell variants (19%, 34%, and 20%, respectively). Frequency of allelic loss increased with increasing size of the tumors, but did not correlate with age, gender, extrathyroidal extension, or lymph node metastases. Though it is unlikely that these results will enable the distinction between different variants of papillary carcinoma, the finding of significant rates ofallelic loss in the variants of PTCa provides additional evidence of malignancy and may be useful in distinguishing encapsulated tumors from nonneoplastic or benign nodules.

Molecular genotyping of medullary thyroid carcinoma can predict tumor recurrence

Medullary thyroid carcinoma can have an aggressive behavior, and little is known about the molecular basis for clinical outcome. Defining risk of recurrent or metastatic disease is difficult, and it has been limited to clinical and pathologic features, such as advanced age, cervical lymph node metastases, and stage at presentation. Using microdissection and genotyping, we studied 11 cases of medullary carcinoma for allelic losses in a panel of known tumor suppressor genes. The tumor suppressor genes with the most frequent allelic losses were NF2, l-myc, and p53 (75%, 44%, and 44%, respectively). The average frequency of allelic loss across all tumors was 44% and was higher in tumors that recurred. A combination of previously described high-risk variables (increased patient age and cervical lymph node metastases) with the frequency of allelic loss yielded a high-risk group, in which 6 of 6 patients recurred, and a low-risk group, in which 0 of 5 patients recurred (P = 0.004). Frequency of allelic loss in tumor suppressor genes may provide a useful adjunctive prognostic test in medullary thyroid carcinoma.

Molecular evidence of anaplastic transformation in coexisting well-differentiated and anaplastic carcinomas of the thyroid

Anaplastic thyroid cancer is a rare but nearly universally fatal tumor. Epidemiologic data suggest that many anaplastic thyroid carcinomas arise from transformation of preexisting or coexisting well-differentiated thyroid carcinomas. At the molecular level, the mutations responsible for the anaplastic transformation are incompletely understood, although the mutational events are thought to involve tumor suppressor genes. To examine transformation from a well-differentiated thyroid carcinoma to anaplastic carcinoma, we studied coexisting well-differentiated (Hürthle cell and papillary carcinoma) and anaplastic tumors with a molecular genotyping panel of tumor suppressor genes associated with thyroid neoplasia. The patterns of allelic loss in our results showed that the majority of cases have a core of conserved mutations in the two morphologically distinct areas and substantial increases in mutation rates in the anaplastic components.

Loss of heterozygosity of the VHL gene identifies malignancy and predicts death in follicular thyroid tumors

BACKGROUND

Follicular thyroid tumors (FTT) usually require resection to distinguish adenoma from carcinoma. Better markers that predict histologic subtype and prognosis are needed for FTT.

METHODS

Seventeen benign and malignant FTT with follow-up were selected. Pathologic diagnosis was confirmed, tumor and normal tissue were microdissected, and DNA was extracted. Polymerase chain reaction (PCR) products for a microsatellite marker at the von Hippel Lindau gene (VHL) gene locus (3p26) were analyzed with semiquantitative capillary gel electrophoresis to detect loss of heterozygosity (LOH). Data were assessed for statistical significance with chi(2).

RESULTS

Mean follow-up was 77 months (range 29 to 120 months). Four cases were uninformative (homozygous microsatellite). Among 13 evaluable patients (6 adenomas, 7 follicular cancers) LOH of VHL was present only in carcinomas (P=.013). LOH was present in 4/4 patients with recurrence and 0/3 patients without recurrence (P=.017). Death from disease has occurred in 3 patients. LOH of VHL was strongly associated with death from disease (P=.034).

CONCLUSIONS

FTT can be analyzed for LOH at the VHL gene locus. In this initial study, LOH of VHL was highly specific for malignancy and predicted death from disease. The analysis of VHL may provide for preoperative detection in cytologic samples with potential impact on clinical management of FTT.

Controversies in papillary microcarcinoma of the thyroid

Papillary thyroid carcinomas that are smaller than 1 cm are classified as papillary microcarcinomas (PMC). These lesions are frequently detected as incidental findings on autopsy or in surgical specimens. They are often multifocal. The relationship between PMC and clinical papillary thyroid carcinoma (PTC) is not clear. In patients with clinical thyroid cancer, PMC may represent intrathyroidal metastases; they may be the earliest form of future large lesions. These uncertainties raise questions about appropriate clinical management of patients with these lesions. Review of the literature substantiates the argument that clinically evident PTC may be distinctly different from solitary or multifocal PMC in terms of etiology and biologic behavior, supporting a conservative approach to management.