Cytologic features of differentiated high-grade thyroid carcinoma: A multi-institutional study of 40 cases

BACKGROUND

Differentiated high-grade thyroid carcinoma (DHGTC) is recently recognized by the World Health Organization (WHO) as a subgroup of thyroid carcinomas with high-grade features while retaining the architectural and/or cytologic features of well-differentiated follicular-cell-derived tumors. The cytomorphology of DHGTC is not well documented despite potential implications for patient triage and management.

METHODS

The pathology archives of six institutions were searched for cases diagnosed on resection as "high-grade thyroid carcinoma" using WHO criteria. The fine-needle aspiration (FNA) cohort represents a 10-year period (2013-2023); all were reviewed to confirm DHGTC classification. The corresponding FNAs were assessed for 32 cytomorphologic features.

RESULTS

Forty cases of DHGTC with prior FNA were identified. The mean patient age was 64.2 years. The average lesion size was 4.9 cm, and the majority demonstrated a TI-RADS score of 4 or 5 (95.2%). Three main high-grade subsets of DHGTC based on corresponding histology included papillary thyroid carcinoma (65%), follicular carcinoma (22.5%), and oncocytic carcinoma (12.5%). Over 97% of FNA cases were classified as Bethesda category IV or above. Approximately 25% of DHGTC showed cytologic features that included marked cytologic atypia, increased anisonucleosis, large oval nuclei, mitotic activity, or necrosis (p < .05); 68% of DHGTC cases were associated with high-risk molecular alterations. TERT mutations occurred in 41%, of which 89% of these were associated with a second mutation, usually RAS or BRAF p.V600E.

CONCLUSIONS

Cytology has a low sensitivity for DHGTC, although a subset of DHGTCs have cytologic features raising the possibility of a high-grade thyroid carcinoma. Other findings include high-risk molecular changes and clinicopathologic features such as older patient age and larger lesion size.

Prognosis of Poorly Differentiated Thyroid Carcinoma: A Systematic Review and Meta-Analysis

BACKGRUOUND

Poorly differentiated thyroid carcinoma (PDTC) accounts for a small portion of thyroid carcinomas but contributes to a significant proportion of thyroid carcinoma-associated deaths. The clinicopathological prognostic factors and clinical outcomes of PDTC remain unclear. We aimed to evaluate the clinical outcomes of patients with PDTC after curative treatment.

METHODS

A comprehensive search was performed up to September 2023. We included studies investigating treatment outcomes in patients with PDTC who underwent initial surgery. The 5-year disease-free survival (DFS) and overall survival (OS) were extracted. In this meta-analysis, the enrolled PDTC histological criteria included 3rd, 4th, and 5th World Health Organization (WHO) and Memorial Sloan Kettering Cancer Center (MSKCC) classification. A random-effects model was used for the pooled proportion analysis. Meta-regression analysis was conducted to evaluate the prognostic factors.

RESULTS

Twenty retrospective studies published between 2007 and 2023, including 1,294 patients, met all inclusion criteria. Studies that diagnosed PDTC based on various histological criteria including 3rd WHO (n=5), 4th WHO (n=12), 5th WHO (n=2), and MSKCC (n=1) were included. Overall, 5-year DFS and 5-year OS were 49.4% (95% confidence interval [CI], 42.3 to 56.4) and 73.8% (95% CI, 66.5 to 79.9), with moderate heterogeneity of 58% and 55%, respectively. In meta-regression analysis, extrathyroidal extension (ETE) was a prognostic factor for OS.

CONCLUSION

The meta-analysis of DFS and OS in patients with PDTC show the moderate heterogeneity with a variety of histological criteria. ETE appears to have a significant impact on OS, regardless of histological criteria.

Management of Poorly Differentiated Thyroid Cancer and Differentiated High-Grade Thyroid Carcinoma

Thyroid carcinoma of follicular cell origin exists on a histopathologic and clinical spectrum. The authors focus on the category of tumors that fall between the very favorable well-differentiated thyroid carcinomas and the very unfavorable anaplastic thyroid carcinomas. These intermediately aggressive tumors include poorly differentiated thyroid carcinoma and the newly defined differentiated high-grade thyroid carcinoma. Both diagnoses require certain histopathologic requirements be met in order to accurately identify these tumors post-operatively. Management remains primarily surgical though adjunctive treatments such as molecular targeted therapies (eg, tyrosine kinase inhibitors) and differentiation therapy (to restore tumor response to radioactive iodine) are also becoming available.

A Comprehensive Review and Insights into the New Entity of Differentiated High-Grade Thyroid Carcinoma

Differentiated high-grade thyroid carcinoma (DHGTC) is a new subset within the spectrum of thyroid malignancies. This review aims to provide a comprehensive overview of DHGTC, focusing on its historical perspective, diagnosis, clinical characteristics, molecular profiles, management, and prognosis. DHGTC demonstrates an intermediate prognosis that falls between well-differentiated thyroid carcinoma and anaplastic thyroid carcinoma. Previously unenumerated, this entity is now recognized for its significant impact. Patients with DHGTC often present at an older age with advanced disease and exhibit aggressive clinical behavior. Molecularly, DHGTC shares similarities with other thyroid malignancies, harboring driver mutations such as BRAFV600E and RAS, along with additional late mutations. The unique behavior and histologic features of DHGTC underscore the necessity of precise classification for prognostication and treatment selection. This highlights the critical importance of accurate diagnosis and recognition by pathologists to enrich future research on this entity further.

Poorly differentiated thyroid carcinoma: molecular, clinico-pathological hallmarks and therapeutic perspectives

Poorly differentiated thyroid carcinoma (PDTC) is a rare and extremely aggressive tumor, accounting for about 2-15% of all thyroid cancer. PDTC has a distinct biological behavior compared to well-differentiated and anaplastic thyroid carcinoma and, in last years, it has been classified as a separate entity from both anatomopathological and clinical points of view. Nevertheless, there is still a lack of consensus among clinicians regarding inclusion criteria and definition of PDTC that affects its diagnosis and clinical management. Due to its rarity and difficulty in classification compared to other tumors, very few studies are available to date and series often include different histotypes in addition to PDTC. This review focuses on main studies concerning PDTC summarizing the evolution in the definition of its diagnosis criteria, clinicopathological features, management, and outcome. The data available confirm that the pathological evaluation and classification of PDTC are crucial and should therefore be standardized. Since the clinical presentation and prognosis of PDTC may vary widely depending on the different stage of the disease at diagnosis, the patient's management may differ in treatment and should be tailored to each patient. Finally, this review discusses advances in molecular insights of PDTC that, together with the implementation of both in vitro and in vivo models, will provide valuable insights into biological mechanisms of progression, metastasis, and invasion of this aggressive thyroid carcinoma. Further studies on larger, carefully selected series are needed to better assess the peculiar features of PDTC and to better define its management by focusing on the best diagnostic and therapeutic approaches.

Low Mitotic Activity in Papillary Thyroid Cancer: A Marker for Aggressive Features and Recurrence

CONTEXT

The significance of low mitotic activity in papillary thyroid cancer (PTC) is largely undefined.

OBJECTIVE

We aimed to determine the behavioral landscape of PTC with low mitotic activity compared to that of no- and high-mitotic activity.

METHODS

A single-institution consecutive series of PTC patients from 2018-2022 was reviewed. Mitotic activity was defined as no mitoses, low (1-2 mitoses/2 mm2) or high (≥3 mitoses/2 mm2) per the World Health Organization. The 2015 American Thyroid Association risk stratification was applied to the cohort, and clinicopathologic features were compared between groups. For patients with ≥6 months follow-up, Cox regression analyses for recurrence were performed.

RESULTS

640 PTCs were included - 515 (80.5%) no mitotic activity, 110 (17.2%) low mitotic activity, and 15 (2.3%) high mitotic activity. Overall, low mitotic activity exhibited rates of clinicopathologic features including vascular invasion, gross extrathyroidal extension, and lymph node metastases in between those of no- and high-mitotic activity. PTCs with low mitotic activity had higher rates of intermediate- and high-risk ATA risk stratification compared to those with no mitotic activity (p < 0.001). Low mitotic activity PTCs also had higher recurrence rates (15.5% vs. 4.5%, p < 0.001). Low mitotic activity was associated with recurrence, independent of the ATA risk stratification (HR 2.96; 95% CI 1.28-6.87, p = 0.01).

CONCLUSIONS

Low mitotic activity is relatively common in PTC and its behavior lies within a spectrum between no- and high-mitotic activity. Given its association with aggressive clinicopathologic features and recurrence, low mitotic activity should be considered when risk stratifying PTC patients for recurrence.

Current evidences in poorly differentiated thyroid carcinoma: a systematic review and subsection meta-analysis for clinical decision making

BACKGROUND

Poorly differentiated thyroid carcinoma (PDTC) is a distinct entity with intermediate prognosis between indolent follicular thyroid cancers and anaplastic carcinoma. The management guidelines are not standardized for these cancers due its low prevalence and limited available literature. Therefore, we did this systematic review with emphasis on current evidence on diagnosis, imaging, molecular markers, and management of these carcinomas.

MATERIALS AND METHODS

We searched four databases, PubMed, Medline, EMBASE, and Emcare to identify studies published till October 2023. All studies reporting diagnostic tests, imaging, molecular marker expression and management of PDTC were included in the review. The meta-analysis was conducted on expression of molecular markers in these cancers following recommendations of the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA). Random-effects meta-analysis was used to calculate pooled estimated prevalence with 95% confidence intervals. Based on the inclusion criteria, 62 articles were selected to be incorporated for the review. Differences in pathological diagnostic criteria of PDTC was noted in literature which was addressed in WHO 2022 diagnostic terminologies with expansion of the definition. Surgical management is uniformly recommended for early stage PDTC. However, literature is divided and anecdotal for recommendations on radioactive iodine (RAI), extent of neck dissection and adjuvant treatment in PDTC. Evidence for Next Generation Sequencing (NGS), novel theragnostic approaches, immunotherapy targets are evolving. Based on the subset analysis for expression of molecular markers, we found the most common markers expressed were TERT (41%), BRAF (28%) and P 53 (25%).

CONCLUSION

Poorly differentiated thyroid carcinomas have a high case fatality rate (up to 31%). Eighty-five % of the patients who succumb to the disease have distant metastasis. Even though under-represented in literature, evidence-based management of these aggressive tumors can help personalize the treatment for optimal outcomes.

Prevalence of Differentiated High-Grade Thyroid Carcinoma Among Well-Differentiated Tumors: A Systematic Review and Meta-Analysis

Background: The current edition of the World Health Organization (WHO) classification of endocrine tumors introduced grading for follicular cell-derived thyroid cancer. Tumors with necrosis and/or high mitotic count but not fulfilling the Turin criteria for poorly differentiated carcinoma will be reclassified as differentiated high-grade thyroid carcinoma (DHGTC). However, the impact of this reclassification has not been evaluated. In this study, we performed a systematic review and meta-analysis to estimate the prevalence of this new entry across thyroid tumor subtypes. Methods: In this systematic review and meta-analysis, studies reporting data on necrosis and/or mitoses in well-differentiated thyroid carcinoma (WDTC) were used to estimate the prevalence of DHGTC. Heterogeneity and potential publication bias were also evaluated. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed, and quality assessment was performed using a modification of the Newcastle-Ottawa scale. The study has been registered in the International Prospective Register of Systematic Reviews (PROSPERO, ID: CRD42022378716). Results: In clinically unselected patients, the prevalence of DHGTC in WDTC was 0.072 [95% confidence interval, CI, = 0.045-0.113]. The proportion of high-grade tumors greatly varied across growth patterns and subtypes. Overall, the prevalence of DHGTC was higher in follicular thyroid carcinoma (FTC; 0.146 [CI = 0.101-0.205]) than in papillary thyroid carcinoma (PTC; 0.059 [CI = 0.036-0.097]). Diffuse sclerosing, follicular, and classic subtype PTC had the lowest rates of high-grade features (i.e., 0.018 [CI = 0.004-0.084]; 0.036 [CI = 0.010-0.124]; and 0.042 [CI = 0.027-0.066], respectively), while a greater proportion of solid trabecular and histologically aggressive PTC could be reclassified as DHGTC (i.e., 0.154 [CI = 0.067-0.314] and 0.168 [CI = 0.108-0.252], respectively). Similar proportions were obtained for minimally and widely invasive FTC (i.e., 0.136 [CI = 0.058-0.287] and 0.152 [CI = 0.086-0.254], respectively). Finally, in a cohort of patients with poor prognosis (i.e., fatal cases, metastatic and radioiodine resistant tumors, cases with biochemical recurrence), the proportion of DHGTC was 0.287 [CI = 0.155-0.469]. Conclusions: Following the current WHO indications, some tumors will be reclassified as DHGTC. The proportion of tumors with high-grade features is relevant in FTC, solid trabecular, and histologically aggressive PTC subtypes. A remarkable enrichment in DHGTC among patients with poor prognosis confirms the negative impact of high-grade features on outcome.

Incidence and Clinicopathological Features of Differentiated High-Grade Thyroid Carcinomas: An Institutional Experience

Differentiated high-grade thyroid carcinoma (DHGTC) is a new entity in the 2022 WHO classification. We aimed to investigate the incidence and clinicopathological features of differentiated HG thyroid carcinoma (DHGTC) and compare the clinicopathological parameters of DHGTC, DTC without HG features, and poorly differentiated thyroid carcinoma (PDTC). A total of 1069 DTCs including papillary thyroid carcinomas (PTCs) and follicular thyroid carcinomas (FTCs) were included in this study. Consecutive 22 PDTCs were also included for comparative purposes. There were a total of 14 (1.3%) cases of DHGTCs, with 13 HGPTCs (1.2% of PTCs) and one HGFTC (6.7% of FTCs). Compared to DTCs without HG features, DHGTCs were associated with larger tumor size, presence of blood vessel invasion, gross extrathyroidal extension, distant metastasis at the time of diagnosis, higher American Joint Committee on Cancer stage, high American Thyroid Association risk, and TERT promoter mutations. DHGTC and PDTC showed a significantly shorter recurrence-free survival (RFS) than DTC without HG features. Multivariate Cox regression analysis revealed that blood vessel invasion, lateral node metastasis, TERT promoter mutations, and HG features were independent prognostic factors (all p < 0.05). When tumor necrosis and increased mitotic count were evaluated separately, tumor necrosis, but not increased mitotic counts, was found to be an independent prognostic factor (p = 0.006). This study confirmed that DHGTC is significantly associated with aggressive clinicopathological features and poor clinical outcomes, similar to PDTC. Although the incidence is low, careful microscopic examination of HG features in DTC is required.

High Grade Differentiated Follicular Cell-Derived Thyroid Carcinoma Versus Poorly Differentiated Thyroid Carcinoma: A Clinicopathologic Analysis of 41 Cases

Criteria overlap for separating between malignant follicular epithelial cell-derived thyroid gland neoplasms with high grade features of increased mitoses and tumor necrosis but lacking anaplastic histology. Patterns of growth, nuclear features, tumor necrosis, and various mitotic index cutoffs are suggested, but a reproducible Ki-67-based labeling index has not been established. Forty-one cases diagnosed as poorly differentiated thyroid carcinoma (PDTC) or high grade differentiated follicular cell-derived thyroid carcinoma (HGDFCDTC) were reviewed, with histologic features, mitotic figure counts, and Ki-67 labeling index reviewed on cases within Southern California Permanente Medical Group from 2010 to 2021 to establish any potential outcome differences. There were 17 HGDFCDTC (nine papillary thyroid carcinoma; eight oncocytic follicular thyroid carcinoma), median age 64 years, affecting nine females and eight males. Tumors were large (median, 6.0 cm), usually unifocal (n = 13), with only one tumor lacking invasion. Tumor necrosis was present in all; median mitotic count was 5/2 mm² (median Ki-67 labeling index 8.3%). Three patients had metastatic disease at presentation, with additional metastases in four patients (41.2% developed metastases); 11 were without evidence of disease (median 21.2 months); with the remaining six patients alive (n = 4) or dead (n = 2) with metastatic disease (median 25.8 months). Criteria associated with an increased risk of developing metastatic disease: widely invasive tumors; age ≥ 55 years; male; advanced tumor size and stage; extrathyroidal extension; but not increased mitotic rate or higher labeling index. There were 24 PDTC, median age 57.5 years, affecting 13 females and 11 males. Tumors were large (median, 6.9 cm), with 50% part of multifocal disease, with three tumors lacking invasion. Insular/trabecular/solid architecture was seen in all tumors; tumor necrosis was present in 23; and median mitotic count was 6/2 mm² (median Ki-67 labeling index 6.9%). Five patients had metastatic disease at presentation, with additional metastases in 3 patients (29.2% developed metastases); 16 were without evidence of disease (median, 48.1 months); with the remaining 8 patients alive (n = 3) or dead (n = 5) with metastatic disease (median, 22.4 months). Criteria associated with an increased risk of developing metastatic disease: widely invasive tumors; male; advanced tumor size and stage; extrathyroidal extension; but not increased mitotic rate or higher labeling index. HGDFCDTC shows tumor necrosis, a median Ki-67 labeling index of 8.3%, with a high percentage (41%) of patients developing metastatic disease. Extent of invasion (non-invasive, minimally invasive, angioinvasive, widely invasive) correlates strongly with developing metastatic disease. PDTC presents at a slightly younger age, with large tumors, often in a background of multifocal tumors, with tumor necrosis nearly always seen, a median Ki-67 labeling index of 6.9%, with 29% of patients developing metastatic disease. Separation between groups is meaningful as early metastatic disease is relatively common, but mitotic counts/labeling indices are not different between the groups nor able to potentially risk stratify development of metastatic disease.

The 5th edition of WHO classification of tumors of endocrine organs: changes in the diagnosis of follicular-derived thyroid carcinoma

The 5^th edition of the World Health Organization (WHO) classification of endocrine tumors was released in 2022. Several novelties have been introduced concerning the nomenclature and histopathological diagnosis of follicular-derived thyroid neoplasms. Tumor types have been sharply classified according to prognostic risk categories into benign tumors, low-risk neoplasms and malignant neoplasms. A grading system for differentiated thyroid carcinomas has been implemented with the aim of improving the stratification of tumors. Particular attention has been paid to the molecular profile of well-differentiated histotypes. In this review, the main changes introduced by the latest edition of the WHO system are presented. The practical effects on the diagnostic pathology of thyroid tumors, along with the clinical implications expected with the new classification scheme, are critically 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.

Diagnostic, Prognostic, and Predictive Role of Ki67 Proliferative Index in Neuroendocrine and Endocrine Neoplasms: Past, Present, and Future

The introduction of Ki67 immunohistochemistry in the work-up of neuroendocrine neoplasms (NENs) has opened a new approach for their diagnosis and prognostic evaluation. Since the first demonstration of the prognostic role of Ki67 proliferative index in pancreatic NENs in 1996, several studies have been performed to explore its prognostic, diagnostic, and predictive role in other neuroendocrine and endocrine neoplasms. A large amount of information is now available and published results globally indicate that Ki67 proliferative index is useful to this scope, although some differences exist in relation to tumor site and type. In gut and pancreatic NENs, the Ki67 proliferative index has a well-documented and accepted diagnostic and prognostic role and its evaluation is mandatory in their diagnostic work-up. In the lung, the Ki67 index is recommended for the diagnosis of NENs on biopsy specimens, but its diagnostic role in surgical specimens still remains to be officially accepted, although its prognostic role is now well documented. In other organs, such as the pituitary, parathyroid, thyroid (follicular cell-derived neoplasms), and adrenal medulla, the Ki67 index does not play a diagnostic role and its prognostic value still remains a controversial issue. In medullary thyroid carcinoma, the Ki67 labelling index is used to define the tumor grade together with other morphological parameters, while in the adrenal cortical carcinoma, it is useful to select patients to treated with mitotane therapy. In the present review, the most important information on the diagnostic, prognostic, and predictive role of Ki67 proliferative index is presented discussing the current knowledge. In addition, technical issues related to the evaluation of Ki67 proliferative index and the future perspectives of the application of Ki67 immunostaining in endocrine and neuroendocrine neoplasms is discussed.

The 2022 WHO classification of thyroid tumors: novel concepts in nomenclature and grading

The fifth edition of the Classification of Endocrine and Neuroendocrine Tumors has been released by the World Health Organization. This timely publication integrates several changes to the nomenclature of non-neoplastic and neoplastic thyroid diseases, as well as novel concepts that are essential for patient management. The heterogeneous group of non-neoplastic and benign neoplastic lesions are now collectively termed as 'thyroid follicular nodular disease' to better reflect the clonal and non-clonal proliferations that clinically present as multinodular goiter. Thyroid neoplasms originating from follicular cells are distinctly divided into benign, low-risk and malignant neoplasms. The new classification scheme stresses that papillary thyroid carcinoma (PTC) should be subtyped based on histomorphologic features irrespective of tumor size to avoid treating all sub-centimeter/small lesions as low-risk disease. Formerly known as the cribriform-morular variant of PTC is redefined as cribriform-morular thyroid carcinoma since this tumor is now considered a distinct malignant thyroid neoplasm of uncertain histogenesis. The 'differentiated high-grade thyroid carcinoma' is a new diagnostic category including PTCs, follicular thyroid carcinomas and oncocytic carcinomas with high-grade features associated with poorer prognosis similar to the traditionally defined poorly differentiated thyroid carcinoma as per Turin criteria. In addition, squamous cell carcinoma of the thyroid is now considered a morphologic pattern/subtype of anaplastic thyroid carcinoma. In this review, we will highlight the key changes in the newly devised fifth edition of the WHO classification scheme of thyroid tumors with reflections on its applicability in patient management and future directions in this field.

Advances in Thyroid Pathology: High Grade Follicular Cell-derived Thyroid Carcinoma and Anaplastic Thyroid Carcinoma

In the upcoming World Health Organization fifth edition classification of endocrine tumors, there were several major changes related to high grade follicular-derived thyroid carcinoma (HGFCTC) and anaplastic thyroid carcinoma (ATC) based on emerging evidence about the diagnostic criteria clinical behavior, prognostic factors, and molecular signatures of these tumors. In this review, we aim to summarize the major evolutions of HGFCTC and ATC. HGFCTC is a nonanaplastic carcinoma with high grade features (High mitotic count, tumor necrosis). It is subdivided into poorly differentiated thyroid carcinoma diagnosed using the Turin proposal and differentiated high grade thyroid carcinoma. The latter is defined by the presence of the cytoarchitectutal features of well-differentiated thyroid carcinoma (eg, papillae) but harbors elevated mitotic activity and/or tumor necrosis. Poorly differentiated thyroid carcinoma is predominantly RAS -driven and associated with RAI avidity and high propensity for distant metastasis, whereas differentiated high grade thyroid carcinoma is mostly BRAFV600E -driven. ATC may show a wide range of histologic features. Carcinoma of pure squamous phenotype is associated with a high frequency of BRAF V600E mutations and is now considered as a subtype of ATC. There is a stepwise molecular progression from well-differentiated carcinoma to HGFCTC to ATC manifested by 1) early and persistent driver alteration in the MAPK pathway, particularly BRAF V600E and RAS mutations, and 2) gain of secondary aggressive molecular signatures (such as TERT promoter and TP53 mutations) when tumors progress from well-differentiated to high grade to anaplastic carcinoma.

Prognostic Utility of the Ki-67 Labeling Index in Follicular Thyroid Tumors: a 20-Year Experience from a Tertiary Thyroid Center

Follicular thyroid tumors pose a diagnostic challenge on the preoperative level, as the discrimination between follicular thyroid carcinoma (FTC) and adenoma (FTA) demands careful histopathological investigation. Moreover, prognostication of FTCs is mostly based on tumor size and extent of invasive properties, while immunohistochemical markers pinpointing high-risk cases are lacking. We have routinely established a Ki-67 labeling index for follicular thyroid tumors since 1999. To assess the potential value of Ki-67 as an adjunct tool to (1) correctly separate FTCs from FTAs and (2) help identify poor-prognosis FTCs, we collected histopathological and clinical data from 818 follicular thyroid tumors with a histological Ki-67 labeling index established in clinical routine practice (516 FTAs, 252 FTCs, and 50 follicular thyroid tumors of uncertain malignant potential (FT-UMPs)). The Ki-67 labeling index was higher in FTCs (mean 5.8%) than in FTAs (mean 2.6%) (P < 0.001), and a receiver operating characteristic curve analysis revealed a cut-off value of 4% to separate FTC from FTA with a sensitivity and specificity of 65% and 83%, respectively. Similarly, a Ki-67 labeling index above 4% was found to identify FTCs that later metastasized from clinically indolent FTCs with a sensitivity and specificity of 80% and 48%, respectively. Ki-67 constituted an independent predictor of future FTC metastases/recurrence and death of disease, and a value > 4% was a reliable prognostic marker within individual pT staging groups. We conclude that Ki-67 is a potentially valuable marker for the prognostication of FTCs, and future implementation in the histopathological assessments of follicular thyroid tumors could be beneficial if reproduced in international series.

Postoperative radioiodine therapy impact on survival in poorly differentiated thyroid carcinoma: a population-based study

PURPOSE

The true impact of postoperative radioiodine therapy on survival has been controversial for patients with poorly differentiated thyroid carcinoma (PDTC). We aimed to determine the impact of postoperative radioiodine on survival in PDTC through a population-based study.

METHODS

Data on patients with PDTC were collected from the US SEER database (2004 to 2015). Patients were divided into the radioiodine group and nonradioiodine group. Survival comparison between groups was evaluated by Kaplan-Meier curves, log-rank test and multivariate Cox regression analysis. Akaike information criterion was used to select variables in the nomogram. The performance of the nomogram was assessed by discrimination (C-index) and calibration plots.

RESULTS

The radioiodine group had more aggressive features, such as advanced tumor node metastasis stage and radical surgery, compared to the nonradioiodine group. PDTC patients receiving radioiodine therapy had a significant survival advantage in terms of overall survival (OS) (P = 0.001) but not in terms of cancer-specific survival (P = 0.083). Multivariate analysis revealed radioiodine therapy was an independent favorable factor for OS in PDTC patients (hazard ratio = 0.57; 95% CI, 0.44-0.75, P < 0.001). Subgroup analysis identified patients' characteristics favoring radioiodine therapy. The nomogram (age, tumor size, extension, neck lymph nodes metastasis and radioiodine therapy) of OS for predicting 3-, 5- and 10-year OS probability showed good discrimination (C-index, 0.797) and calibration power.

CONCLUSION

Postoperative radioiodine therapy can prolong the long-term OS in patients with PDTC, and is an independent favorable prognostic factor for those patients. Further prospective studies are warranted.

Development and validation of a nomogram model for cancer-specific survival of patients with poorly differentiated thyroid carcinoma: A SEER database analysis

BACKGROUND

This study aimed to establish and validate an accurate prognostic model, based on demographic and clinical parameters, for predicting the cancer-specific survival (CSS) of patients with poorly differentiated thyroid carcinoma (PDTC).

MATERIALS AND METHODS

Patients diagnosed with PDTC between 2004 to 2015 were obtained from the Surveillance, Epidemiology, and End Results (SEER) database. Randomly split the data into training and validation sets. Kaplan-Meier analysis with the log-rank test was performed to compare the survival distribution among cases. Univariate and multivariate Cox proportional hazards regression analyses were used to identify independent prognostic factors, which were subsequently utilized to construct a nomogram for predicting the 5- and 10-year cancer-specific survival of patients with PDTC. The discriminative ability and calibration of the nomogram model were assessed using the concordance index and calibration plots, respectively. In addition, we performed a decision curve analysis to assess the clinical value of the nomogram. Simultaneously, we compared the predictive performance of the nomogram model against that of the American Joint Committee on Cancer (AJCC) T-, N-, M-stage.

RESULTS

A total of 970 eligible patients were randomly assigned to either a training cohort (n = 679) or a validation cohort (n = 291). The Kaplan-Meier analysis revealed that there were no significant differences in cumulative survival based on the race, radiation, and marital status of patients. The stepwise Cox regression model showed that the model was optimal when the following five variables were included: age, tumor size, T-, N-, and M-stage. A nomogram was developed as a graphical representation of the model and exhibited good calibration and discriminative ability in the study. Compared to the T-, N-, and M-stage, the C-index of nomogram (training group: 0.807, validation group: 0.802), the areas under the receiver operating characteristic curve of the training set (5-year AUC: 0.843, 10-year AUC:0.834) and the validation set (5-year AUC:0.878, 10-year AUC:0.811), and the calibration plots of this model all exhibited better performance. At last, compared with T-, N-, and M-stage, the decision curve analysis indicated that the nomogram had excellent clinical net benefit.

CONCLUSIONS

The nomogram developed by us can accurately predict the CSS of PDTC patients. It can help clinicians determine appropriate treatment strategies for poorly differentiated thyroid carcinoma patients.

Primary high-grade non-anaplastic thyroid carcinoma: a retrospective study of 364 cases

AIMS

We aimed to study the clinicopathological and molecular features of high-grade non-anaplastic thyroid carcinomas (HGTCs), a carcinoma with a prognosis intermediate between those of well-differentiated carcinoma and anaplastic carcinoma.

METHODS AND RESULTS

This study included 364 HGTC patients: 200 patients (54.9%) were diagnosed with poorly differentiated thyroid carcinoma (PDTC), based on the Turin consensus (HGTC-PDTC), and 164 were diagnosed with high-grade features that did not meet the Turin criteria (HGTC-nonPDTC). HGTCs are aggressive: the 3-year, 5-year, 10-year and 20-year disease-specific survival (DSS) rates were 89%, 76%, 60%, and 35%, respectively. Although DSS was similar between HGTC-PDTC and HGTC-nonPDTC patients, HGTC-PDTC was associated with higher rate of radioactive iodine avidity, a higher frequency of RAS mutations, a lower frequency of BRAF V600E mutations and a higher propensity for distant metastasis (DM) than HGTC-nonPDTC. Independent clinicopathological markers of worse outcome were: older age, male sex, extensive necrosis and lack of encapsulation for DSS; older age, male sex and vascular invasion for DM-free survival; and older age, necrosis, positive margins and lymph node metastasis for locoregional recurrence-free survival. The frequencies of BRAF, RAS, TERT, TP53 and PTEN alterations were 28%, 40%, 55%, 11%, and 10%, respectively. TP53, PTEN and TERT were independent molecular markers associated with an unfavourable outcome, independently of clinicopathological parameters. The coexistence of BRAF V600E and TERT promoter mutation increased the risk of DM.

CONCLUSIONS

The above data support the classification of HGTC as a single group with two distinct subtypes based on tumour differentiation: HGTC-PDTC and HGTC-nonPDTC.

How to identify indolent thyroid tumors unlikely to recur and cause cancer death immediately after surgery-Risk stratification of papillary thyroid carcinoma in young patients

Current histopathological diagnosis methods cannot distinguish the two types of thyroid carcinoma: clinically significant carcinomas with a potential risk of recurrence, metastasis, and cancer death, and clinically insignificant carcinomas with a slow growth rate. Both thyroid tumors are diagnosed as "carcinoma" in current pathology practice. The clinician usually recommends surgery to the patient and the patient often accepts it because of cancer terminology. The treatment for these clinically insignificant carcinomas does not benefit the patient and negatively impacts society. The author proposed risk stratification of thyroid tumors using the growth rate (Ki-67 labeling index), which accurately differentiates four prognostically relevant risk groups based on the Ki-67 labeling index, ≥30%, ≥10 and <30%, >5 and <10%, and ≤5%. Indolent thyroid tumors with an excellent prognosis have the following four features: young age, early-stage (T1-2 M0), curatively treated, and low proliferation index (Ki-67 labeling index of ≤5%), and are unlikely to recur, metastasize, or cause cancer death. Accurate identification of these indolent tumors helps clinicians select more conservative treatments to avoid unnecessary aggressive (total thyroidectomy followed by radio-active iodine) treatments. Clinicians can alleviate the fears of patients by confirming these four features, including the low proliferation rate, in a pathology report immediately after surgery when patients are most concerned.

Papillary Thyroid Carcinoma with High-Grade Features Versus Poorly Differentiated Thyroid Carcinoma: An Analysis of Clinicopathologic and Molecular Features and Outcome

Background: Similar to poorly differentiated thyroid carcinoma (PDTC), papillary thyroid carcinoma with high-grade features (PTC HGF) demonstrates increased mitotic activity and/or necrosis; however, PTC HGF is excluded from the World Health Organization (WHO) definition of PDTC based on maintained nuclear features of PTC. Methods: Consecutive tumors that met criteria for PTC HGF, defined as tumors with maintained nuclear features of PTC and mitoses numbering 5 or more per 10 contiguous high-power fields and/or tumor necrosis, and PDTC (defined as per the WHO criteria) were identified. Clinicopathologic characteristics, follow-up data, and targeted next-generation sequencing results were compared between groups. Results: There were 15 PTC HGF and 47 PDTC. PTC HGF was associated with a higher rate of pT4 disease (53% vs. 13%, p = 0.0027) and lymph node metastases (73% vs. 38%, p = 0.049). The disease-specific survival was worse for patients with PTC HGF compared with those with PDTC using Kaplan-Meier estimation (p < 0.001) and was worse in subgroup analysis evaluating patients with widely invasive PDTC (i.e., those with a similar rate of pT4 disease) and PTC HGF (p = 0.040). PTC HGF had a higher BRAF^V600E mutation rate (42% vs. 3%; p = 0.003), a trend toward more gene fusions (25% vs. 3%; p = 0.052), and a higher rate of relative gain of 1q (67% vs. 15%; p = 0.002) than PDTC. Conclusions: Our results demonstrate that PTC HGF are important to recognize based on their aggressive behavior. The molecular differences between PTC HGF and PDTC suggest that PTC HGF should be considered a distinct group from PDTC.

Solid variant of papillary thyroid carcinoma: An analysis of 28 cases with current literature

INTRODUCTION

Solid variant papillary thyroid cancer (SVPTC) is a rare variant of papillary thyroid carcinoma (PTC) and its prognostic value is still unclear. Therefore, we re-evaluate the histopathological and clinicopathological features of 28 patients with SVPTC in the light of current literature.

MATERIAL-METHODS

Of the 1308 cases were previously diagnosed with PTC and 28 (2,1%) of them which had been diagnosed with SVPTC were re-evaluated retrospectively.

RESULTS

Of the 28 patients with SVPTC, 85.7% were female, mean age was 45.18 years and mean tumor diameter was 2.96 cm. Microscopically; tumors had a solid growth pattern amounting to at least 50.0% of the tumor volume. In all cases the tumor cells had characteristic nuclear features of conventional PTC. 11 patients had multifocal tumors, extrathyroidal extension was present in 4 patients and vascular invasion was observed in 7 cases. Regional lymph node metastases were noted in 2 (7.1%) cases at the time of diagnosis. One patient died because of locally advanced disease. Another patient is alive with lung metastases after 48 months from the initial surgery. There was no evidence of local recurrence in other patient.

CONCLUSIONS

SVPTC is a rare variant of PTC that should be considered in the differential diagnosis of tumors which show a solid/trabecular growth pattern in the thyroid. It has poor prognostic features such as widespread angioinvasion, extrathyroidal extention, lymph node metastasis, and distant organ metastasis. Multicenter studies involving large number of cases are needed to reveal the prognostic significance of SVPTC, with standardized diagnostic criteria.

Clinicopathological Characteristics and Prognosis of Poorly Differentiated Thyroid Carcinoma Diagnosed According to the Turin Criteria

OBJECTIVE

Poorly differentiated thyroid carcinoma (PDTC) is the primary cause of death in patients with nonanaplastic follicular cell-derived thyroid carcinoma. We purposed to identify the clinical and pathological characteristics of PDTC and their relationship with prognosis.

METHODS

A retrospective analysis was conducted on patients diagnosed with PDTC at our institution from 2010 to 2018. All of their histopathology slides were reviewed by 2 experienced pathologists based on the Turin criteria. Furthermore, information regarding clinical characteristics, pathological characteristics, treatment strategy, and follow-up events were collected. The Kaplan-Meier method was used for survival analysis, while the log-rank test was used to compare survival curves. Then, the Cox proportional hazards model was used to perform univariate and multivariate analyses.

RESULTS

Twenty-six patients with PDTC who met the Turin criteria were enrolled in this study. The median follow-up period of the included 26 patients was 76 months, while the 3- and 5-year survival rates were 40% and 18%, respectively. Notably, univariate analysis revealed that tumor size >4 cm (P = .038), extrathyroidal extension (ETE) (P = .020), distant metastases (P = .047), poorly differentiated areas >60% (P = .049), and Ki-67 labeling index >30% (P = .040) were associated with poor prognosis. On the other hand, multivariate analysis identified ETE (P = .007) and distant metastases (P = .031) as independent risk factors for poor prognosis.

CONCLUSION

PDTC is a rare carcinoma with high invasiveness and poor prognosis. Patients with ETE or distant metastases may have adverse outcomes.

Ki67 in endocrine neoplasms: to count or not to count, this is the question! A systematic review from the English language literature

BACKGROUND

Endocrine neoplasms are generally slow-growing tumors that can show hormonal activity and give metastases. In most cases they are benign and clearly malignant forms are easy to diagnose. However, borderline forms may occur and be, for the pathologists, very difficult to classify. In these cases, there is a strong need to identify factors that may aid. Official classification systems for endocrine neoplasms are based on the evaluation of proliferation and, in most cases, they rely on mitotic count. In support, the study of Ki67 is carried out which, however, has not yet been included in any official classification system, except for neuroendocrine neoplasms of the gastro-entero-pancreatic tract.

PURPOSE

The aim of the present study was to investigate the proven or unproven role of Ki67 in endocrine neoplasms, in different districts, in order to bring to light the substantial differences, in terms of proliferation, existing between neoplasms so similar, but at the same time, so different.

METHODS

A thorough search of English language literature was performed, looking for articles concerning Ki67 in five endocrine neoplasms (pituitary adenomas, thyroid neoplasms, adrenocortical neoplasms, pheochromocytomas and paragangliomas).

RESULTS

From 2170, 236 articles were selected and it was seen that the endocrine neoplasm in which Ki67 was most studied was the pituitary, where it still shows a controversial role. In other neoplasms different roles were identified.

CONCLUSION

The pathologist should be aware of the contribution that this proliferative marker can give to the diagnosis and, sometimes, to the therapy selection, for the clinician.

Poorly differentiated thyroid carcinoma of childhood and adolescence: a distinct entity characterized by DICER1 mutations

Poorly differentiated thyroid carcinomas (PDTC) in young individuals are rare and their clinical and histopathologic features, genetic mechanisms, and outcomes remain largely unknown. Here, we report a detailed characterization of a series of six PDTC in patients ≤21 years old defined by Turin diagnostic criteria studied for mutations and gene fusions characteristic of thyroid cancer using targeted next-generation sequencing (NGS) and whole-exome sequencing (WES). All tumors had solid, insular, or trabecular growth pattern and high mitotic rate, and five out of six tumors showed tumor necrosis. Targeted NGS assay identified somatic mutations in the DICER1 gene in five of six (83%) tumors, all of which were "hotspot" mutations encoding the metal-ion binding sites of the RNase IIIb domain of DICER1. WES was performed in five cases which confirmed all hotspot mutations and detected two tumors with additional inactivating DICER1 alterations. Of these two, one was a germline pathogenic DICER1 variant and the other had loss of heterozygosity for DICER1. No other mutations or gene fusions characteristic of adult well-differentiated thyroid cancer and PDTC (BRAF, RAS, TERT, RET/PTC, and other) were detected. On follow-up, available for five patients, three patients died of disease 8-24 months after diagnosis, whereas two were alive with no disease. The results of our study demonstrate that childhood- and adolescent-onset PDTC are genetically distinct from adult-onset PDTC in that they are strongly associated with DICER1 mutations and may herald DICER1 syndrome in a minority. As such, all young persons with PDTC may benefit from genetic counseling. Furthermore, their clinically aggressive behavior contrasts sharply with the indolent nature of the great majority of thyroid tumors with DICER1 mutations reported to date.

Poorly differentiated thyroid carcinoma

Poorly differentiated thyroid carcinoma (PDTC) is an aggressive form of follicular cell derived thyroid carcinoma with a prognosis intermediate between the indolent well differentiated thyroid carcinomas and the rapidly growing often fatal anaplastic carcinoma. While all investigators agree on the presence of this entity, there is disagreement in regard to its definition. In 2006, a set of criteria based solely on mitotic index ≥5/10 high power fields and/or tumor necrosis was proposed by a group of researchers from Memorial Sloan Kettering Cancer Center (MSKCC criteria) in New York. A year later, alternative diagnostic criteria of PDTC, so called the Turin proposal, were advocated by an international consensus group. The Turin proposal requires three criteria: 1) solid/trabecular/insular growth pattern; 2) absence of nuclear features of papillary carcinoma; and 3) at least one of the following three features: mitotic index ≥3/10 high power fields (HPFs), necrosis, or convoluted nuclei. In this review, we summarize the histology, diagnostic criteria (Turin proposal and MSKCC criteria) with their pros and cons, the prognostic factors, and molecular profile of PDTC, aiming to provide a practical and compreshensive review of this challenging entity.

Histopathology and immunohistochemistry as prognostic factors for poorly differentiated thyroid cancer in a series of Polish patients

Background

Poorly differentiated thyroid cancer (PDTC) is a rare but aggressive type of thyroid cancer (TC) and the main cause of death from non-anaplastic follicular cell-derived TC. Although the Turin criteria are well defined, the pathological features that could serve as diagnostic and prognostic factors remain controversial.

Materials and methods

Forty-nine consecutive PDTC cases were identified in a single cancer center between 2000 and 2018. We analyzed the impact of routine histopathological and immunohistochemical features and several parameters that are not routinely included in pathology reports such as the presence of atypical mitoses, the amount of necrosis, or insulin-like growth factor-II mRNA-binding protein 3 immunostaining on the survival of patients with PDTC. Overall survival (OS) and disease-specific survival (DSS) were calculated using the Kaplan-Meier method.

Results

Of the 49 PDTC 34 (69.4%) showed the insular pattern of growth. The median of poorly differentiated area was 95% (range, 1–100), and 30 (61.2%) patients had a predominant (>50%) insular area. The 5-year OS and DSS rates at a median follow-up of 57 months were 60.6% and 64.3%, respectively. Univariate analysis showed that tumor size >4 cm, presence of atypical mitoses, Ki-67 >5%, and thyroglobulin (Tg)-negative immunostaining were associated with a higher risk of PDTC-related death. Atypical mitoses and Tg negativity were independent factors of worse DSS in multivariate analysis. Patients with insular and predominant insular areas showed a 3- and 6-fold higher risk of PDTC death when they displayed atypical mitoses.

Conclusions

In PDTC, the presence of atypical mitoses may be helpful in identifying patients with poorer outcome and worth including in pathology reports, particularly in tumors with a dominant insular pattern of growth. Additionally, the inclusion of Tg immunostaining may be considered in a prognostic context, and not only as a diagnostic feature.

Prognostic Impact of the Turin Criteria in Poorly Differentiated Thyroid Carcinoma

BACKGROUND

The Turin criteria including solid, trabecular, and/or insular architecture, lack of typical nuclear features of papillary carcinoma, and mitoses, necrosis, or convoluted nuclei were adopted in the recent 4th edition of the World Health Organization classification published in 2017.

MATERIALS AND METHODS

Between 2006 and 2017, 11,001 cases underwent initial surgery for primary malignant thyroid tumor derived from follicular cells. A total of 75 (0.7%) cases were diagnosed with PDTC according to the 2004 WHO classification. Based on the Turin criteria, 30 (40%) cases were re-classified as PDTC-Turin (+) and 45 (60%) cases were PDTC-Turin (-). Clinicopathological features and prognosis were compared between PDTC-Turin (+) and PDTC-Turin (-).

RESULTS

Seventy-five patients (48 females and 27 males) had a median age at the time of surgery of 57 years. Preoperative diagnosis was benign in 16 (21%), follicular tumor in 40 (53%), and malignant in 19 (25%). The 5-year cause-specific survival (CSS) and disease-free survival (DFS) rates were 97% and 44% for PDTC-Turin (+) and 100% and 88% for PDTC-Turin (-). On univariate analysis, CSS and DFS rates were significantly worse in the PDTC-Turin (+) than in the PDTC-Turin (-) (p = 0.0096, and p = 0.0016). Multivariate analysis showed that Turin criteria status, Ki-67 labeling index ≥ 10%, and age 55 ≥ years were the independent prognostic factors for recurrence.

CONCLUSIONS

The prevalence of PDTC diagnosed with the Turin criteria was low, but it showed more aggressive behavior. The 2017 WHO classification reflects the prognosis more accurately than the 2004 WHO classification.

Thyroid Tumors You Don't Want to Miss

This article examines more uncommon thyroid entities, including anaplastic thyroid carcinoma, poorly differentiated thyroid carcinoma, rare papillary thyroid carcinoma variants, medullary thyroid carcinoma, non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), and multiple adenomatous nodules in the setting of Cowden syndrome. These entities were chosen based on their clinical significance and because they can be diagnostically challenging due to their morphologic diversity and overlap with other thyroid tumors. This article addresses the diagnostic features of each entity, focusing on how to avoid potential pitfalls and mimics while also highlighting the clinical implications of each diagnosis.

Increased Anaplastic Lymphoma Kinase Activity Induces a Poorly Differentiated Thyroid Carcinoma in Mice

Background: Radioiodine refractory dedifferentiated thyroid cancer is a major clinical challenge. Anaplastic lymphoma kinase (ALK) mutations with increased ALK activity, especially fusion genes, have been suggested to promote thyroid carcinogenesis, leading to development of poorly differentiated thyroid carcinoma (PDTC) and anaplastic thyroid carcinoma. To determine the oncogenic potential of increased ALK activity in thyroid carcinogenesis in vivo, we studied mice with thyrocyte-specific expression of a constitutively active ALK mutant. Methods: Mice carrying a Cre-activated allele of a constitutively active ALK mutant (F1174L) were crossed with mice expressing tamoxifen-inducible Cre recombinase (CreER^T2) under the control of the thyroglobulin (Tg) gene promoter to achieve thyrocyte-specific expression of the ALK mutant (ALK^F1174L mice). Survival, thyroid hormone serum concentration, and tumor development were recorded. Thyroids and lungs were studied histologically. To maintain euthyroidism despite dedifferentiation of the thyroid, a cohort was substituted with levothyroxine (LT4) through drinking water. Results: ALK^F1174L mice developed massively enlarged thyroids, which showed an early loss of normal follicular architecture 12 weeks after tamoxifen injection. A significant decrease in Tg and Nkx-2.1 expression as well as impaired thyroid hormone synthesis confirmed dedifferentiation. Histologically, the mice developed a carcinoma resembling human PDTC with a predominantly trabecular/solid growth pattern and an increased mitotic rate. The tumors showed extrathyroidal extension into the surrounding strap muscles and developed lung metastases. Median survival of ALK^F1174L mice was significantly reduced to five months after tamoxifen injection. Reduced Tg expression and loss of follicular structure led to hypothyroidism with elevated thyrotropin (TSH). To test whether TSH stimulation played a role in thyroid carcinogenesis, we kept ALK^F1174L mice euthyroid by LT4 substitution. These mice developed PDTC with identical histological features compared with hypothyroid mice, demonstrating that PDTC development was due to increased ALK activity and not dependent on TSH stimulation. Conclusion: Expression of a constitutively activated ALK mutant in thyroids of mice leads to development of metastasizing thyroid cancer resembling human PDTC. These results demonstrate in vivo that increased ALK activity is a driver mechanism in thyroid carcinogenesis.

Prognostic Significance of Extent of Invasion in Poorly Differentiated Thyroid Carcinoma

Background: The 2017 World Health Organization (WHO) Classification of Tumors of Endocrine Organs defines poorly differentiated thyroid carcinoma (PDTC) as a tumor with conventional criteria of malignancy (capsular penetration or vascular invasion) with solid, insular, or trabecular growth, a lack of nuclear features of papillary thyroid carcinoma, and increased mitotic activity, tumor necrosis, or convoluted nuclei. The extent of invasion has been shown to be prognostic in follicular thyroid carcinoma and Hürthle cell carcinoma. Our aim was to evaluate how extent of invasion impacts clinical outcome for PDTC. Methods: We retrospectively identified 47 consecutively diagnosed cases of PDTC that were resected between 2005 and 2018. All cases were reviewed to confirm that the tumors met the 2017 Endocrine WHO criteria of PDTC. In addition, tumors were categorized as follows: encapsulated with capsular penetration only, encapsulated with focal vascular invasion (fewer than four foci), encapsulated with extensive vascular invasion (four or more foci), or widely invasive. Histopathologic characteristics and clinical outcome data were recorded. Results: A total of 47 cases of PDTC, including 15 oncocytic tumors, were identified from 28 (60%) women and 19 (40%) men (mean age of 57 years at diagnosis). The mean tumor size was 4.3 cm. Mitoses numbered 8 per 10 high-power fields (HPF) on average (range: 1-34), and necrosis was present in 21 (45%) cases. Eight (17%) cases were encapsulated with capsular penetration only, 5 (11%) were encapsulated with focal vascular invasion, 18 (38%) were encapsulated with extensive vascular invasion, and 16 (34%) were widely invasive. Of the 42 (89%) patients with follow-up data, 7 (17%) died of disease (with a mean survival time of 6.4 years), 11 (26%) have distant metastatic disease, and 24 (57%) have no evidence of disease (mean follow-up 5.6 years). Eight (19%) patients presented with M1 disease at diagnosis. The 5-year disease-free survival (DFS) for patients with M0 disease at diagnosis was 100% for patients with tumors with capsular invasion only or focal vascular invasion (n = 7), 73% for patients with encapsulated tumors with extensive vascular invasion (n = 11), and 17% for patients with widely invasive PDTCs (n = 6). DFS estimates by Kaplan-Meier analysis were significantly different between these groups (p = 0.0016). Conclusions: Extent of invasion appears to be an important parameter that affects clinical outcome for patients with PDTC. In our cohort, patients with encapsulated PDTC with capsular invasion only or focal vascular invasion had an excellent outcome.

Poorly Differentiated Carcinoma of the Thyroid Gland: Current Status and Future Prospects

BACKGROUND

Poorly differentiated thyroid cancer (PDTC) is a rare but clinically highly significant entity because it accounts for most fatalities from non-anaplastic follicular cell-derived thyroid cancer. Due to the relative rarity of the disease and heterogeneous diagnostic criteria, studies on PDTC have been limited. In light of the evolution of ultra-deep next-generation sequencing technologies and through correlation of clinicopathologic and genomic characteristics of PDTC, an improved understanding of the biology of PDTC has been facilitated. Here, the diagnostic criteria, clinicopathologic characteristics, management, and outcomes in PDTC, as well as genomic drivers in PDTC reported in recent next-generation sequencing studies, are reviewed. In addition, future prospects in improving the outcomes in PDTC patients are reviewed.

SUMMARY

PDTC patients tend to present with adverse clinicopathologic characteristics: older age, male predominance, advanced locoregional disease, and distant metastases. Surgery with clearance of all gross disease can achieve satisfactory locoregional control. However, the majority of PDTC patients die of distant disease. Five-year disease-specific survival for PDTC patients has been reported at 66%. On multivariate analysis, reported predictors of poor survival in PDTC patients have been older age (>45 years), T4a pathological stage, extrathyroidal extension, high mitotic rate, tumor necrosis, and distant metastasis at presentation. BRAF^V600E or RAS mutations (27% and 24% of cases, respectively) remain mutually exclusive main drivers in PDTC. TERT promoter mutations represent the most common alteration in PDTC (40%). Mutation in translation initiation factor EIF1AX (11%) and tumor suppressor TP53 (16%) have also been reported in PDTC. High rates of novel mutations (MED12 and RBM10) have been reported in fatal PDTC (15% and 12%, respectively). Chromosome 1q gains represent the most common arm-level alterations in PDTC, and those patients show worse survival rates. Chromosome 22q losses are also found in PDTC and show strong association with RAS mutation.

CONCLUSIONS

These new insights into the clinicopathologic and molecular characteristics of PDTC, together with further advancement in ultra-deep sequencing technologies, will be conducive in narrowing the focus in order to develop novel targeted therapies and improve the outcomes in PDTC patients.

Poorly Differentiated Thyroid Carcinoma Patients with Detectable Thyroglobulin Levels after Initial Treatment Show an Increase in Mortality and Disease Recurrence

PURPOSE

The role of thyroglobulin (Tg) in predicting death and recurrence risk in patients with poorly differentiated thyroid carcinoma (PDTC) is not well established. We aimed to analyze Tg levels following total thyroidectomy and adjuvant radioiodine treatment (RAI) in PDTC patients and correlate Tg levels with survival and recurrence.

METHODS

A retrospective analysis was conducted on 101 patients with PDTC who were treated between 1986 and 2010. Among them, 38 had no distant metastases at presentation, were managed by total thyroidectomy and adjuvant RAI, and had negative anti-Tg antibodies. An unstimulated Tg level < 1 ng/mL was used as a cut-off point for undetectable Tg levels. Association of patient and tumor characteristics with Tg levels was examined by χ² test. Overall survival, disease-specific survival (DSS), and recurrence-free survival (RFS), stratified by Tg levels, were calculated by the Kaplan-Meier method and compared by the log-rank test.

RESULTS

Compared to patients with undetectable Tg, cases with detectable Tg had a lower probability of achieving free surgical margins (21.7 vs. 46.7%; p = 0.04), higher node status (73.3 vs. 21.8%; p = 0.005), decreased 5-year DSS (65 vs. 100%; p = 0.009), and worse 5-year RFS (32 vs. 84%, p = 0.010), with a significant number of patients having a recurrence in the first year (50 vs. 12.5%; p = 0.021). Patients with detectable Tg levels also showed worse locoregional (55.6 vs. 90.9%; p = 0.014) and distant control (5-year distant control of 46.9 vs. 91%; p = 0.017).

CONCLUSIONS

Our results suggest that detectable Tg levels after surgery and RAI in a subset of PDTC patients appear to predict a higher rate of death and recurrence.

Atypical Features Resembling Poorly Differentiated Thyroid Carcinoma Presenting Entirely within a Follicular Adenoma

Poorly differentiated thyroid carcinoma (PDTC) is rare and is usually widely invasive at presentation. Here we present an unusual case with a component meeting diagnostic criteria for PDTC by Turin consensus proposal arising within a follicular adenoma. A 44-year-old female was found to have an incidental right thyroid nodule that was suggestive of follicular neoplasm on FNA. Histological examination of hemithyroidectomy revealed an 11 mm focus with insular growth pattern, alteration in cell morphology, and high mitotic count meeting criteria for PDTC. In addition there were several regions showing trabecular architecture with increased mitotic activity but not meeting criteria for PDTC. The literature for such cases is sparse but suggests much better prognosis than conventional invasive PDTC, although a biological potential for aggressive behaviour may be possible.

The diagnostic and prognostic values of Ki-67/MIB-1 expression in thyroid cancer: a meta-analysis with 6,051 cases

Background

Growing evidence has demonstrated that Ki-67/MIB-1 has an effect on the clinical progression and prognosis in cancers. However, the diagnostic and prognostic values of Ki-67/MIB-1 in thyroid cancer remain unclear.

Materials and methods

The meta-analysis was conducted in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Studies were retrieved from PubMed, EBSCO, EMBASE, ISI Web of Science, China National Knowledge Infrastructure, WanFang and Chinese VIP databases. MetaDiSc and STATA12.0 were used to analyze the meta-analysis. Fixed-effect analysis and random-effect analysis were applied to pool the relative ratio based on heterogeneity in this meta-analysis.

Results

In the meta-analysis, 51 eligible studies were included. The pooled sensitivity of Ki-67/MIB-1 was 0.61 (95% confidence interval [CI]: 0.59–0.63) and specificity was 0.75 (95% CI: 0.74–0.77) in thyroid cancer. The pooled positive likelihood ratio was 3.19 (95% CI: 2.30–4.42) and negative likelihood ratio was 0.43 (95% CI: 0.35–0.54). In the diagnosis of thyroid cancer, the pooled diagnostic odds ratio of Ki-67/MIB-1 was 8.54 (95% CI: 5.03–14.49). The area under the symmetric receiver operating characteristic curve was 0.804 (standard error =0.031). Our results showed that there were statistical associations between Ki-67/MIB-1 and age (odds ratio [OR] =1.71, 95% CI: 1.14–2.57, P=0.010), tumor size (OR =1.86, 95% CI: 1.17–2.96, P=0.008), lymph node metastasis (OR =2.49, 95% CI: 1.42–4.39, P=0.002), metastasis status (OR =6.96, 95% CI: 2.46–19.69, P<0.001), tumor node metastasis stage (OR =6.56, 95% CI: 3.80–11.34, P<0.001) and extrathyroid extension (OR =1.91, 95% CI: 1.27–2.87, P=0.002). Furthermore, thyroid cancer patients with a high level of Ki-67/MIB-1 had a worse disease-free survival as compared to patients with a low level of Ki-67/MIB-1 (hazard ratio =5.19, 95% CI: 3.18–8.46, P<0.001). Also, Ki-67/MIB-1 was found to be associated with increased risk of mortality (hazard ratio =3.56, 95% CI: 1.17–10.83, P=0.025).

Conclusion

Our results demonstrated that Ki-67/MIB-1 might act as a potential factor in diagnosing thyroid cancer in Chinese. Also, the meta-analysis indicated that Ki-67/MIB-1 might have an effect on prognosis in non-Chinese thyroid cancer patients.

Prognostic implication of histological features associated with EHD2 expression in papillary thyroid carcinoma

Papillary thyroid carcinoma (PTC) is a heterogeneous tumor with various histological and molecular subtypes. EHD2 is involved in endocytosis and endosomal recycling. This study aimed to investigate the prognostic significance of EHD2 expression in PTC and develop a new model for predicting persistent/recurrent disease after thyroidectomy. Pathologic slides of 512 consecutive patients with PTC ≥ 1 cm were retrospectively reviewed. BRAF mutation analysis and immunohistochemistry for EHD2 were performed. Clinical significance of EHD2 mRNA expression was analyzed in 388 PTC patients using The Cancer Genome Atlas dataset. The presence of dyscohesive cells and psammoma bodies were found have significant association with persistent/recurrent disease (p = 0.049 and p = 0.038, respectively). The best discrimination of disease-free survival was found by dividing patients into three prognostic groups based on the following two risk factors according to the size category: psammoma bodies ≥ 4 and dyscohesive cells (≥ 1% and ≥ 20% in PTCs of < 2.0 cm and ≥ 2.0 cm, respectively). In PTCs of ≥ 2.0 cm, patients with the two risk factors had a hazard ratio of 13.303 (p = 0.005) compared to those without risk factors. High expression level of EHD2 was associated with BRAF V600E (p < 0.001), presence of dyscohesive cells (p = 0.010), and absence of psammoma bodies (p = 0.001). Increased EHD2 mRNA expression level was associated with extrathyroidal extension (p < 0.001), pT3-4 (p < 0.001), lymph node metastasis (p < 0.001), higher risk of recurrence (p < 0.001), and BRAF V600E (p < 0.001). Our prognostic model is useful for predicting persistent/recurrent disease after surgery of PTC. EHD2 mRNA expression could be a novel prognostic marker for PTC patients.

Aggressiveness of the tall cell variant of papillary thyroid carcinoma is independent of the tumor size and patient age

The tall cell variant (TCV) of papillary thyroid carcinoma (PTC) is characterized by tall columnar cells with a height of at least three times their width. TCV usually presents at an older age, has a larger size and exhibits more extrathyroidal extension and metastases than classical PTC. The current study compared TCV with the classical and follicular variants (CaFVs) of PTC to determine if, irrespective of the age at diagnosis and tumor size, TCV is more aggressive than its classical and follicular counterparts. A total of 16 (3.66%) patients with TCV were identified in a series of 437 patients with PTC from the Clinical University Hospital (Santiago de Compostela, Spain) between 1990 and 2010. The patient clinicopathological features and B-Raf proto-oncogene (BRAF)V600E mutational status were compared with 34 cases of CaFVs of PTC matched for tumor size and patient age. The TCV series included 11 females and 5 males aged 15–74 years (median, 57 years). In total, 15 (93.8%) patients underwent total or near-total thyroidectomy, 1 underwent lobectomy and 5 (31.3%) underwent lymph node dissection. In the TCV series, the tumor size ranged from 5–45 mm (median, 19 mm). Compared with the CaFVs, the TCV of PTC exhibited a significantly higher prevalence of extrathyroidal extension [9/16 (56.3%) vs. 5/34 (14.7%) cases; P=0.007], lymph node metastases [9/16 (56.3%) vs. 9/34 (26.4%) cases; P=0.04], stage III/IV at presentation [10/16 (62.5%) vs. 7/34 (20.5%) cases; P=0.009] and BRAFV600E mutation [12/16 (80.0%) vs. 7/25 (28.0%) cases; P=0.004]. The TCV series also harbored more multifocal papillary carcinomas (50.0% vs. 26.4%), lymphovascular invasion (37.5% vs. 29.4%) and distant metastases (6.2% vs. 0.0%), as compared with the matched patient cohort. In conclusion, the TCV of PTC is frequently associated with BRAFV600E mutation and is more aggressive than the CaFVs of PTC, regardless of tumor size and patient age at diagnosis.

Nonanaplastic follicular cell-derived thyroid carcinoma: mitosis and necrosis in long-term follow-up

Nonanaplastic follicular cell-derived thyroid carcinoma (NAFCTC) includes differentiated- (DTC) and poorly differentiated thyroid carcinoma (PDTC). DTC has an excellent prognosis, while PDTC is situated between DTC and anaplastic carcinomas. Short-term studies suggest that PDTC patients diagnosed only on tumor necrosis and/or mitosis have a prognosis similar to those diagnosed according to the TURIN proposal. The purpose of this study was to evaluate prognosis for NAFCTC based on long-term follow-up illuminating the significance of tumor necrosis and mitosis. A cohort of 225 patients with NAFCTC was followed more than 20 years. Age, sex, distant metastasis, histology, tumor size, extrathyroidal invasion, lymph node metastasis, tumor necrosis and mitosis were examined as possible prognostic factors. Median follow-up time for patients alive was 28 years (range 20-43 years). Age, distant metastasis, extrathyroidal invasion, tumor size, tumor necrosis and mitosis were independent prognostic factors in multivariate analysis for overall survival (OS). In disease specific survival (DSS) age was not significant. Using only necrosis and/or mitosis as criteria for PDTC the 5-, 10- and 20-year OS for DTC was 87, 79 and 69%, respectively. In DSS it was 95, 92 and 90%. For PDTC the 5-, 10- and 20-year OS was 57, 40 and 25%, respectively. In DSS it was 71, 55 and 48%. Tumor necrosis and mitosis are highly significant prognostic indicators in analysis of long time survival of nonanaplastic follicular cell-derived thyroid carcinoma indicating that a simplification of the actually used criteria for poorly differentiated carcinomas may be justified.

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.

2015 American Thyroid Association Management Guidelines for Adult Patients with Thyroid Nodules and Differentiated Thyroid Cancer: The American Thyroid Association Guidelines Task Force on Thyroid Nodules and Differentiated Thyroid Cancer

BACKGROUND

Thyroid nodules are a common clinical problem, and differentiated thyroid cancer is becoming increasingly prevalent. Since the American Thyroid Association's (ATA's) guidelines for the management of these disorders were revised in 2009, significant scientific advances have occurred in the field. The aim of these guidelines is to inform clinicians, patients, researchers, and health policy makers on published evidence relating to the diagnosis and management of thyroid nodules and differentiated thyroid cancer.

METHODS

The specific clinical questions addressed in these guidelines were based on prior versions of the guidelines, stakeholder input, and input of task force members. Task force panel members were educated on knowledge synthesis methods, including electronic database searching, review and selection of relevant citations, and critical appraisal of selected studies. Published English language articles on adults were eligible for inclusion. The American College of Physicians Guideline Grading System was used for critical appraisal of evidence and grading strength of recommendations for therapeutic interventions. We developed a similarly formatted system to appraise the quality of such studies and resultant recommendations. The guideline panel had complete editorial independence from the ATA. Competing interests of guideline task force members were regularly updated, managed, and communicated to the ATA and task force members.

RESULTS

The revised guidelines for the management of thyroid nodules include recommendations regarding initial evaluation, clinical and ultrasound criteria for fine-needle aspiration biopsy, interpretation of fine-needle aspiration biopsy results, use of molecular markers, and management of benign thyroid nodules. Recommendations regarding the initial management of thyroid cancer include those relating to screening for thyroid cancer, staging and risk assessment, surgical management, radioiodine remnant ablation and therapy, and thyrotropin suppression therapy using levothyroxine. Recommendations related to long-term management of differentiated thyroid cancer include those related to surveillance for recurrent disease using imaging and serum thyroglobulin, thyroid hormone therapy, management of recurrent and metastatic disease, consideration for clinical trials and targeted therapy, as well as directions for future research.

CONCLUSIONS

We have developed evidence-based recommendations to inform clinical decision-making in the management of thyroid nodules and differentiated thyroid cancer. They represent, in our opinion, contemporary optimal care for patients with these disorders.

Prognostic classification of thyroid follicular cell tumors using Ki-67 labeling index: risk stratification of thyroid follicular cell carcinomas

This review emphasizes that the so-called high-risk thyroid carcinoma is not a distinct tumor entity, but a group of tumors with different histologies. High-grade histological features, such as tumor necrosis, increased mitoses, and nuclear pleomorphism, together with high Ki-67 labeling index (more than 10%), are good indicators of high-risk thyroid carcinoma and suggest a possible risk for anaplastic transformation. This review proposes the stratification of patients with thyroid carcinoma into low-, moderate-, and high-risk groups based on Ki-67 labeling index, which should be useful for the clinical management of patients, even after initial surgery. Currently, both the aggressive variant of papillary carcinoma and poorly differentiated carcinoma are aggressively treated by a completion of total thyroidectomy with prophylactic lymph node dissection followed by radioactive iodine treatment. Therefore, patients with moderate-risk or high-risk thyroid carcinoma based on Ki-67 labeling index should also be considered candidates for this treatment strategy.

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.