Poorly differentiated oxyphilic (Hurthle cell) carcinomas of the thyroid

Somatostatin and Somatostatin Receptors in Tumour Biology

Somatostatin (SST), a growth hormone inhibitory peptide, is expressed in endocrine and non-endocrine tissues, immune cells and the central nervous system (CNS). Post-release from secretory or immune cells, the first most appreciated role that SST exhibits is the antiproliferative effect in target tissue that served as a potential therapeutic intervention in various tumours of different origins. The SST-mediated in vivo and/or in vitro antiproliferative effect in the tumour is considered direct via activation of five different somatostatin receptor subtypes (SSTR1-5), which are well expressed in most tumours and often more than one receptor in a single cell. Second, the indirect effect is associated with the regulation of growth factors. SSTR subtypes are crucial in tumour diagnosis and prognosis. In this review, with the recent development of new SST analogues and receptor-specific agonists with emerging functional consequences of signaling pathways are promising therapeutic avenues in tumours of different origins that are discussed.

No Longer Well-Differentiated: Diagnostic Criteria and Clinical Importance of Poorly Differentiated/High-Grade Thyroid Carcinoma

Poorly differentiated thyroid carcinoma (PDTC) and differentiated high-grade thyroid carcinoma (DHGTC) are uncommon thyroid malignancies, recently (re)codified into distinct entities with overlapping clinical significance. Recognizing them may be challenging for the general practitioner and subspecialty pathologist alike. This article will describe the required features to diagnose PDTC and DHGTC, differential diagnostic considerations, molecular findings, and clinical implications. It is intended to be a general synopsis of the most critical elements of PDTC and DHGTC as well as a summary of points in approaching these challenging cases.

High-Grade Non-Anaplastic Thyroid Carcinomas of Follicular Cell Origin: A Review of Poorly Differentiated and High-Grade Differentiated Carcinomas

Poorly differentiated thyroid carcinoma (PDTC) and high-grade differentiated thyroid carcinoma (HGDTC) are considered high-grade follicular-derived thyroid carcinomas, with prognoses intermediate between well-differentiated and anaplastic thyroid carcinoma. Both share the presence of invasion, thyroid follicular-cell origin, and tumor necrosis or increased mitoses (≥ 3 mitoses per 2 mm² in PDTC and ≥ 5 mitoses per 2 mm² in HGDTC), without anaplastic dedifferentiation. PDTC must possess solid, trabecular, or insular growth and lack classic papillary-like nuclei; HGDTC can be of any architectural or nuclear morphology (follicular-like, papillary-like, oncocytic). Transformation may be accompanied by acquisition of high-risk mutations (such as TP53 or TERT promoter) on top of RAS-like or BRAF p.V600E-like (including NTRK-fusion) initial driver mutations. These carcinomas most frequently affect adults and often present with metastases (20-50%) or wide local invasion. As PDTC and HGDTC may be radioactive iodine resistant, post-surgical therapy may consist of external beam radiotherapy or targeted, mutation-dependent chemotherapy, such as tyrosine kinase inhibitors. Ten-year disease specific survival is as low as 50%. Awareness of high-grade features in the diagnostic setting is important for patient prognosis and triage of tissue for molecular analysis in order to guide relevant clinical management and therapy.

Oncocytic Papillary Thyroid Carcinoma and Oncocytic Poorly Differentiated Thyroid Carcinoma: Clinical Features, Uptake, and Response to Radioactive Iodine Therapy, and Outcome

OBJECTIVE

The main objective of this study was to review the clinicopathologic characteristics and outcome of patients with oncocytic papillary thyroid carcinoma (PTC) and oncocytic poorly differentiated thyroid carcinoma (PDTC). The secondary objective was to evaluate the prevalence and outcomes of RAI use in this population.

METHODS

Patients with oncocytic PTC and PDTC who were treated at a quaternary cancer centre between 2002 and 2017 were retrospectively identified from an institutional database. All patients had an expert pathology review to ensure consistent reporting and definition. The cumulative incidence function was used to analyse locoregional failure (LRF) and distant metastasis (DM) rates. Univariable analysis (UVA) was used to assess clinical predictors of outcome.

RESULTS

In total, 263 patients were included (PTC [n=218], PDTC [n=45]) with a median follow up of 4.4 years (range: 0 = 26.7 years). Patients with oncocytic PTC had a 5/10-year incidence of LRF and DM, respectively, of 2.7%/5.6% and 3.4%/4.5%. On UVA, there was an increased risk of DM in PTC tumors with widely invasive growth (HR 17.1; p<0.001), extra-thyroidal extension (HR 24.95; p<0.001), angioinvasion (HR 32.58; p=0.002), focal dedifferentiation (HR 19.57, p<0.001), and focal hobnail cell change (HR 8.67, p=0.042). There was additionally an increased risk of DM seen in male PTC patients (HR 5.5, p=0.03).The use of RAI was more common in patients with larger tumors, angioinvasion, and widely invasive disease. RAI was also used in the management of DM and 43% of patients with oncocytic PTC had RAI-avid metastatic disease. Patients with oncocytic PDTC had a higher rate of 5/10-year incidence of LRF and DM (21.4%/45.4%; 11.4%/40.4%, respectively). Patients with extra-thyroidal extension had an increased risk of DM (HR 5.52, p=0.023) as did those with angioinvasion. Of the patients with oncocytic PDTC who received RAI for the treatment of DM, 40% had RAI-avid disease.

CONCLUSION

We present a large homogenous cohort of patients with oncocytic PTC and PDTC, with consistent pathologic reporting and definition. Patients with oncocytic PTC have excellent clinical outcomes and similar risk factors for recurrence as their non-oncocytic counterparts (angioinvasion, large tumor size, extra-thyroidal extension, and focal dedifferentiation). Compared with oncocytic PTCs, the adverse biology of oncocytic PDTCs is supported with increased frequency of DM and lower uptake of RAI.

The Oncocytic Variant of Poorly Differentiated Thyroid Carcinoma Shows a Specific Immune-Related Gene Expression Profile

BACKGROUND

Poorly differentiated thyroid cancer (PDTC) is a rare, follicular cell-derived neoplasm with an unfavorable prognosis. The oncocytic variant of PDTC may be associated with even more adverse outcome than classical PDTC cases, but its specific molecular features are largely unknown. Our aim was to explore the immune-related gene expression profile of oncocytic and classical PDTC, in correlation with clinical and pathological characteristics (including programmed death ligand 1 [PD-L1] expression) and outcome, and in comparison with a control group of well-differentiated follicular carcinomas (WDFCs), including conventional follicular carcinomas (FTCs) and Hürthle cell carcinomas (HCCs).

METHODS

A retrospective series of 48 PDTCs and 24 WDFCs was analyzed by means of NanoString technology employing the nCounter PanCancer Immune Profiling panel. Gene expression data were validated using quantitative real-time polymerase chain reaction.

RESULTS

Oncocytic PDTCs showed a specific immune-related gene expression profile, with higher expression of LAIR2, CD274, DEFB1, IRAK1, CAMP, LCN2, LY96, and APOE, and lower expression of NOD1, as compared to conventional PDTCs. This molecular signature was associated with increased intratumoral lymphocytic infiltration, PD-L1 expression, and adverse outcome. Three of these genes, CD274, DEFB1, and IRAK1, as well as PD-L1 expression, were also the hallmarks of HCCs as compared to FTCs. By contrast, the panel of genes differentially regulated in PDTCs as compared to WDFCs was unrelated to the oncocytic phenotype.

CONCLUSIONS

Our results revealed a distinctive immune-related gene expression profile of oncocytic PDTC and confirmed a more aggressive outcome in this cancer subtype. These findings may provide guidance when exploring novel immunotherapeutic options for oncocytic PDTC patients.

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.

The Relationship of Immunoexpression of Ki-67 and Hsp70 with Clinical and Morphological Parameters and Prognosis of Papillary Thyroid Cancer

We studied the correlations of the expression of Ki-67 proliferation marker and localization of heat shock protein Hsp70 in tumor cells of papillary thyroid cancer with some clinical and morphological parameters and a 10-year survival prognosis. High variability of the proliferative activity (by Ki-67 index) of tumor cells was revealed. It was found that Hsp70 protein has different localization in tumor cells: cytoplasmic, nuclear, nucleolar, and mixed. Nuclear translocation of the Hsp70 protein correlated with the stage of the process and the prognosis of the disease, but did not correlate with sex, tumor size, capsule invasion, and lymph node metastasis. Ki-67 index of tumor cells correlated with sex, stage of the process, size of tumor formation and prognosis, but did not correlated with age, invasion into the capsule and metastasis to the lymph nodes. Depending on the variants of Hsp70 and Ki-67 co-expression, three molecular types of papillary thyroid cancer can be distinguished: favorable, intermediate, and poor prognosis.

Oncocytic poorly differentiated (insular) thyroid carcinoma mimicking metastatic adenocarcinoma. A case report and review of the literature

We report the cytohistologic and immunohistochemical findings of an oncocytic variant of poorly differentiated thyroid carcinoma in a 76-year old man with a prior history of prostatic adenocarcinoma. The man complained of a palpable nodule in the right thyroid lobe and cervical lymph node. Fine-needle aspiration (FNA) in both cases yielded solid clusters of cells/insulae, microfollicles, and isolated atypical cells. Considering the patient's past history, an initial diagnosis of metastasis from prostate adenocarcinoma was considered. However, immunohistochemical staining of liquid-based cytology specimens (Thin-Prep) showed diffuse positive results for TTF-1 and thyroglobulin. The patient underwent total thyroidectomy with bilateral neck dissection. Histologic and immunohistochemical evaluation showed a poorly differentiated oncocytic thyroid carcinoma with lymphovascular invasion and lymph node metastases. To our knowledge, this is the first description of the immunocytochemical evaluation of this rare variant of poorly differentiated thyroid carcinoma using FNA and liquid based cytology.

Oncocytic variant of poorly differentiated thyroid carcinoma: "Is diagnosis possible by fine-needle aspiration?"

Poorly differentiated thyroid carcinoma (PDTC) is a very rare entity, and the diagnosis can be made on histopathology specimens. However, recognition of characteristic features of PDTC is significant on fine-needle aspirations (FNAs) to differentiate this entity from well-differentiated and anaplastic thyroid carcinomas. Here, we present an FNA case concordant with “oncocytic variant of PDTC” and discuss whether definitive diagnosis can be given on FNAs to assess the prognosis in clinically inoperable patients.

The story of poorly differentiated thyroid carcinoma: From Langhans' description to the Turin proposal via Juan Rosai

Rosai, reinterpreting Langhans' "proliferating goiter," adopted the term "poorly differentiated carcinoma" for a specific thyroid tumor with insular features 30 years ago. This tumor type is only one of those approached by Dr. Rosai in the thyroid field (a PubMed search as of August 31, 2015 on "Rosai & thyroid" disclosed 73 articles), but seems the most innovative and representative of his heavy contribution to thyroid tumor classification. The diagnostic problems associated with PDTC recognition date back a long time, with a still ongoing debate on the nature of PDTC, its morphological diagnostic features, its clinical significance, and its optimal therapeutic approach. In 2004, PDTC was at last incorporated in the WHO classification of thyroid tumors, but the proposed diagnostic criteria were heterogeneous, controversial, and hardly applicable in the diagnostic practice. A consensus conference held in Turin in 2006 was lead by the authors and Dr. Rosai and confirmed the presence of geographical differences among claimed classical PDTC forms, which were responsible for a poor interobserver reproducibility of the diagnostic criteria. A diagnostic algorithm was therefore designed to define the crucial parameters to categorize PDTC and better stratify these distinctly aggressive tumors.

Hurthle Cell Lesion: Controversies, Challenges, and Debates

Hurthle cell lesion is one of the most questionable clinico-pathological entities in most of its aspects. Literature has used the terms oncocytic, oxyphilic, Hurthle, and Ashkanazy interchangeably; what does each term denote? Who first described these cells? What is the cell of origin? How much Hurthle cells should be present to define the lesion as Hurthle cell one? Is it possible to differentiate hyperplastic from neoplastic and benign from malignant Hurthle cell lesion on a non-histopathologic ground? Does it belong to follicular or to papillary neoplasms or should it be classified separately? Can we anticipate its clinical behavior or predict its outcome? How can we manage? We will try to answer these questions in light of the ongoing relevant arguments with the aim of resolving some uncertainties and suggesting how to solve others.

PTEN and TP53 Mutations in Oncocytic Follicular Carcinoma

Oncocytic follicular carcinoma (OFC)/Hürthle cell carcinoma represents 3-4 % thyroid carcinomas and can be associated with more aggressive behavior and compromised survival compared to non-oncocytic thyroid carcinoma. In this study, we utilized targeted next-generation sequencing to investigate the molecular alterations in a heterogeneous group of clinically aggressive OFC. A total of 12 cases of OFC were included in this study. Targeted next-generation sequencing was performed using panels of 47 or 20 genes, which are frequently mutated in solid tumors. The case cohort comprised eight cases of angioinvasive OFC, two cases of poorly differentiated OFC, one case of OFC with anaplastic change, and one case of OFC with capsular invasion only. Five out of 12 cases (42 %) harbored TP53 mutation. PTEN mutations were also seen in three cases with TP53 mutation (25 %). Based on this study, TP53 and PTEN are possibly involved in the pathogenesis of OFC. Further studies on a larger case cohort are needed to further elucidate this mechanism and its effect on clinical behavior of these intriguing tumors.

Poorly differentiated oncocytic (hürthle cell) follicular carcinoma: an institutional experience

The proposed diagnostic criteria for poorly differentiated thyroid carcinoma (known as the Turin classification) were defined based on growth pattern (solid, trabecular, or insular) and high-grade morphologic features (nuclear pleomorphism, mitoses including abnormal forms, and coagulative tumor necrosis). The development of this classification specifically did not include tumors with oncocytic or Hürthle cell cytology, and only sparse literature describing poorly differentiated oncocytic carcinomas is available. In this study, we examined a cohort of 284 cases of oncocytic follicular carcinoma/Hürthle cell carcinoma (OFC/HCC) and identified 17 cases of oncocytic variant of poorly differentiated carcinoma (OV-PDTC) based on Turin criteria. Compared to minimally invasive and angioinvasive OFC/HCC, these tumors arose in older patients (range 44-88 years; average 71 years), were larger (average size 4.5 cm), and all had extensive vascular invasion (5-15 foci), and coagulative tumor necrosis and the tumor cells were arranged in a trabecular or solid growth pattern. All showed an admixture of oncocytic follicular/Hürthle cells arranged in solid and trabecular growth pattern. Aggregates of small sized cells with minimal eosinophilic cytoplasm, comprising 10-20% of the entire tumor mass were also seen in 16/17 cases. Clinical follow-up was available in 12 cases and ranged from 6 to 120 months (average 41 months). Distant metastases were seen in 10/12 (83%) patients; two had lung and one had bone metastases at the time of thyroid surgery, and four subsequently developed cervical lymph node metastases. Two patients died of disease, and ten are alive either with or free of tumor. The OV-PDTC is a distinct entity which can be identified based on Turin criteria and the presence of a distinct "small cell" component. It is frequently associated with regional recurrence and distant metastases and can lead to tumor-related demise.

Poorly Differentiated Thyroid Carcinoma

Poorly differentiated thyroid carcinoma (PDTC) has been recognized for the past 30 years as an entity showing intermediate differentiation and clinical behavior between well-differentiated thyroid carcinomas (ie, papillary thyroid carcinoma and follicular thyroid carcinoma) and anaplastic thyroid carcinoma; however, there has been considerable controversy around the definition of PDTC. In this review, the evolution in the definition of PDTC, current diagnostic criteria, differential diagnoses, potentially helpful immunohistochemical studies, and molecular alterations are discussed with the aim of highlighting where the diagnosis of PDTC currently stands.

Aggressive variants of follicular cell derived thyroid carcinoma; the so called 'real thyroid carcinomas'

The pathological diagnoses and classification schemes for thyroid carcinoma have changed over the past 20 years and continue to do so. New entities have been described and molecular analyses have suggested better characterisation and grouping of certain tumours. Because some of the lesions have been named differently by different authors, clinicians and patients may be confused as to what a specific patient's lesion represents. In this review, we discuss the thyroid tumours of follicular origin which are clinically unusual but important to recognise as their behaviour may be aggressive, they may not respond to radioiodine treatment and they may cause significant mortality. This paper describes these important but rare lesions, their pathological features, important clinicopathological correlations, molecular correlates and prognostic implications.

Poorly differentiated oncocytic thyroid carcinoma--diagnostic implications and outcome

AIMS

  Poorly differentiated thyroid carcinomas (PDTC) are an ongoing diagnostic challenge. Although the Turin consensus criteria for PDTC excluded consideration of oncocytic tumours, the World Health Organization (WHO) classification does recognise an oncocytic variant of conventional PDTC. The aims of this study were to establish whether the Turin criteria can be applied to oncocytic PDTC, and to determine if there are prognostic differences between conventional and oncocytic PDTC.

METHODS AND RESULTS

  We applied the Turin criteria to 129 thyroid carcinomas. We identified 18 oncocytic PDTC and 16 conventional PDTC. Kaplan-Meier analysis revealed a significantly worse outcome for oncocytic PDTC with regard to overall and tumour-specific survival but no difference for relapse-free survival, all of which were confirmed by multivariate analysis. There was no association of survival with gender, age or tumour stage.

CONCLUSIONS

  The Turin criteria can be applied to oncocytic PDTC and patients with this variant have a decreased survival using conventional radioiodine treatment compared to conventional PDTC and might therefore be candidates for novel treatment modalities.

Uptake of (18) FDG by a Hepatic Adenoma on Positron Emission Tomography

Fluorodeoxyglucose positron emission tomography (¹⁸FDG-PET) is currently the best noninvasive test to confirm hepatic metastases when diagnostic uncertainty exists after initial imaging with first-line modalities. However, we report the second case of “false-positive” uptake of ¹⁸FDG on PET scanning from a histopathologically confirmed hepatic adenoma.

Poorly differentiated thyroid carcinoma. Are we there yet?

The article reviews the controversial area of poorly differentiated thyroid carcinoma. Consensus criteria that define poorly differentiated thyroid carcinoma have been published in 2007. According to these, poorly differentiated thyroid carcinoma is a distinct histotype and the term "poorly differentiated" should not be used as a synonym for high-grade thyroid cancer. Data in the literature show that tumor necrosis and high mitotic activity, but not growth pattern or histologic subtype, are prognostic markers for thyroid tumors. This underscores the importance of grading to identify thyroid carcinomas that behave aggressively. The issue of grading versus typing thyroid tumors is discussed.

Poorly differentiated carcinoma of the thyroid: validation of the Turin proposal and analysis of IMP3 expression

The Turin Proposal algorithm defines poorly differentiated carcinoma on the basis of the presence of solid/trabecular/insular growth pattern, absence of conventional nuclear features of papillary carcinoma, and the presence of at least one of the following features: convoluted nuclei, mitotic activity > or =3/10 HPF, or tumor necrosis. IMP3 appears to have diagnostic and prognostic value in many solid tumors, including thyroid carcinomas. We examined a series of follicular-cell carcinomas with prominent solid patterns diagnosed at Mayo Clinic (56 cases) (Rochester, MN, USA) and at the University of Turin (96 cases) (Northern Italy) to validate the Turin consensus criteria defining poorly differentiated carcinoma of the thyroid and to evaluate the prevalence and prognostic behavior of this tumor. On this series, we analyzed the expression of conventional markers by immunohistochemistry and we investigated the expression of IMP3 by both immunohistochemistry and qRT-PCR. The prevalence of poorly differentiated carcinoma among the USA cases was 1.8% (56/3128) and that in the cases of Northern Italy was 6.7% (96/1442). Tumor characteristics were similar in the cases from the USA and from Italy except for extensive vascular invasion and a prevalent insular growth pattern (lower the former, higher the latter in the Italian series). In univariate analysis, the risk of death was higher for age > or =45, tumors > or =4 cm, and IMP3 positivity. Multivariate analysis showed that the risk of death from poorly differentiated carcinoma was higher for age > or =45. The Turin consensus criteria can reliably select poorly differentiated carcinomas. Tumors from the USA and from Italy showed similar overall survival, although the prevalence of poorly differentiated carcinoma was higher in Northern Italy. Expression of IMP3 appears to be an adverse prognostic factor for poorly differentiated thyroid carcinoma.

Poorly differentiated thyroid carcinoma: 5 years after the 2004 WHO classification of endocrine tumours

Poorly differentiated thyroid carcinoma (PDTC) was originally described in 1983 but included in the WHO classification of thyroid tumours in the 2004 edition, only. The diagnostic problems encountered in the 5 years of application of the WHO criteria are reviewed here. A long debate is still going on about the nature of PDTC, its morphological diagnostic features, its clinical significance and its optimal therapeutic approach. A consensus conference held in Turin in 2006 confirmed the geographical differences among claimed classical forms of PDTC and suggested a diagnostic algorithm based on the presence of a solid/trabecular/insular growth pattern and of high-grade features, in line with the WHO definition of PDTC, capable to select tumours with a distinct aggressive clinical behaviour. This worked well for PDTC cases from mountain areas (e.g. Northern Italy), where most, if not all, thyroid carcinomas having high-grade features also share a solid/trabecular/insular pattern of growth. However, this scheme might be less easily applicable for American and Japanese cases, possibly due to heterogeneous architectural and cytological features; indeed some Authors still prefer to base their diagnostic work up on the recognition of high-grade features only, including mitotic index and necrosis, irrespective of the growth pattern.

The Thyroid Hürthle (Oncocytic) Cell and Its Associated Pathologic Conditions: A Surgical Pathology and Cytopathology Review

Context.—Hürthle cells are eosinophilic, follicular-derived cells that are associated with a variety of nonneoplastic and neoplastic thyroid lesions. The differential diagnosis of Hürthle cell lesions is quite broad.

Objective.—To review the pathologic conditions associated with Hürthle cells in the thyroid and to discuss pathology of thyroid lesions associated with oncocytic cytology.

Data Sources.—A variety of thyroid nonneoplastic (autoimmune thyroiditis, multinodular goiter) and neoplastic conditions (Hürthle cell adenoma, Hürthle cell carcinoma) are associated with Hürthle cell cytology. In addition, there are several thyroid neoplasms that should be considered when one observes a Hürthle cell neoplasm in the thyroid (oncocytic variant of medullary carcinoma, several variants of papillary thyroid carcinoma).

Conclusions.—Oncocytic cytology is seen in a variety of thyroid conditions that are associated with a broad differential diagnosis and care must be used for accurate diagnosis. Newer molecular-based techniques may be useful for further classification of thyroid neoplasms with oncocytic pathology.

Older age and larger tumor size predict malignancy in hürthle cell neoplasms of the thyroid

BACKGROUND

Hürthle cell neoplasms (HCNs) are rare tumors of the thyroid gland. The definitive treatment for Hürthle cell carcinoma (HCC) is total thyroidectomy, while thyroid lobectomy is adequate for Hürthle cell adenoma (HCA). However, differentiating HCC from HCA either before or during surgery is a challenge. The purpose of this study was to identify factors that predict malignancy in patients with HCN.

METHODS

Between May 1994 and January 2007, 1,199 patients underwent thyroid surgery at an academic medical center. Medical records of 55 consecutive patients who underwent thyroid resections for the preoperative diagnosis of HCN were reviewed.

RESULTS

Of the 55 patients with HCN, 46 (84%) had adenomas and 9 (16%) had carcinomas. Patients with HCC were significantly older than those with HCA (66 +/- 6 years versus 53 +/- 2 years, P = 0.01). Patients with carcinoma also had significantly larger thyroid nodules (4.5 +/- 0.7 cm versus 2.5 +/- 0.2 cm, P < 0.001). All HCNs less than 2 cm in diameter were benign. The malignancy rate increased with nodule size: 18% of nodules measuring 2-4 cm, and 44% of those larger than 4 cm were HCC. One patient with HCC had recurrence of the disease, but there were no disease-related deaths.

CONCLUSION

Advanced patient age and larger nodule size are two important factors that predict malignancy in patients with HCN. In patients with these and other known risk factors for HCC, total thyroidectomy should be considered.

Poorly differentiated thyroid carcinoma: diagnostic features and controversial issues

Poorly differentiated thyroid carcinomas are a heterogeneous group of tumors occupying an area intermediate between well-differentiated follicular or papillary carcinoma and anaplastic carcinomas, from both a histopathogenetic and a clinical point of view. Large tumor series selected on the basis of structural and/or other morphological criteria showed that poorly differentiated carcinomas have a distinct biological behavior, and the classification of these tumors into a separate group appears justified, although strict homogeneous diagnostic criteria should be achieved and widely accepted to better characterize such tumor entity. Moreover, the identification of the prognostic parameters segregating aggressive from indolent cases has important clinical implications. Molecular data in the literature, although limited by the heterogeneous case series analyzed, identify ras alterations as the most common molecular alteration in poorly differentiated carcinomas, thus, depicting a peculiar molecular pathway in this tumor type as compared to well-differentiated follicular and papillary carcinomas. The present paper aims to review the various aspects of this tumor type, from morphology to immunohistochemistry and molecular abnormalities from a practical and daily practice-oriented point of view.

Poorly Differentiated Thyroid Carcinoma: The Turin Proposal for the Use of Uniform Diagnostic Criteria and an Algorithmic Diagnostic Approach

Poorly differentiated (PD) thyroid carcinomas lie both morphologically and behaviorally between well-differentiated and undifferentiated (anaplastic) carcinomas. Following the original description of this entity, different diagnostic criteria have been employed, resulting in wide discrepancies and confusion among pathologists and clinicians worldwide. To compare lesions occurring in different geographic areas and the diagnostic criteria applied in those countries, we designed a study with a panel of internationally recognized thyroid pathologists to develop consensus diagnostic criteria for PD carcinomas. Eighty-three cases were collected from Europe, Japan, and the United States, and circulated among 12 thyroid pathologists. Diagnoses were made without any knowledge of the clinical parameters, which were subsequently used for survival analysis. A consensus meeting was then held in Turin, Italy, where an agreement was reached concerning the diagnostic criteria for PD carcinoma. These include (1) presence of a solid/trabecular/insular pattern of growth, (2) absence of the conventional nuclear features of papillary carcinoma, and (3) presence of at least one of the following features: convoluted nuclei; mitotic activity >or=3 x 10 HPF; and tumor necrosis. An algorithmic approach was devised for practical use in the diagnosis of this tumor.

Clinical characteristics of poorly differentiated thyroid carcinomas compared with those of classical papillary thyroid carcinomas

OBJECTIVE

The aim of this study was to compare the clinical presentation and prognosis of poorly differentiated thyroid carcinoma (PDTC) with those of classical papillary thyroid carcinoma (PTC) to identify the appropriate surgical modalities for use in conjunction with radioactive iodide ((131)I) therapy and external radiotherapy for treating PDTC.

DESIGN

Sixty-seven PDTC patients (mean age 50.3 +/- 18.1 years, range 14-82 years) underwent surgery at the Chang Gung Medical Centre (CGMC), Linkou. To compare clinical presentations and treatment outcomes, 134 age- and gender-matched patients with classical PTC were selected randomly from the patient database at CGMC.

RESULTS

Of the 67 PDTC patients, 53 underwent near-total thyroidectomy. Following surgery, 45 were administered (131)I for remnant ablation and treatment of distant metastatic disease. Forty-one of the 67 (61.2%) patients with PDTC and 26/134 (19.4%) with classical PTC failed to achieve disease-free status. Twenty-four of the 67 (34.3%) PDTC patients eventually died of thyroid cancer after a mean follow-up of 5.9 +/- 0.6 years. Age and TNM staging at surgery were significant indicators of PDTC patient survival and mortality.

CONCLUSIONS

As the prognosis for PDTC patients is poorer than that for classical PTC patients, (131)I treatment following surgery is useful. To improve the survival rate, early diagnosis is crucial for PDTC.

Prognostic factors of recurrence in encapsulated Hurthle cell carcinoma of the thyroid gland: a clinicopathologic study of 50 cases

BACKGROUND

Follicular carcinomas of the thyroid gland, including its oncocytic variant (so-called Hurthle cell carcinoma), are subdivided into the indolent encapsulated ("minimally invasive") and the clinically aggressive widely invasive tumors. There are, however, cases of encapsulated follicular carcinoma that recur and metastasize. Identifying these cases at the time of diagnosis is crucial for prognostic and therapeutic considerations. Because to the authors' knowledge most studies do not focus exclusively on the encapsulated Hurthle cell carcinoma (EHC), the current study attempted to identify predictors of recurrence in EHC.

METHODS

A tumor was defined as EHC if it was encapsulated, macroscopically well defined with microscopic but no macroscopic evidence of vascular or capsular invasion, and composed of > 75% follicular oncocytic cells. Retrospective chart review and microscopic examination identified 50 primary tumors meeting the above criteria at the Memorial Sloan-Kettering Cancer Center between 1967 and 2005. The cases were analyzed for various histologic and clinical parameters. Each parameter was correlated with recurrence-free survival (RFS).

RESULTS

Seven of 50 (14%) patients developed disease recurrence. All patients who developed recurrence were found to have a high number of foci of vascular invasion (> or = 4). In univariate analysis, > or = 4 foci of vascular invasion (P <.0001), tumor size > 4 cm (P = .049), the presence of mitosis (P = .018), and a solid/trabecular growth pattern (P = .009) were found to be correlated with a decreased RFS. Extensive capsular invasion, gender, and age did not confer a statistically higher recurrence rate. The finding of a solid/trabecular growth and mitosis correlated with the presence of numerous foci (> or = 4) of vascular invasion (P = .01 and P = .005, respectively).

CONCLUSIONS

A diligent search for vascular invasion is recommended in EHC that display mitosis or a solid/trabecular growth pattern. The presence of > or = 4 foci of vascular invasion should alert the pathologist and the clinician to a significantly higher risk of recurrence in EHC.

How to define follicular thyroid carcinoma?

The appropriate diagnosis of follicular thyroid carcinoma (FTC) still depends on its histological discrimination from follicular adenoma (including the distinction of benign from malignant oncocytic variants), papillary thyroid carcinoma (particularly from the follicular variants) and poorly differentiated thyroid carcinoma. The use of immunohistochemical markers contributed only marginally to better defining FTC. The introduction of the micro array technique, however, may offer the possibility of getting a better insight into the natural history, as well as predicting the clinical course, of a given thyroid nodule. This review attempts to recapitulate common standards in the diagnosis of FTC, to summarise current molecular data available to distinguish FTC from other benign and malignant tumours and, finally, to outline future perspectives to define FTC on its specific genetic features.

The C allele of theGNB3 C825T polymorphism of the G protein β3-subunit is associated with an increased risk for the development of oncocytic thyroid tumours

Carriers of the C allele of the common C825T polymorphism in the GNB3 gene of the G protein have been associated with the development of follicular thyroid adenomas. Since the C allele of this polymorphism is related to a lower signalling capacity, it was speculated whether the C825T polymorphism may play a particular role in oncocytic thyroid tumours, which are recognized for their reduced ability to synthesize thyroid-specific proteins and hormones, although they possess an intact thyroid-stimulating hormone receptor-adenylyl cyclase system. Using pyrosequencing, both the genotype distribution and the allele frequency of the C825T polymorphism were investigated in a series of 104 patients with oncocytic thyroid tumours of follicular cell origin [58 adenomas, 41 follicular thyroid carcinomas (FTCs), and five papillary thyroid carcinomas (PTCs)]; the results were compared with those obtained from 321 age and gender-matched healthy blood donors and a series of 327 non-oncocytic thyroid tumours of follicular cell origin (119 adenomas, 80 FTCs, and 186 PTCs). Analysis of the genotype distribution (comparing oncocytic with non-oncocytic tumours of the present series) revealed a significantly increased odds ratio (OR) for CC versus TT (OR = 4.22; p = 0.011) and CC versus CT (OR = 1.62; p = 0.049) carriers to develop an oncocytic thyroid tumour; ORs to develop an oncocytic thyroid tumour were also increased comparing the genotype distribution between the group of oncocytic tumours and healthy controls for CC versus TT (OR = 3.73; p = 0.017) and CC versus all T carriers (OR = 1.56; p = 0.034). Oncocytic thyroid tumours as a group showed a statistically significant increase of the C-allele frequency when compared with all non-oncocytic tumours (p = 0.0039) as well as healthy blood donors (p = 0.017). The results strongly suggest that the C allele of the GNB3 C825T polymorphism of the G protein beta3-subunit is associated with an increased risk for the development of oncocytic thyroid tumours. This polymorphism may thus be considered a (co)factor favouring the development of oncocytic thyroid tumours, although the biological mechanism(s) underlying this association remain obscure.

Poorly differentiated carcinomas of the thyroid with trabecular, insular, and solid patterns: a clinicopathologic study of 183 patients

BACKGROUND

The term poorly differentiated (PD) carcinoma was proposed 20 years ago to define aggressive, follicular-derived thyroid carcinomas with behavior intermediate between follicular/papillary and anaplastic carcinomas. Among the variable histologic patterns recognized in such tumors, trabecular-insular-solid (TIS) areas usually are predominant. Conversely, some authors pointed out that PD carcinomas are characterized by unequivocal, high-grade histology with atypias, high mitotic counts, and necrosis rather than by a specific growth pattern.

METHODS

The clinicopathologic features of a series of 183 thyroid carcinomas with predominant (n = 165 tumors) or focal (n = 18 tumors) TIS growth patterns were studied by univariate and multivariate overall survival analyses and were compared with clinical outcomes. Subgroups included tumors with predominant oxyphilic features (n = 66 tumors) and (residual) papillary carcinoma features (n = 24 tumors). Control groups of papillary (n = 68 tumors), follicular (n = 71 tumors), and anaplastic (n = 35 tumors) carcinomas also were included for overall survival analysis.

RESULTS

TIS carcinomas had an intermediate behavior between papillary/follicular and anaplastic carcinomas (P < 0.0001). Univariate and multivariate statistical analyses demonstrated that age > 45 years (P = 0.007), the presence of necrosis (P < 0.0001), and a mitotic count > 3 per 10 high-power fields (P = 0.01) were associated with poor outcome. A simplified scoring system based on statistically significant parameters allowed the identification of three prognostic subgroups (P < 0.0001).

CONCLUSIONS

PD TIS carcinomas overall followed a more aggressive course compared with differentiated thyroid carcinomas, irrespective of the extent of the TIS component. However, a numeric scoring system applied to specific clinicopathologic parameters further may identify three prognostic categories of patients who have significantly different survival rates at 5 years and 10 years.

RET rearrangements in archival oxyphilic thyroid tumors: New insights in tumorigenesis and classification of Hürthle cell carcinomas?

BACKGROUND

Oncocytic carcinomas (Hürthle cell carcinomas [HCCs]) are commonly considered a subgroup of follicular thyroid carcinomas (FTCs). Recent characterization of a subgroup of "Hürthle cell" papillary thyroid carcinomas (PTCs) was based on the identification of PTC-specific RET hybrid oncogenes in HCCs.

METHODS

We examined 27 HCCs, 4 oxyphilic FTCs, 5 oxyphilic PTCs, 2 poorly differentiated carcinomas arising from HCCs (HCC-UTCs), and 16 oxyphilic adenomas. Total RNA was extracted from paraffin-embedded thyroid neoplasms by a novel macrodissection technique that uses a cylindric punch. After reverse transcription-polymerase chain reaction-based screening for RET rearrangements, the samples were tested for all known RET/PTC 1 to 11 hybrids with the use of artificially constructed chimeric sequences as controls.

RESULTS

The elimination of C cells by punching dissection significantly reduced RET wild-type expression. RET hybrid oncogenes (7x RET/PTC1, 1x RET/PTC1L, 2x RET/PTC3, 5 uncharacterized RET/PTCx) were demonstrated in 7 of 27 HCCs, in 0 of 4 oxyphilic FTCs, in 4 of 5 oxyphilic PTCs, in 1 of 2 HCC-UTCs, and in 3 of 16 oxyphilic adenomas.

CONCLUSION

Our results suggest that the expression of rearranged RET hybrid oncogenes (1) is present in a similar percentage of HCCs when compared with the literature on nonoxyphilic PTCs, (2) defines PTC-like HCCs better than histomorphologic characterization, (3) excludes HCCs as a subgroup of FTCs, and (4) may play a role in the early tumorigenesis of oncocytic tumors.

Thyroid carcinomas with distant metastases: a review of 111 cases with emphasis on the prognostic significance of an insular component

Distant metastases (DM) are rare in well-differentiated thyroid carcinomas and correlate with a poor survival. Among the histologic subtypes, insular carcinoma has an intermediate prognosis that lies between well and undifferentiated carcinomas. To assess the characteristics that could predict a worse prognosis, we reviewed the initial thyroid cancer slides from patients with DM. We achieved a comparative statistical analysis with a control group without DM. Among 1230 differentiated carcinomas treated from 1960 to 1999, 9% developed DM. In this group the mean age was 53 years, with a 73% rate of death. The histologic slides were available in 80 cases. The primary thyroid tumors were classified as papillary (51 cases), follicular (25), and pure insular carcinomas (4). Extrathyroidal extension was present in 47% of papillary carcinomas. The mean tumor size was above 5 cm for all the histologic subtypes, and at least a vascular invasion was found in 69%. Fifty-four percent of these tumors had an insular component compared with only 6.5% in the control group. The statistical analysis confirmed by univariate and multivariate logistic regression that the risk of DM was highly elevated in the presence of insular carcinoma. Our study indicates that elevated age, large tumor size, vascular invasion, and extrathyroidal extension are important prognostic factors in well-differentiated carcinomas. We also demonstrate that the presence of an insular component in an otherwise differentiated carcinoma is a strong independent poor prognostic factor.

Poorly differentiated carcinomas of the thyroid gland: a review of the clinicopathologic features of a series of 28 cases of a heterogeneous, clinically aggressive group of thyroid tumors

We evaluated the clinicopathologic, immunohistochemical, lectin histochemical, ultrastructural and morphometric characteristics of a series of 28 poorly differentiated carcinomas of the thyroid (PDCT). The 28 tumors were classified according to their predominant growth pattern as insular (n=12), trabecular (n=10) and solid subtypes (n=6). The overall mortality rate was 46%. No significant differences were found among the 3 subtypes. Data obtained by lectin histochemistry, electron microscopy, and morphometry point to a closer relationship of PDCT to follicular than to papillary carcinoma. Our results do not support the subdivision of PDCT into subtypes.

Diagnosis of "follicular neoplasm": a gray zone in thyroid fine-needle aspiration cytology

The thyroid fine-needle aspiration (FNA) diagnosis of "follicular neoplasm" does not differentiate between a benign and malignant tumor. Often cases diagnosed as "follicular or Hürthle-cell neoplasm" undergo surgical excision for further characterization. The aim of this study was to identify clinical features that may help in predicting malignancy in patients with an FNA diagnosis of follicular neoplasm. One hundred eighty-four cases in 167 patients were diagnosed as "follicular neoplasm" among 1,024 thyroid FNA evaluated with on-site interpretation from 1998-2000. The cases were evaluated for the following variables: histologic diagnosis, age, sex, and size of the nodule. One hundred thirty-nine patients were female, and 28 were male (age range, 23-80 yr). Among 122 patients (67%) undergoing surgical excision (lobectomy, 96; total thyroidectomy, 26), malignancy was identified in 37 cases (31%). Nonpapillary (follicular/Hürthle) carcinoma was diagnosed in 11 (9%), follicular variant of papillary carcinoma in 25, and medullary carcinoma in 1 case. The risk of malignancy was greater in males (47% vs. 29%, P < 0.0004) than females, in nodules measuring 3 cm or more (55% vs. 23%, P < 0.0001), than in nodules measuring less than 3 cm, and in patients 40 or more yr old (20% vs. 10%, P = 0.0001) than in patients younger than 40 years. The diagnosis "follicular neoplasm" is indeterminate, and the majority of cases (70% in the current study) are benign. However, clinical features, including gender, nodule size, and age, can be a part of the decision analysis in selecting patients for surgery.

Clinical significance of molecular expression profiles of Hürthle cell tumors of the thyroid gland analyzed via tissue microarrays

Hürthle cell tumors are rare thyroid neoplasms for which disease biology is poorly understood and diagnosis of carcinoma can be challenging. The aim of the study was to characterize molecular expression profiles of Hürthle cell tumors and to determine the clinical significance of identified phenotypes. Paraffin-embedded tissue cores of normal thyroid (n = 18), and histopathologically well-defined Hürthle cell adenomas (n = 27), Hürthle cell tumors of unknown malignant behavior (n = 7), and minimally (n = 14) and widely (n = 21) invasive Hürthle cell carcinomas were arrayed in triplicate on tissue microarrays. Expression profiles of p53, mdm-2, p21, Bcl-2, cyclin D1, and Ki-67 were detected by immunohistochemistry and correlated with clinicopathological data and patient outcome using standard statistical methodology. Median follow-up time was 8 years. High Ki-67 proliferative index was evident only in the clinically aggressive widely invasive Hürthle cell carcinomas and was associated with significantly reduced relapse-free (P = 0.001) and disease-specific (P < 0.001) survival. The molecular phenotype of Hürthle cell tumors, independent of histopathological subtype diagnosis, was characterized by p53(-), mdm-2(+), p21(+/-), cyclin D1(-), and Bcl-2(+/-). Normal thyroid tissue demonstrated a p53(-), mdm-2(-), p21(-), cyclin D1(-), and Bcl-2(+) phenotype. The Bcl-2(+) phenotype was associated with improved relapse-free survival (P = 0.04) and disease-specific survival (P = 0.01) in widely invasive carcinomas and the Ki-67(+)/Bcl-2(-) phenotype was associated with the diagnosis of widely invasive Hürthle cell carcinoma (P < 0.001). This study demonstrates that tissue microarray-based profiling allows identification of molecular markers that are associated with patient prognosis. High Ki-67 proliferative index was associated with adverse outcome in Hürthle cell neoplasms. Together with down-regulation of Bcl-2, high Ki-67 proliferative index may be useful for diagnosing widely invasive Hürthle cell carcinomas. Molecular alterations in the p53 pathway play a role in Hürthle cell tumorigenesis, but other unidentified molecular changes seem to be required to induce the malignant phenotype.

Extensive DNA fragmentation in oxyphilic cell lesions of the thyroid

The in situ end-labeling (ISEL) method demonstrates DNA fragmentation, commonly regarded as a marker of apoptosis. We investigated by the ISEL procedure a series of 52 thyroid lesions, including 24 lesions of mitochondrion-rich oxyphilic cells, both benign and malignant, and 28 non-oxyphilic control tumors. A high percentage of nuclear ISEL staining (approximating to 100% in most cases) was observed in the vast majority of oxyphilic cells from both adenomas and carcinomas, in the absence of morphological apoptotic changes and with no immunocytochemical evidence of caspase activation. This pattern of DNA fragmentation was not observed in non-oxyphilic lesions and was confirmed in total extracted DNA. Moreover, a peculiar cytoplasmic staining was also observed in oxyphilic cells from both benign and malignant lesions, probably related to abnormal fragmentation of mitochondrial DNA. Similar staining patterns were detected in oxyphilic cell tumors of other organs (parathyroids, salivary glands, and kidneys). These findings are consistent with an extensive DNA fragmentation peculiar to oxyphilic cells, which is not directly related to apoptosis and whose origin and biological significance are presently unknown.

Analysis of Hurthle cell neoplasms of the thyroid by interphase fluorescence in situ hybridization

Recent studies have indicated that numerical chromosomal abnormalities including changes in p53 and cyclin D1 may be involved in Hurthle cell tumorigenesis. We analyzed a series of Hurthle cell neoplasms of the thyroid to evaluate the diagnostic and prognostic utility of numerical anomalies by DNA fluorescent probes for cyclin D1 and p53 gene loci and chromosomes 5, 7, 11, 12, 17, and 22. Interphase fluorescence in situ hybridization (FISH) analysis was performed on paraffin-embedded tissue sections from 10 Hurthle cell adenomas, 19 Hurthle cell carcinomas, and 7 normal thyroid tissues used as controls. Directly labeled fluorescent DNA probes for the centromere region of chromosomes 7, 11, 12, and 17 and locus-specific probes for chromosomes 5 and 22, cyclin D1, and p53 were utilized for dual-probe hybridizations. Sixty percent (6 of 10) Hurthle cell adenomas and 63% (12 of 19) Hurthle cell carcinomas showed chromosome gains. Twenty percent (2 of 10) Hurthle cell adenomas and 26% (5 of 19) Hurthle cell carcinomas showed chromosome losses. Normal thyroid tissues used as controls showed no chromosomal abnormalities. Among Hurthle cell tumors with chromosomal abnormalities, adenomas averaged 2.7 gains and 0.3 losses per case, and carcinomas averaged 3.3 gains and 0.6 losses per case. The two adenomas with chromosome losses each showed loss of one chromosome, whereas the five carcinomas with losses averaged 1.8 losses per case. Chromosome 22 was the most common loss identified, occurring in three of the 11 patients who died of disease. These results indicate that chromosomal imbalances as gains are common in both benign and malignant Hurthle cell neoplasms, but Hurthle cell carcinomas tend to have more chromosome losses than adenomas. Among Hurthle cell carcinomas in this study, chromosome losses were identified only from patients who died of disease. The loss of chromosome 22 may have prognostic value in Hurthle cell carcinoma of the thyroid.

Thyroid cytology and histology

Fine needle aspiration (FNA) is an economical procedure that allows prompt evaluation of a thyroidal mass. Careful attention to each step of the aspiration will allow good specimens to be obtained. The cytopathologist should obtain the aspirates or else should accompany the clinician performing the aspirations. Unsatisfactory specimens should constitute less than 5% of the total. Reliable diagnoses can be made of papillary carcinoma, medullary carcinoma, anaplastic carcinoma, chronic lymphocytic thyroiditis, benign cystic lesions and the usual colloid-rich adenomatoid nodules. The diagnosis of follicular neoplasms and some cellular adenomatoid nodules remains problematical. Therefore, some thyroid operations inevitably yield benign follicular lesions.

Management of undifferentiated thyroid cancer

Management of thyroid carcinoma relies upon the tumour cells maintaining the differentiated functions that are typical of normal thyroid follicular cells, such as: dependence upon thyrotropin for growth, production of thyroglobulin and effective transport of iodine. Likewise, differentiated thyroid carcinomas often exhibit an auspicious clinical behaviour with a slow rate of growth and low potential for invasion and distant metastasis. These features permit therapy of disseminated tumour, effective follow-up surveillance and the assumption of a good prognosis. As each of these features are lost, the opportunities for both disease status assessment and therapeutic intervention diminish accordingly. A major obstacle is our failure to define effective systemic treatments to replace radioiodine therapy, whose loss is consonant with the loss of iodine transport and retention. The extreme of undifferentiated clinical behaviour is epitomized by anaplastic thyroid carcinoma, a rare, terminally dedifferentiated malignancy that is rapidly and invariably fatal. It is important to be attuned to clinical clues suggesting the presence of dedifferentiated tumour and related prognostic signs. This allows the application of currently limited therapeutic options and defines the need for research to develop new systemic treatments.

Bcl-2 Gene Family in Endocrine Pathology: A Review

BcI-2 is a member of a large multigene family, which includes genes that can inhibit or promote apoptosis. The regulation of apoptosis is achieved by homo- or heterodimerization of their proteins through four highly conserved domains. Bcl-2 protein is a strong cell death suppressor in a wide range of cell types and under a variety of stimuli. Bcl-2 and the other members of this family are differentially expressed in the endocrine glands and disregulation of their expression seems to contribute to the neoplastic transformation in these organs. The significance of bcl-2 and the related proteins for endocrine pathology at the experimental and clinical level is reviewed in this article.

Downregulation of p27KIP1 and Ki67/Mib1 labeling index support the classification of thyroid carcinoma into prognostically relevant categories

The cyclin-dependent kinase inhibitor p27KIP1 has been proposed as a valuable prognostic indicator for a variety of human neoplasms. Immunohistochemical reactivity for p27KIP1 and the proliferation marker Ki67/Mib1 were investigated in 90 thyroid carcinomas of follicular cell origin. The neoplasms were divided into three prognostic groups on the basis of their morphologic features: group 1, well-differentiated papillary or follicular carcinomas with favorable pathologic features (43 papillary carcinomas and 4 minimally invasive follicular carcinomas); group 2, papillary or follicular carcinomas with unfavorable pathologic features (21 poorly differentiated carcinomas and 2 papillary carcinomas, tall cell variant); and group 3, undifferentiated, or anaplastic, carcinomas. p27KIP1 expression (p = 0.007) and Ki67/Mib1 labeling index (p = 0.02) showed a strong correlation with the subdivision of the thyroid carcinomas in the three prognostic groups with a significant linear trend for tumors with low p27KIP1 (p = 0.002) and high Ki67/Mib1 labeling index (p = 0.005) to segregate into the unfavorable categories (groups 2 and 3). Low p27KIP1 expression, but not cellular proliferation, was related to adverse prognostic factors, such as large tumor size (p = 0.03) and extrathyroidal extension (p = 0.01), but the correlation was not independent of the subdivision in the three groups. Low p27KIP1 expression (p = 0.03) and high proliferative rate (p = 0.02) were associated with poor survival, reflecting the close association between patient morbidity and mortality rates and tumor differentiation. No significant association could be seen between p27KIP1 or cellular proliferation and clinicopathologic parameters (e.g., age, sex, tumor size, extrathyroidal extension, vascular invasion, lymph node metastases, distant metastases, tumor stage, and survival rate) within any of the groups, or the histologic diagnosis of papillary versus follicular carcinoma irrespective of their degree of differentiation. Modulation of p27KIP1 and cellular proliferation patterns in thyroid carcinoma correlate with tumor differentiation and support the morphologic classification of thyroid carcinoma into prognostically relevant categories.

Proliferative activity of oxyphilic (Hurthle) cells in reactive and neoplastic thyroid lersions

The proliferative potential of oxyphilic (Hurthle) cells (HCs) present in neoplastic and non-neoplastic thyroid lesions is uncertain. To estimate the HCs ability to proliferate and to determine whether their proliferative activity correlates with the biologic behavior of different thyroid oxyphilic lesions, we selected 31 cases of chronic lymphocytic (Hashimoto's) thyroiditis and 28 oxyphilic (Hurthle cell) thyroid tumors, including 12 adenomas and 16 carcinomas. Seven histologically normal thyroid specimens from euthyroid patients served as control tissue. The proliferative activity of HCs was evaluated by means of a double immunostaining for Ki67 and a mitochondrial antigen (which specifically recognizes oxyphilic cells). Oxyphilic cells in thyroiditis had a low proliferative activity (PA: 0.55%), although higher than that of normal thyroid parenchyma (PA: 0.06%). Neoplastic HC lesions had a mean proliferative activity of 1.56% and 6.26% in adenomas and carcinomas, respectively. A statistically significant difference was observed between proliferative activity of non-neoplastic and neoplastic lesions (p<0.01), but not within the tumor group, between adenomas and carcinomas. In addition, HC carcinomas had a statistically significant positive correlation between proliferative activity and tumor size (p<0.01) and the presence of necrosis (p<0.001).

Oncocytic (Hürthle cell) tumors of the thyroid: distinct growth patterns comparedẁith clinicopathological features

Neoplastic growth results from cell production that exceeds cell loss. We registered mitotic and apoptotic indices (MI and AI) in 97 immunohistochemically verified oncocytic (Hürthle cell) tumors of the thyroid (OT; 50 adenomas [OA], 20 atypical adenomas [aOA], and 27 carcinomas [OC]) and compared these kinetic data with histological diagnoses and other parameters. MI, although very low in all, was significantly higher in carcinomas than in adenomas. Conversely, AI did not differ as much among the 3 groups. This indicates that the magnitude of cell deletion did not play a prominent role in determining the disparate growth of the 3 types of oncocytic tumors. Cluster analysis with MI and AI per case as variables revealed the existence of 3 groups of neoplasms with highly distinct growth characteristics: (1) near-steady state (n = 78, all diagnostic categories represented); (2) progressive (n = 9, mostly carcinomas); and (3) regressive (n = 10, mostly adenomas). MI distinguished between histologically benign and malignant with the greatest discriminant power of the variables tested. Proliferative indices should thus be included in the differential diagnostic evaluation of oncocytic thyroid tumors. Our study also suggests that invasiveness and growth are 2 diverging properties of carcinomas.

Diagnosis of malignant epithelial thyroid lesions: fine needle aspiration and histopathologic correlation

Fine needle aspiration is a diagnostic tool useful as a guide to patient management. We believe that its role in solving the diagnostic dilemmas presented by thyroid nodules is still underappreciated. Current fiscal constraints in health care might bring about a wider use of this simple technique to select patients for surgery. Care in sampling a mass is essential to obtain aspirates that are representative of the lesion and adequate in quantity for interpretation. Several aspirates are needed from all but the smallest masses. Most thyroid carcinomas are well-differentiated with a low grade of malignancy. The majority of these are papillary carcinomas, which are easily diagnosed in good cytologic smears. With fine needle aspirates the goal is to diagnose a follicular neoplasm and to separate it from the adenomatoid nodule. The follicular neoplasm then can be classified as adenoma or carcinoma with the histologic sections. The minimally invasive carcinoma still can be challenging to recognize. We hope that the cytologic criteria and histopathologic correlations presented here will help general pathologists who interpret aspirates. We believe that in the near future additional immunohistochemical methods and genetic markers will be used increasingly to discriminate among the neoplasms and to provide prognostic information.

Follicular and Hurthle cell carcinomas of the thyroid: a comparative study

University of Texas M. D. Anderson Cancer Center cases filed as Hurthle cell and follicular carcinoma were reviewed. Requirements for including a case in the study were that the diagnosis of Hurthle cell or follicular carcinoma be confirmed, that histologic material and clinical information be adequate, and that there be at least 9 years of follow-up. The study group included 18 cases of Hurthle cell carcinoma and 33 cases of follicular carcinoma. Ten of the Hurthle cell carcinomas had extrathyroid invasion, three had intrathyroid invasion, and five were encapsulated (i.e., they had intracapsular invasion only). In the follicular carcinoma group, 5 tumors had extrathyroid invasion, 14 had intrathyroid invasion, and 14 were encapsulated. When the cases were stratified according to extent of invasion in this manner, there was no statistically significant difference in rate of local recurrence, rate of metastasis (either regional lymph node or distant), or patient survival between Hurthle cell carcinoma and follicular carcinoma. Other variables including patient age and sex, treatment differences, tumor size, vascular invasion, predominant growth pattern (follicular versus solid-trabecular), nuclear size and pleomorphism, mitotic rate, and tumor necrosis did not provide significant additional prognostic information. Metastases of both Hurthle cell and follicular carcinoma were mostly distant and predominantly involved bone and lung. Behavioral differences between Hurthle cell and follicular carcinoma that were not statistically significant included a higher rate of local recurrence in Hurthle cell carcinoma with intrathyroid invasion, more frequent occurrence of regional lymph node metastasis in Hurthle cell carcinoma with extrathyroid invasion, and absence of distant metastasis and death caused by tumor in encapsulated Hurthle cell carcinoma. Five follicular carcinomas and one Hurthle cell carcinoma appeared to have arisen within an adenoma.

Immunohistochemical analysis of thyroid adenomas with Hurthle cells

Twenty-five cases of thyroid adenomas with Hurthle cell changes, both pure and focal, were studied histologically and immunohistochemically with two objectives: first to elucidate the relationship between the normal uninvolved thyroid and the adenoma; and second, to evaluate the role of immunohistochemical studies in adenomas with Hurthle cell changes. Representative sections were stained with a panel of nine antibodies directed against thyroglobulin (TG), high molecular weight keratin (HMK), low molecular weight keratin (LMK), p53, bcl-2, epithelial membrane antigen (EMA), S100, carcinoembryonic antigen (CEA) and HMB45. In all cases, uniform strong positive staining (+3) with TG and bcl-2 was seen in the normal thyroid tissue while the adenoma stained moderately positive (+2). The reverse pattern was observed with LMK staining. Non-adenomatous thyroid cells were p53-negative, the majority of the Hurthle cells, however, were p53-positive and adenomas with an increased number of Hurthle cells had an increased percentage of p53 staining. The expression of EMA was variable. All thyroid cells both outside and within the adenoma were S100-, CEA-4 and HMB45-negative in all cases. The exact significance of p53 overexpression in the Hurthle cells needs further evaluation.