[Molecular Aspects of Thyroid Tumors with Emphasis on MicroRNA and Their Clinical Implications]

BACKGROUND

Central to neoplastic transformation and tumor progression is alteration of the signaling pathways that control cell proliferation and apoptosis. The key mechanisms for this neoplastic process are genetic changes (mutations of cancer-related genes) and recently identified epigenetic changes that involve DNA methylation, chromatin remodeling (which has a profound effect on the control of gene expression), and noncoding, regulatory RNA (notably, microRNA - miRNA). MiRNAs control expression of their target gene post-transcriptionally. These molecular factors have potential as diagnostic, prognostic, and predictive molecular markers. Epithelial tumors of the thyroid gland are a histogenetically, morphologically, and pathobiologically heterogeneous group of neoplasms and require new, molecular approaches in clinical practice.

AIM

This review aims to present contemporary scientific knowledge of this molecular (genetic and epigenetic) field of sporadic thyroid tumors of follicular cell origin and their potential clinical implications. The fundamental mutations (BRAFV600E, RET/PTC, RAS, and PAX8-PPARG) in selected tumor types are described comprehensively. Special attention is paid to miRNAs, including their biogenesis, function, and expression profiles in the most common thyroid tumors - follicular adenoma, follicular carcinoma, and papillary carcinoma.

CONCLUSION

Thyroid cancer medicine has recently entered a new, molecular era. Comprehensive knowledge of all molecular aspects may improve diagnostics and management of thyroid neoplasms through the introduction of novel, progressive treatment strategies for this cancer. Further research on signaling pathway-related targets, standardization of methods, and evaluation of results are required.Key words: thyroid tumors - cancerogenesis - genetics - epigenetics - microRNA The authors declare they have no potential conflicts of interest concerning drugs, products, or services used in the study. The Editorial Board declares that the manuscript met the ICMJE recommendation for biomedical papers.Submitted: 19. 10. 2016Accepted: 2. 11. 2016.

A core needle biopsy provides more malignancy-specific results than fine-needle aspiration biopsy in thyroid nodules suspicious for malignancy

BACKGROUND AND AIMS

The most commonly used diagnostic method for the preoperative diagnosis of thyroid nodules is ultrasound-guided fine-needle aspiration biopsy (FNA), which often yields non-diagnostic or non-definitive results and seldom produces definite malignant diagnoses. To improve upon the malignancy-specific sensitivity, we tested core needle biopsies (CNBs) of thyroid lesions taken from surgical specimens.

MATERIAL AND METHODS

52 consecutive patients with malignant or malignant-suspicious thyroid nodules were referred to Tampere University Hospital between May 2010 and December 2011. Preoperative FNAs were categorised as follicular neoplasm (48%), suspicion for malignancy (46%) or malignancy (6%). Intraoperative FNA and CNB samples were acquired from surgical specimens removed during surgery. The results of the needle biopsies were compared with the final pathological diagnosis.

RESULTS

CNBs had a high definitive sensitivity for malignancy (61%, CI 41% to 78%) whereas the definitive sensitivity for malignancy of FNAs was significantly lower (22%, CI 10% to 42%). CNB was not beneficial in the diagnosis of follicular thyroid lesions. When all suspected follicular tumours were excluded, the definitive sensitivity of CNB rose to 70% (CI 48% to 86%).

CONCLUSIONS

CNB may be beneficial for the diagnosis of papillary thyroid carcinoma and other non-follicular thyroid lesions. CNB may be considered as an additional diagnostic procedure in cases with FNA suspicious for malignancy.

Rising Incidence of Small Size Papillary Thyroid Cancers with No Change in Disease-Specific Survival in Finnish Thyroid Cancer Patients

Background:

The aim of this study was to investigate trends in the incidence, diagnostics, treatment and survival of thyroid cancer in Tampere University Hospital (TAUH) region in recent decades.

Material and Methods:

New thyroid cancer cases from 1981 to 2002 were ascertained from the Finnish Cancer Registry. Follow-up data was collected from medical records of TAUH. Differentiated thyroid cancer (DTC; consisting of papillary thyroid cancer (PTC) and follicular thyroid cancer (FTC)) patients' data was analyzed and divided into two equal time periods (1981–1991 and 1992–2002).

Results:

The total amount of thyroid cancer cases was 553, of which 427 (77%) were papillary and 72 (13%) follicular. Thyroid cancer was four times more common in females than in males and the median age at the time of diagnosis was 52 years. The incidence of DTC was 4.5/100 000 in the earlier group and 6.0/100 000 in the later group (IRR 1.33, CI 1.11–1.60). The proportion of papillary thyroid cancer rose from 81% to 89% (p = 0.02) in two study periods. Median tumour size became smaller, from 25 mm to 15 mm (p < 0.001). Surgery became more radical as total thyroidectomies were performed almost exclusively on the later group (p < 0.001). Median cumulative dose of radioiodine (I131) therapy was higher in the later group (p = 0.04). There was no difference in number of cancer recurrences (p = 0.54). The prognosis of DTC was good; 10-year disease-specific survival was 92% in the earlier group and 94% in the later group (p = 0.43).

Conclusions:

The incidence of thyroid cancer has risen and proportion of papillary cancer has increased, however, median size of tumour has decreased. No difference was seen in either all-cause or disease-specific survival.

[Lymphatic system: morphology and pathology update]

The lymphatic system is crucial for the maintenance of tissue fluid balance, immune surveillance, and fatty acids absorption in the intestine. The lymphatic vessels are also involved in the pathogenesis of tumor metastasis, lymphedema, and various inflammatory processes. Recently, several markers specific for lymphatic endothelium were found. Progress in the field of lymphatic growth factors and their receptors, and molecular lymphatic biology has helped to understand better the lymphatic vasculature. This review summarizes the updates on lymphatic system research and possible applications in routine pathological diagnostics.

[Pulmonary veins and atrial fibrillation: a pathological study of 100 hearts]

Pathogenesis of atrial fibrillation (AF), the most common sustained heart arrhythmia, is not yet fully elucidated. Recent electrophysiological studies have shown that in most patients with AF the arrhythmia is triggered by ectopic beats originating from extensions of left atrial myocardium over the pulmonary veins (PVs), so called myocardial sleeves (MSPV). A total of 100 hearts (393 PVs) obtained at autopsy were prospectively studied - 50 from patients with chronic AF (average age 76.9 +/- 7.3 yrs.) and a control group of 50 with a sinus rhythm (aver. age 71.7 +/- 9.5 yrs.). This is a largest study published on this topic so far. It appeared that MSPV frequently harbour pathological lesions, particularly senile atrial amyloid, and scarring. These two pathological changes were evaluated semiquantitatively on a grade 0-3 basis in individual PVs, comparing the results in the AF vs. the control group. Amyloidosis of MSPV was found in 68 % of all hearts and in 55 % of all sleeves. The deposits were most marked in the right superior PV. Amyloidosis was more frequent and more severe in MSPV of patients with AF (58.5 %; average grade 0.89) than of those without AF (51.7 %; aver. grade 0.76); the differences, however, lack statistical significance. Scarring of MSPV was present in all 349 sleeves, more markedly in the left inferior, left superior, and right superior PVs. It was significantly more severe in patients with AF compared to those without the arrhythmia. By an injection metod, we have shown that MSPV are supplied by coronary arteries. However, the degree of scarring of the sleeves did not correlate with the degree of coronary atherosclerosis. We suggest that genesis of the scarring is not postnecrotic but degenerative, due to diffuse hypoxia of the sleeve myocardium. To conclude, amyloidosis and particularly scarring of MSPV appear generally in the elderly population as an arrhythmogenic substrate for AF.

Amyloid in the cardiovascular system: a review

The cardiovascular system is a common target of amyloidosis. This review presents the current clinical and diagnostic approach to amyloidosis, with the emphasis on cardiovascular involvement. It summarises recent nomenclature, classification, and pathogenesis of amyloidosis. In addition, non-invasive possibilities are discussed, together with endomyocardial biopsies in the diagnosis of cardiac amyloidosis. Finally, recent advances in treatment and prognostic implications are presented.

Intestinal spirochaetosis: a rare histopathological diagnosis and potential light microscopic pitfall

A case of intestinal spirochaetosis is described. Endoscopic specimens of a 52-year-old female revealed a blue basophilic margin of mucosal surface in haematoxylin-eosin stained sections. However, on ultrastructural level, moderate infestation of enterocytic brush border with spirochaetes was found. The pitfalls of histopathological diagnosis of spirochaetosis are discussed.

[Thyroid peroxidase in the differential diagnosis of thyroid gland lesions. A marker of biological behavior or differentiation?]

Human thyroid peroxidase (hTPO) is a membrane protein with a key role in the thyroid hormones synthesis. Loss of hTPO was described in malignant tumours of the thyroid gland. hTPO was tested as a marker of malignancy. Immunohistochemical study of hTPO in 321 thyroid lesions (45 malignant tumours, 72 benign tumours, 199 benign non-tumours lesions, and 5 normal thyroid glands) is presented. The sensitivity of hTPO in predicting malignancy in thyroid is 64%, and the specificity is 87%. Thus, hTPO is of limited value in the diagnosis of thyroid malignancy. The authors discuss the role of hTPO as a marker of differentiation.

Immunohistochemical detection of dipeptidyl peptidase IV (CD 26) in thyroid neoplasia using biotinylated tyramine amplification

Differential diagnosis between malignant and benign thyroid tumors derived from follicular cells can pose certain difficulties in routine surgical pathology. The aim of the study was to evaluate dipeptidyl peptidase IV (DPP IV/CD 26) in differential diagnostics of thyroid lesions. DPP IV/CD 26 was evaluated in thyroid glands of 309 patients (261 females and 48 males, age range of patients 15-80 years). DPP IV/CD 26 was assessed in paraffin-embedded thyroid specimens immunohistochemically using commercially available antibody (Serotec) and biotinylated tyramine amplification kit (DAKO). Well-differentiated carcinoma revealed DPP IV/CD 26 positivity in 33 out of 42 cases (79%). Neither medullary nor insular carcinoma was DPPIV/CD 26 positive (only one case of each tested). DPPIV/CD 26 expression in isolated cells was seen in 18/261 (7%) benign disorders. The sensitivity of the method was 68%, the specificity was 94%, and the diagnostic accuracy was 91%, respectively, using 5% threshold of positive follicular cells. DPP IV/CD 26 can be assessed immunohistochemically using biotinylated tyramine amplification kit. DPP IV/CD 26 could be an adjunct in the thyroid gland differential diagnosis. However, DPP IV/CD 26 positivity is limited to the group of well-differentiated carcinomas, particularly papillary carcinoma. Furthermore, it is of limited value for follicular and oncocytic tumors.

[Dipeptidyl peptidase IV (DPP IV, CD 26): a tumor marker in cytologic and histopathologic diagnosis of lesions of the thyroid gland]

BACKGROUND

Morphological diagnostics of thyroid gland tumours faces certain differential diagnostic problems. Extensive histological examination of the entire tumour is required for the final diagnosis of follicular and oncocytic tumours. Thus, assessment of reliable definitive cytological and/or intraoperative histological diagnosis is not possible. No marker of malignancy has been so far generally accepted in the thyroid tumour diagnosis. The aim of the study was to evaluate membrane protease dipeptidyl peptidase IV (DPP IV) in the differential diagnosis of thyroid tumours.

METHODS AND RESULTS

DPP IV was assessed cytochemically in 254 smears, histochemically in 314 cryostat sections, and immunohistochemically in 309 paraffin-embedded sections obtained from the group of 336 patients. There were 283 females and 53 males with the mean age of 48 years (range 15-80 years) in this series. Sensitivity of cytochemical detection was 71%, specificity was 96%, and diagnostic accuracy was 93% using the 50% threshold. Histochemically, sensitivity was 71%, specificity was 93%, and diagnostic accuracy was 90% using the 5% threshold. Using the immunohistochemical assessment, sensitivity was 68%, specificity was 94%, and diagnostic accuracy was 91% using the 5% threshold.

CONCLUSIONS

According to our results, DPP IV can be used as a marker of malignancy in well-differentiated carcinomas of follicular cell origin, namely in papillary carcinoma. However, it is less reliable in follicular and oncocytic carcinomas.

Diagnostic role of markers dipeptidyl peptidase IV and thyroid peroxidase in thyroid tumors

BACKGROUND

In seeking to improve the differential diagnosis between malignant and benign thyroid tumors of follicular cell origin, we assessed the expression of dipeptidyl peptidase IV (DPP IV) and thyroid peroxidase (TPO). DPP IV is a membrane peptidase expressed in many human tissues, excluding the normal thyroid gland. However, aberrant expression has been described in thyroid carcinomas. TPO is an essential enzyme in the biosynthesis of thyroid hormones with various types of expression in pathological thyroid lesions.

MATERIALS AND METHODS

A total of 151 thyroid glands were examined: 24 malignant tumors, 29 benign tumors, 98 benign lesions and 5 normal glands. DPP IV expression was analyzed by a histochemical technique in both frozen sections and imprint/aspirate smears. TPO was assessed immunohistochemically in paraffin-embedded specimens.

RESULTS

DPP IV sensitivity in frozen section was 56% and its specificity was 99%, in both cases with a 50% threshold. In cytology, the sensitivity was 68% and the specificity was 98% using the 50% threshold. TPO sensitivity and specificity was 64% and 99%, respectively. The sensitivity and specificity of both markers was 92% and 94%, respectively.

CONCLUSION

We recommend adding DPP IV and TPO to the list of diagnostic tumor markers for malignant thyroid tumors of follicular cell origin.

Dipeptidyl peptidase IV expression in thyroid cytology: retrospective histologically confirmed study

Fine needle aspiration cytology (FNAC) of the thyroid gland is a well-established method. However, it has inherent limitations, especially in the diagnosis of follicular and oncocytic tumours and in distinguishing between nuclear atypia in colloid goitre with regressive changes and cystic papillary carcinoma. The aim of our study was to evaluate dipeptidyl peptidase IV (DPP IV) as a marker of malignancy in FNAC. We tested 254 thyroid specimens (intraoperative imprint smears) for DPP IV. The sensitivity was 71%, the specificity was 96%, and the diagnostic accuracy was 93%, respectively, with a threshold of 50% of positive cells. To the best of our knowledge it is the largest histologically confirmed study reported in the literature. We suggest the assessment of DPP IV as an adjunct diagnostic marker of malignancy in thyroid specimens suspicious of papillary carcinoma. However, the value of the marker in follicular lesions is very limited.

[Interpretation of a biopsy of Vater's papilla--normal histologic structure]

The normal histological study of the papilla of Vater is presented. The wide spectrum of normal histology is described in the autopsy material and the differential diagnosis between uneasy interpretable normal and pathologic structures is discussed.

[Secondary changes in the thyroid gland induced by aspiration cytology]

Due to the introduction of fine needle aspiration cytology (FNAC) to the routine clinical preoperative examination surgical pathologists are faced with thyroid gland specimens with FNAC-induced secondary changes. These changes can cause diagnostic difficulties and be a source of incorrect diagnosis. Authors present a review of FNAC-induced changes with differential diagnostic criteria helpful in these pitfalls. FNAC-induced changes can be schematically divided into two major groups--recent ones (intranodal bleeding and/or necrosis) and subacute/late ones (proliferation of granulation tissue with predominance of myofibroblasts or endothelial cells, resorptive pseudoxantomathous granulomas, formation of sarcoid-like granulomas, capsular pseudoinvasion and scarring). Pathologists should be informed about the previously performed FNAC and must be aware of these lesions to prevent their misinterpretation.

[Dipeptidyl(amino)peptidase IV in the differential diagnosis of thyroid gland tumors: methods and results of a pilot study of 200 cases]

The use of dipeptidyl aminopeptidase IV (DPP IV) staining by azo-coupling in preoperative and intraoperative diagnostics of thyroid lesions is presented. In a series of 200 histologically confirmed cases examined, the sensitivity and the specificity were 71% and 99%, respectively in 124 smears, and 70% and 94%, respectively in 189 frozen sections. DPP IV expression showed high negative predictive value as well. DPP IV is suggested as an additional tool in the preoperative and intraoperative diagnostics of thyroid lesions.

[Pulmonary embolism in children and adolescents]

We present a necropsy study of 25 children (age 0-15 years) and 7 adolescents (age 16-18 years) with the diagnosis of macroscopic pulmonary thromboembolism (PTE). PTE occurred along with a serious disease, e.g. tumour or general infection, and when the subjects had some of the following risk factors, e.g. immobilization, tumours, cardiovascular diseases, operations, obesity, septic state, peritonitis, cachexia and placement of central venous catheters.

Composite Tumor Consisting of Dermatofibrosarcoma Protuberans and Giant Cell Fibroblastoma Associated with Intratumoral Endometriosis

We present a unique case of composite skin tumor of the vulva consisting of dermatofibrosarcoma protuberans (DFSP) and giant cell fibroblastoma (GCF) with an intratumoral focus of endometriosis. A 31-year-old female with a 10-year-history of a recurring subcutaneous tumor in the vulvar area underwent excision of the seventh recurrence of the tumor. Microscopic examination revealed a composite fibrohistiocytic tumor consisting of DFSP and GCF. Additionally, a focus of endometriosis within the tumor tissue was found. Malignant transformation of extragonadal endometriosis has already been described; we present, however, the occurrence of a focus of endometriosis within the tissue of a hormonally independent soft tissue tumor. There is a possible link to the occurrence of cutaneous endometriosis at previous surgery sites and in the scars. The presence of endometriosis within the soft tissue tumor represents, to the best of our knowledge, a previously undescribed collision phenomenon.