Thyroid peroxidase immunodetection as a tool to assist diagnosis of thyroid nodules on fine-needle aspiration biopsy

Morphometric study in thyroid tumors

Various morphonuclear studies using digital image analysis have been taken into account in order to establish the malignancy of thyroid lesions based on their size and on the chromatographic characteristics of tumor cell nuclei. Nuclear morphometry involves the measurement of nuclear parameters to obtain diagnostically important information in an objective and reproducible manner. The aim of the present study was to evaluate the detailed morphometric analysis of histopathological preparations with lesions of the thyroid gland and to investigate its role in differentiating between benign and malignant thyroid lesions. The present study included 10 benign and 26 malignant thyroid cases with different selected thyroid lesions. Using a microscope connected to a computerized video system, nuclear morphometric parameters including the nuclear area, perimeter, average intensity, red average, width and roundness, were measured and analyzed. The main parameters used in the statistical calculation were significant in distinguishing between benign and malignant thyroid lesions. The association of morphometry in cytological smears for suspected malignant follicular lesions led to increased accuracy in establishing a suspicious malignant diagnosis for follicular lesions. Nuclear morphometry provides an unbiased point of view that increases diagnosis accuracy. Computerized morphometry can positively influence diagnostic accuracy, allowing for a better correlation with clinical and imaging data.

Effect of recombinant human thyroid stimulating hormone on long-term salivary gland dysfunction in thyroid cancer patients treated with radioactive iodine. A systematic review

Adjuvant radioactive iodine (RAI) is administered to thyroid cancer patients following thyroidectomy for remnant tissue ablation and metastatic disease management. Patients are prepared with thyroid hormone withdrawal (THW) or recombinant human thyroid stimulating hormone (rhTSH). Long-term salivary gland dysfunction (LT-SGD) is a common, dosage-dependent, RAI adverse effect. Although rhTSH preparation seems to reduce LT-SGD, this effect could be due to lower RAI activity generally used in rhTSH-prepared patients. Therefore, this meta-analysis investigated the effect of preparation type on LT-SGD development. Literature search (PubMed, Medline, EmBase, Cochrane, Web of Science, LILACS, Google Scholar) was performed four times (January-November 2022) and studies reporting LT-SGD incidence ≥1 year after RAI in patients prepared with rhTSH/THW were identified. The LT-SGD risk ratio (RR) was estimated with various models considered for sensitivity analysis (fixed-effect, random-effects, study-quality adjusted, publication-bias adjusted, individual-patient-data meta-analysis adjusted for RAI). Subgroup analysis according to RAI activity (<3.7/≥3.7 GBq) also was performed. Literature search resulted in five studies (321 rhTSH, 632 THW patients). The pooled RRs according to various models were 0.65 (95% confidence interval -95CI, 0.49-0.86; fixed-effect); 0.62 (95CI, 0.38-1.02; random-effects); 0.72 (95CI, 0.54-0.96; quality adjusted); 0.76 (95CI, 0.58-0.99; publication-bias adjusted); 0.0.80 (95CI, 0.55-1.14; individual-patient-data meta-analysis). The pooled RRs stratified for RAI activity were 0.26 (95CI, 0.05-1.30) for <3.7 GBq; 0.75 (95CI, 0.57-0.98) for ≥3.7 GBq. The number of patients needed to be prepared with rhTSH to prevent one case of LT-SGD ranged between seven and thirty-seven. There is moderate-quality scientific evidence that rhTSH preparation may consistently protect salivary gland function.

Cytomorphological Spectrum of Thyroiditis: A Review of 110 Cases

Introduction

Different types of thyroiditis may share some parallel clinical and biochemical features. Timely intervention can significantly reduce morbidity and mortality.

Aim

Aim of this study is to find the frequency of various thyroiditis, study the cytomorphological features and correlate with clinical findings including radiological findings, thyroid function test, and anti-thyroid peroxidase antibodies (Anti-TPO antibodies).

Materials and Methods

The study included consecutive 110 cases of thyroiditis. Detailed cytomorphological features were studied and correlated with ultrasonography findings, thyroid function test, anti-thyroid peroxidase antibodies (anti-TPO) and histopathological features where thyroidectomy specimens were received for histopathological examination.

Results

The majority were Hashimoto's thyroiditis (n = 100) and females (n = 103). Other forms of thyroiditis were Hashimoto's thyroiditis with colloid goiter (n = 5), De Quervain's thyroiditis (n = 3), and one case each of postpartum thyroiditis and Hashimoto's thyroiditis with associated malignancy. The majority of patients were in the age group of 21-40 (n = 70) and the majority (n = 73) had diffuse enlargement of thyroid. The majority of patients were hypothyroid (n = 52). The serum anti-TPO antibodies were elevated in 47 patients out of 71 patients. In the 48 patients who underwent ultrasonography, 38 were diagnosed as having thyroiditis. The most consistent cytomorphological features seen in fine-needle aspiration smears of Hashimoto's thyroiditis were increased background lymphocytes, lymphocytic infiltration of thyroid follicular cell clusters, and Hurthle cells.

Conclusion

The diagnostic cytological features in Hashimoto's thyroiditis are increased background lymphocytes, lymphocytic infiltration of thyroid follicular cell clusters, and Hurthle cells. FNAC remains the "Gold Standard" for diagnosing Hashimoto's thyroiditis. Clinical history, thyroid function, and biochemical parameters are the key for diagnosis of other forms of thyroiditis.

A study of malignancy rates in different diagnostic categories of the Bethesda system for reporting thyroid cytopathology: An institutional experience

Background

The Bethesda system for reporting thyroid cytopathology (TBSRTC) was introduced to standardize the communication of fine-needle aspiration cytology (FNAC) interpretation between clinicians and pathologists. This study was undertaken to evaluate the diagnostic utility of TBSRTC for reporting thyroid FNACs and rate of malignancy in each diagnostic category of TBSRTC.

Methods

A total of 603 thyroid FNAC results were retrieved retrospectively between July 2012 and January 2015 and reclassified according to TBSRTC. Of these, 392 cases had a histopathological follow-up. The FNACs results were compared to the histopathological diagnoses and the malignancy rates of each diagnostic categories of TBSRTC were calculated.

Results

Of the 603 FNACs, nondiagnostic were 16 (2.7%), benign were 393 (65.2%), atypia of undetermined significance/follicular lesion of undetermined significance (AUS/FLUS) were 60 (10%), follicular neoplasm/suspicious for a follicular neoplasm (FN/SFN) were 64 (10.6%), suspicious for malignancy (SM) were 32 (5.3%), and malignant were 38 (6.3%). In 392 cases, there was follow-up histopathology. The malignancy rate for nondiagnostic, benign, AUS/FLUS, FN/SFN, SM, and malignant categories were 0%, 0.8%, 24.4%, 28.9%, 70.8%, and 100%, respectively.

Conclusion

Our study validated the efficacy of TBSRTC. In conclusion, the malignancy rate of AUS/FLUS in this study was higher than the risk mentioned in TBSRTC and other published studies. Hence, AUS/FLUS category patients in our setup warrant further workup including ultrasound and/or thyroid scan in addition to immediate repeat FNAC.

Importance of Hormones and Proteins Determination in the Material Obtained by Fine-Needle Aspiration

More than a half century of experience with aspiration punch of nodal changes in the thyroid gland has confirmed this procedure as a golden standard in the examination of thyroid nodal disease. Although sensitivity, specificity, reliability and reproducibility are incontestably high, this procedure cannot give a simple answer on whether the change examined is benign or malignant. Numerous attempts to improve the procedure resulted in considerably advanced findings. Besides refining the cytopathologic examination techniques, confirmation or determination of hormones, proteins and other substances in the material obtained by fine-needle aspiration are actually the greatest contribution to improvement the of procedure's diagnostic value. These markers are actually followed, in most medical centers, in aspirates of thyroid nodal changes but also surrounding lymph nodes in order to evaluate with greater certainty the type, volume and spread; this is important to establish treatment procedures and to evaluate the residual disease after accomplishing the treatment.

Application of immunohistochemistry to thyroid neoplasms

CONTEXT

Thyroid lesions with nodular architecture and follicular pattern of growth often pose difficulties in accurate diagnosis during the assessment of cytologic and histologic specimens. The diagnosis of follicular neoplasm on cytology or of follicular tumor of uncertain malignant potential on histology is likely to cause confusion among clinicians and delay effective management of these lesions. Occasionally, thyroid tumors represent unusual or metastatic lesions and their accurate diagnosis requires immunohistochemical confirmation.

OBJECTIVE

To review the literature on the applications of immunohistochemistry in the differential diagnosis of thyroid tumors.

DATA SOURCES

Relevant articles indexed in PubMed (National Library of Medicine) between 1976 and 2006.

CONCLUSIONS

Our review supports the use of ancillary techniques involving a panel of antibodies suitable for immunohistochemistry and molecular analysis in the assessment of thyroid nodules. These tools can improve diagnostic accuracy when combined with standard morphologic criteria.

Utility of malignancy markers in fine-needle aspiration cytology of thyroid nodules: comparison of Hector Battifora mesothelial antigen-1, thyroid peroxidase and dipeptidyl aminopeptidase IV

The purpose of this study was to compare the diagnostic interest of Hector Battifora mesothelial antigen-1 (HBME-1), thyroid peroxidase (TPO), and dipeptidyl aminopeptidase IV (DPP4) in thyroid fine-needle aspirates obtained from 200 resected thyroid lesions (55 colloid nodules, 54 follicular adenomas, 59 papillary cancers, and 32 follicular carcinomas). Hector Battifora mesothelial antigen-1 or TPO expression (% positive cells) and DPP4 staining score (12-point scale) were evaluated. Receiver operating characteristic (ROC) curves were plotted and optimal cutoff values for diagnosing malignancy were determined. The TPO ROC curve was consistently higher than the HBME-1 ROC curve. The TPO curve was also higher than the DPP4 curve with regard to sensitivity, but dipped below the DPP4 curve with regard to specificity. Using a cutoff value of <80% positive cells for TPO, >10% positive cells for HBME-1, and staining score > or =1 for DPP4, sensitivity to specificity ratios were 98-83% for TPO, 90-60% for HBME-1, and 88-80% for DPP4. Two particularly interesting findings of this study were the low negative likelihood ratio of TPO (0.02) allowing highly reliable exclusion of malignancy and the 100% specificity of DPP4 staining scores=12. Due to poor performance on follicular lesions, HBME-1 showed no advantage over TPO or DPP4.

Poorly differentiated follicular thyroid carcinoma: prognostic factors and relevance of histological classification

OBJECTIVE

Poorly differentiated follicular thyroid carcinoma (PDFC) is a tumor of follicular cell origin with attributes intermediate between well-differentiated carcinomas and anaplastic carcinomas, but neither a clear histological description nor an established definition of prognostic indicators are available.

DESIGN

This study correlates the clinical outcome and survival of 40 PDFC patients with histological architecture, cytological characteristics, and expression of various markers of cell proliferation and differentiation (cyclin A, cyclin B1, cyclin D1, cyclin E, Ki67, thyroperoxidase, galectin 3, dual oxidase [Duox], vascular endothelial growth factor, epidermal growth factor receptor, and p53).

MAIN OUTCOME

At 5 years, the overall survival rate was 63% and the metastasis-free survival rate was 57%. An older age at the time of diagnosis and a larger tumor size were associated with an increased risk of distant metastases and of cancer-related death. Polymorph architecture was associated with a reduced risk of metastases, whereas a high expression of Duox was associated with a reduced risk of death. In these patients with PDFC, no other histological features or expression of any other marker had a prognostic significance.

CONCLUSION

PDFC has a more aggressive behavior than well-differentiated carcinomas; prognosis is related to indicators that are also relevant in patients with well-differentiated carcinomas.

Diagnostic molecular markers in thyroid cancer

The use of molecular assays to analyze clinical tissues in the diagnosis and management of thyroid cancer, similar to other tumors, will likely allow for more accurate characterization of the aggressiveness of individual tumors and may allow for the early diagnosis of recurrence. The application of these methods to thyroid nodules and nodal metastases is less encumbered by difficulties arising from amplification of transcripts in non-thyroid cells. For these tissues, these assays are likely to be used clinically in the near-future. New data arising from cDNA arrays identifying novel markers of malignancy or tumor aggressiveness make this a growing area of interest. The use of molecular assays in diagnosing distant metastases is more problematic due to issues with ectopic expression of either full length or splice variants of genes thought to be thyroid-specific. Assay quantitation is a complex problem owing to variability in the level of expression of "housekeeping" genes and the variety of phlebotomy and RT-PCR methods reported. Additional research in this area is clearly required before a recommendation can be given regarding clinically applicability of these tests.

Monoclonal antibodies to thyroid specific autoantigens

Monoclonal antibody (MAbs) is a powerful and essential tool to perform studies concerning antigens and antibodies at molecular level. MAbs to major thyroid specific autoantigens, thyroglobulin (Tg), thyroid peroxidase (TPO) and TSH receptor (TSHR), have been prepared and applied for a variety of investigations including the structure of antigens and antibodies, the expression of antigens, the epitopes of antibodies, the functional regions of antigens, mutated antigens in congenital diseases, and clinical applications to diagnosis of various thyroid diseases. Recently, sodium iodide symporter (NIS) was identified and became a potential thyroid autoantigen related to autoimmune thyroid disease, although few MAbs to NIS have been prepared. In this manuscript, I primarily focus on studies concerning MAbs to three major thyroid specific autoantigens, Tg, TPO and TSHR, and summarize studies using the mAbs.

Galectin-3: presurgical marker of thyroid follicular epithelial cell-derived carcinomas

Preoperative follicular lesion characterisation represents an unsolved diagnostic problem in thyroid nodular disease. Although fine-needle aspiration biopsy is the most reliable preoperative diagnostic procedure, it shows inherent limitations in differentiating adenoma from follicular carcinoma and, sometimes, follicular variants of papillary carcinoma. Galectin-3 cytoplasmic neoexpression has been proposed as a peculiar feature of thyroid malignant cells, easily detectable in cytological and histological samples. The aim of this study was to re-evaluate the galectin-3 expression in a large sample of thyroid lesions using an immunohistocytochemical biotin-free detection system and a specific anti-human-galectin-3 monoclonal antibody in order to avoid the interference of technical factors, a cause of conflicting results recently reported by some authors. We analysed galectin-3 expression of 39 follicular carcinomas, 26 papillary carcinomas, and 105 adenomas in both cell-block samples and their histological counterparts. All cell-block and histological papillary carcinoma samples showed high levels of galectin-3 immunoreactivity. Thirty-four follicular carcinomas were positive, whereas 5 were negative in cell-blocks but positive in their histological counterparts. Twelve out of 105 adenomas expressed galectin-3 in cell-blocks and histological samples. The diagnostic accuracy of preoperative galectin-3 evaluation in adenomas vs follicular carcinomas was 90.0%. Galectin-3 expression was also investigated in 22 minimally-invasive follicular carcinomas. All of them showed galectin-3 immunoreactivity in both cytological and histological specimens with the exception of two cases, where galectin-3 positivity was observed only in the surgical material. The routine correct use of galectin-3, by increasing the diagnostic accuracy of conventional cytology, improves the management of thyroid nodules and can lead to a sensitive reduction of useless thyroid surgeries.

Molecular pathogenesis of thyroid cancer

A number of molecular abnormalities have been described in association with the progression from normal thyroid tissue to benign adenomas to well-differentiated and finally anaplastic epithelial thyroid cancer. These include upregulation of proliferative factors, such as growth hormones and oncogenes, downregulation of apoptotic and cell-cycle inhibitory factors, such as tumor suppressors, disruption of normal cell-to-cell interactions, and cellular immortalization. The progression model for thyroid carcinoma has not been proven, but evidence suggests that an evolutionary molecular process is involved, especially in the development of follicular thyroid cancers for which there are distinct intermediate phenotypes. We present a comprehensive evaluation of factors involved in thyroid tumorigenesis and attempt to describe preliminary attributes of a progression model. The organization of this model should also provide a template for the incorporation of new information as it is derived from large-scale genomic studies.

Management of simple nodular goiter: current status and future perspectives

The simple nodular goiter, the etiology of which is multifactorial, encompasses the spectrum from the incidental asymptomatic small solitary nodule to the large intrathoracic goiter, causing pressure symptoms as well as cosmetic complaints. Its management is still the cause of considerable controversy. The mainstay in the diagnostic evaluation is related to functional and morphological characterization with serum TSH and (some kind of) imaging. Because malignancy is just as common in patients with a multinodular goiter as patients with a solitary nodule, we support the increasing use of fine-needle aspiration biopsy (cytology). Most patients need no treatment after malignancy is ruled out. In case of cosmetic or pressure symptoms, the choice in multinodular goiter stands between surgery, which is still the first choice, and radioiodine if uptake is adequate. In addition to surgery, the solitary nodule, whether hot or cold, can be treated with percutaneous ethanol injection therapy. If hot, radioiodine is the therapy of choice. Randomized studies are scarce, and the side effects of nonsurgical therapy are coming into focus. Therefore, the use of the optimum option in the individual patient cannot at present be based on evidence. However, we are of the view that levothyroxine, although widely used, should no longer be recommended routinely for this condition. Within a few years, the introduction of recombinant human TSH and laser therapy may profoundly alter the nonsurgical treatment of simple nodular goiter.

Influence of iodine intake on the diagnostic power of fine-needle aspiration cytology of the thyroid gland

In order to determine whether the iodine intake influences the diagnostic power of ultrasound-guided fine-needle aspiration cytology (US-FNAC), patients with nontoxic nodular goiter from an area with sufficient iodine intake (IS) (n = 938, median iodine excretion [MIE] = 103 microg/L) and from an iodine-deficient (ID) area (n = 3,601, MIE = 75 microg/L) were investigated. Elevated rates of multinodularity (59.6% vs. 49.6%, p < 0.001), nonpalpable nodules (47.6% vs. 37.3%, p < 0.001) and nondiagnostic US-FNACs (8.8% vs. 5.1%, p = 0.008), and a lower malignancy rate (1.2% vs. 2.3%, p = 0.006) were found in the ID area. Follicular tumors were encountered among positive findings. Cytohistologic comparison (ID, n = 416; IS, n = 97) revealed that the sensitivity, specificity, and diagnostic accuracy of US-FNAC were similar in the two areas (95.5% vs. 92.3%, 78.3% vs. 71.1%, 82.4% vs. 80.6%, IS vs. ID area, respectively), while a lower malignancy rate and a higher ratio of benign to malignant tumors were observed in the ID than in the IS area (10.1% vs. 22.6%, p < 0.001, and 4.38 vs. 1.50, p < 0.001, respectively). This resulted in a lower positive predictive value of US-FNAC in the ID (36/106) than in the IS area (21/36, p = 0.001), because the rate of false US-FNAC was higher in benign (67/184) than in malignant tumors (4/61, p < 0.001).

Is there loss or qualitative changes in the expression of thyroid peroxidase protein in thyroid epithelial cancer?

There is disagreement concerning the expression of thyroid peroxidase (TPO) in thyroid cancer, some studies finding qualitative as well as quantitative differences compared to normal tissue. To investigate TPO protein expression and its antigenic properties, TPO was captured from a solubilizate of thyroid microsomes by a panel of murine anti-TPO monoclonal antibodies and detected with a panel of anti-human TPO IgGkappa Fab. TPO protein expression in 30 samples of malignant thyroid tissue was compared with TPO from adjacent normal tissues. Virtual absence of TPO expression was observed in 8 cases. In the remaining 22 malignant thyroid tumours the TPO protein level varied considerably from normal to nearly absent when compared to normal thyroid tissue or tissues from patients with Graves' disease (range less than 0.5 to more than 12.5 microg mg(-1) of protein). When expressed TPO displayed similar epitopes, to that of TPO from Graves' disease tissue. The results obtained by the TPO capturing method were confirmed by SDS-PAGE and Western blot analysis with both microsomes and their solubilizates. The present results show that in about two-thirds of differentiated thyroid carcinomas, TPO protein is expressed, albeit to a more variable extent than normal; when present, TPO in malignant tissues is immunologically normal.

[Immunodetection of thyroid peroxidase in the diagnosis of follicular variants of thyroid papillary cancer]

STUDY AIM

The aim of this retrospective study was to assess the role of thyroid peroxidase immunodetection in the cytological diagnosis of follicular variants of thyroid papillary cancer (FVTPC) which are difficult to identify by standard cytology.

PATIENTS AND METHODS

Between 1991 and 1998, 3,505 thyroid fine needle aspiration biopsies were performed by thyroid peroxidase immunocytochemistry and 1,576 patients were operated on. Out of a total of 227 thyroid papillary cancers (TPC), 42 (18.5%) were diagnosed as FVTPC. The results of standard cytology and thyroid peroxidase immunodetection were compared with the histological findings.

RESULTS

The rate of false negatives for TPC in standard cytology was 11% (25/227 cases), with 40% of these false negatives being FVTPC; ten out of 42 (23.8%) cases of FVTPC were not identified by standard cytology. However, cytology with thyroid peroxidase immunodetection diagnosed 224 out of the 227 TPC (99%), and all the FVTPC were correctly identified (100%).

CONCLUSION

FVTCP are the most frequent source of false negatives in standard cytology. Thyroid peroxidase immunodetection allows most of these errors to be avoided, and correctly identifies 99% of TPC including FVTPC.

Molecular diagnostic tests in the diagnosis and management of thyroid carcinoma

The application of molecular analysis of gene expression to clinical tissue samples represents one of the most exciting new areas in "translational" thyroid cancer research. Current data suggest that molecular diagnostic assays may improve the sensitivity and accuracy of fine needle aspiration of thyroid nodules, fine needle aspiration of metastases, and detection of recurrent disease in peripheral blood samples. It is likely that at least some of these tests will become useful adjuncts in the diagnostic armamentarium of clinical endocrinologists in the future.

In situ hybridization and immunohistochemistry study of thyroid peroxidase expression in thyroid tumors

Malignant thyroid tumors reportedly exhibit an anomaly in thyroid peroxidase (TPO) resulting in a lower affinity for monoclonal antibody 47 (mAb 47) in immunohistochemistry studies. The purpose of the present study was to compare TPO immunostaining in normal, benign, and malignant thyroid tissue with expression of mRNA sequences in four exons of the molecule including the epitope of mAb 47. TPO immunostaining was performed using mAb 47 and a polyclonal antibody (pAb). Messenger RNA expression was investigated by in situ hybridization using probes specific for mRNA sequences in exons 2, 12 (epitope of mAb), 15, and 17. As expected, pAb immunostaining was significantly positive on all benign tumors and 50% of carcinomas. With mAb 47, little or no immunostaining was observed in 16 of 17 carcinomas while significantly positive immunostaining was found in normal tissue and benign tumors. In situ hybridization showed a decrease and heterogeneity in the expression of all mRNA sequences in carcinomas as compared to normal tissue and benign tumors. Unlike the other three probes, the probe specific for exon 12 hybridized strongly with benign tumors but poorly with most carcinomas. Poor hybridization was usually correlated with defective mAb 47 immunostaining. These results confirm that TPO is expressed in thyroid carcinomas but in smaller amounts than in normal tissue and benign tumors. In malignant tumors, qualitative changes in TPO may also impede mAb 47 immunostaining. In situ hybridization showed a concomitant decrease in the corresponding TPO mRNA sequence. These changes could be due to abnormalities in the maturation of TPO mRNA leading to a different splicing variant.

The value of thyroid peroxidase immunohistochemistry for preoperative fine-needle aspiration diagnosis of the follicular variant of papillary thyroid cancer

BACKGROUND

With the use of May-Grunwald-Giemsa staining, cytologic features of the follicular variant of papillary thyroid cancers (FVPTCs) on thyroid fine-needle aspiration (FNA) often resemble those of hyperplastic and adenomatous nodules. Detection of reduced staining after thyroid peroxidase (TPO) immunohistochemistry with monoclonal antibody MoAb47 has been shown to be a helpful diagnostic marker. The purpose of this study was to assess the value of TPO immunohistochemistry for the diagnosis of FVPTC.

METHODS

Of 3505 patients with adequate FNA samples, 1576 patients underwent surgical procedures. Histologic examination of the surgical specimen demonstrated papillary thyroid cancer in 227 cases, including 42 FVPTCs (18%). The diagnostic accuracy of standard thyroid FNA and TPO immunohistochemistry, which we use routinely, was compared in these 42 FVPTCs.

RESULTS

Standard FNA allowed accurate diagnosis of malignancy in 32 of the 42 FVPTCs and in 170 of the 185 typical papillary thyroid cancers. TPO-immunohistochemistry staining was accurate in all 42 FVPTCs and in 182 of 185 typical PTCs.

CONCLUSIONS

FVPTC is a frequent source of false-negative results on standard thyroid FNA. This study shows that TPO immunostaining accurately demonstrates malignancy in these tumors.

Comparison of thyroid peroxidase expression with cellular proliferation in thyroid follicular tumors

Thyroid cancer is associated with abnormal thyroid peroxidase (TPO) expression as shown by abolition of immunodetection by monoclonal antibody 47 (Mab 47). The purpose of this study was to determine the relation of this abnormality with differentiation and proliferative potential of follicular tumors evaluated by analyzing thyroglobulin (TG) expression and proliferative cell nuclear antigen (PCNA) index. TPO, TG, and PCNA immunostaining were performed in a series of 30 thyroid follicular tumors ranging from adenoma to invasive carcinoma. Our findings confirmed that TPO abnormalities and PCNA index were correlated with malignancy, and that PCNA as well as TPO could be used to determine the growth potential of follicular proliferations in fine-needle aspirates. The most discriminant parameter was the ratio between the percentage of Mab-47 and PCNA positive cells. Ratios under 0.6 were correlated with malignancy in 90% of the cases, with only 3 cases of atypical adenomas being misdiagnosed as carcinomas. An inverse correlation was found between TPO and PCNA expression, but TG, which persisted at high levels in several actively growing follicular carcinomas, did not appear directly linked to cellular proliferation. These findings confirm that, unlike a decrease in TG synthesis that merely reflects the progressive loss of differentiation occurring in high-grade proliferations, alteration of TPO is an early marker of thyroid follicular tumors, closely related to acceleration of tumor growth in the first stages of malignant transformation.

Telomerase activity in benign and malignant thyroid tumors

Thyroid nodules are found in 5% to 10% of the population. While these nodules carry only a 5% to 10% risk of malignancy, tests that complement fine-needle aspiration (FNA) cytology in preoperative diagnosis and risk stratification are lacking. Telomerase is a ribonucleoprotein polymerase with activity found in many malignant tissues, but absent from most normal adult tissue. In this study, we have investigated telomerase activity in 24 thyroid tumors, 14 matched adjacent thyroid tissues, and 3 chronic thyroiditis tissue samples. Using a telomeric repeat amplification protocol (TRAP) assay on frozen tissue, telomerase activity was detected in 11 of 20 thyroid carcinomas, including 10 of 14 papillary carcinomas and a Hurthle cell carcinoma. Telomerase activity was not detected in 4 benign adenomas, 3 follicular carcinomas, or a single case each of medullary and anaplastic thyroid carcinoma. Telomerase activity was detected in 3 of 14 samples of adjacent thyroid tissue from patients with thyroid tumors. Interestingly, all 3 cases of adjacent thyroid tissue that tested positive had a moderate to marked degree of chronic inflammation. In addition, 3 of 3 samples from chronic thyroiditis specimens tested positive for telomerase activity. When tumor invasiveness (vascular and/or capsular) was compared with telomerase activity in papillary carcinomas, only 1 of 4 telomerase-negative tumors was invasive, while 6 of 10 of telomerase-positive tumors were invasive. Moreover, 6 of 7 invasive papillary carcinomas had telomerase activity. In summary, this is the first report of telomerase activity in thyroid tissue and nodules. This activity was detected in a large percentage of papillary thyroid carcinomas, but not benign adenomas, follicular carcinomas, or most normal thyroid tissue. Telomerase activity may also correlate with tumor invasiveness. Further studies will focus on larger numbers of tumors, metastatic tissue, and undifferentiated carcinomas, as well as application of this assay to products from fine-needle aspirates as a potential diagnostic and prognostic marker in thyroid neoplasms.

Immunohistochemical loss of thyroid peroxidase in papillary thyroid carcinoma: strong suppression of peroxidase gene expression

It is believed that qualitative changes in thyroid peroxidase (TPO) cause decreased enzyme activity in differentiated thyroid carcinoma. To re-evaluate TPO expression in thyroid cancer, TPO mRNA expression was compared with TPO protein expression in 38 samples of thyroid tissue obtained from patients with various thyroid diseases. In Northern blot studies, while TPO mRNA was highly expressed in tissues from all 18 benign lesions, it was strongly suppressed in 14 tumours, including 12 out of 12 papillary carcinomas, one of seven follicular carcinomas, and one medullary carcinoma. TPO mRNA was not detected in six carcinomas, of which four were papillary, one follicular, and one medullary, by the usual Northern blot method. The 14 cases with strong underexpression of TPO mRNA were very weakly stained with anti-TPO monoclonal antibody 38E, whereas all 18 benign tissues were strongly stained. Moreover, a comparative study of TPO expression by Northern blot and immunohistochemical analysis revealed a positive correlation between TPO mRNA expression and the staining intensity of TPO protein. These results suggest that strong suppression of TPO mRNA transcription causes low TPO activity in papillary carcinoma; immunohistochemical loss of TPO may be a useful diagnostic marker. TPO mRNA expression in differentiated thyroid carcinomas did not always correlate with the mRNA expression of thyroglobulin, thyroid stimulating hormone receptor, and thyroid transcription factor 1.