Prognostic factors of minimally invasive follicular thyroid carcinoma: extensive vascular invasion significantly affects patient prognosis

Selection Criteria for Completion Thyroidectomy in Follicular Thyroid Carcinoma Using Primary Tumor Size and TERT Promoter Mutational Status

BACKGROUND

A stepwise surgical approach with hemithyroidectomy and completion thyroidectomy was used to achieve definite characterization of follicular thyroid carcinoma (FTC). Choosing appropriate candidates for completion thyroidectomy has been controversial.

OBJECTIVE

The aim of this study was to clarify the selection criteria for completion thyroidectomy using telomerase reverse transcriptase (TERT) promoter mutation.

METHODS

A total of 87 FTC patients who had information about TERT promoter mutation from August 1995 to November 2020 were investigated. The cumulative risk of initial distant metastasis, disease recurrence, and cancer-specific death according to primary tumor size in each of the World Health Organization (WHO) 2017 classifications were calculated.

RESULTS

Of the 87 patients, 8 (9.2%) had initial distant metastasis and 15 (17.2%) had persistent disease or developed structural recurrence. The threshold diameter for initial distant metastasis, disease recurrence, and cancer-specific death was 2 cm in minimally invasive FTC (MI-FTC) with mutant TERT (M-TERT) and in encapsulated angioinvasive FTC (EA-FTC) with M-TERT, while that in MI-FTC with wild-type TERT (WT-TERT) and EA-FTC with WT-TERT was 4 cm. The cumulative risk of initial distant metastasis, disease recurrence, and cancer-specific death according to primary tumor size in each WHO 2017 classification was significantly different only in patients with WT-TERT (p = 0.001, p = 0.019, and p = 0.005, respectively).

CONCLUSIONS

The data suggest 2 cm as a critical threshold diameter for performance of completion thyroidectomy in MI-FTC with M-TERT and EA-FTC with M-TERT. TERT promoter mutational status can help select candidates for completion thyroidectomy.

Challenges in Encapsulated Follicular-Patterned Tumors: How Much Is Enough? Evaluation of Nuclear Atypia, Architecture, and Invasion

Thyroid pathology is notoriously fraught with high interobserver variability, and follicular-patterned tumors are among some of the most challenging to assess accurately and reproducibly. Given that encapsulated or well-circumscribed follicular-patterned tumors often have similar molecular profiles, that is, frequent RAS or RAS-like alterations, the diagnosis usually relies on histopathologic examination alone. Unfortunately, many of the features that are used for diagnosis and prognosis of these tumors have long been controversial and frequently debated topics, both due to their subjectivity and their evolving (or not yet resolved) definitions. In more recent years, the introduction of noninvasive follicular thyroid neoplasm with papillary-like nuclear features has added further complexity to this discussion. In particular, the criteria and significance of nuclear features of papillary thyroid carcinoma, architectural patterns, and invasive growth still pose significant diagnostic challenges and confusion. This review explores some of the challenges in evaluating encapsulated follicular-patterned tumors, focusing on those histologic elements.

The Prognostic Impact of Extent of Vascular Invasion in Follicular Thyroid Carcinoma

BACKGROUND

Encapsulated angioinvasive follicular thyroid carcinoma (EAFTC) is associated with an increased risk of distant metastasis and reduced survival compared to minimally invasive follicular thyroid carcinoma (MIFTC). There is controversy regarding the extent of surgery and adjuvant radioactive iodine therapy for angioinvasive follicular thyroid carcinoma when stratified by number of foci of angioinvasion.

METHODS

All follicular thyroid carcinoma cases from 1990-2018 were identified from a thyroid cancer database. Primary outcomes were distant metastasis-free survival (DMFS) and disease-specific survival (DSS) with factors of interest being age, gender, tumour size, treatment, foci of angioinvasion and histological subtype.

RESULTS

A total of 292 cases were identified; 139 MIFTC, 141 EAFTC and 12 widely invasive follicular thyroid carcinoma (WIFTC). Over a follow-up period of 6.25 years, DMFS was significantly reduced (p < 0.001) with 14.2% (EAFTC) and 50% of WIFTC developing metastasis. The risk of metastasis in EAFTC with ≥ 4 foci of angioinvasion was 31.7% (HR = 5.89, p = 0.004), 6.3% for EAFTC with < 4 foci of angioinvasion (HR = 1.74, p = 0.47), compared to 3.6% MIFTC. Age ≥ 50 years (HR = 4.24, p = 0.005) and tumour size (HR = 1.27, p = 0.014) were significantly associated with increased risk of distant metastasis. DSS was reduced significantly (p < 0.001), with 7.8% EAFTC patients dying of disease. For EAFTC patients, DSS was 96.8% for < 4 foci and 82.6% for ≥ 4 foci of angioinvasion (p = 0.003).

CONCLUSION

EAFTC is at increased risk of distant metastasis related to the extent of angioinvasion. Tumours with < 4 foci of angioinvasion should be considered for a total thyroidectomy, particularly in older patients.

Prognostic factors for follicular thyroid carcinoma: the importance of vascular invasion

The World Health Organization (WHO) classifies follicular thyroid carcinoma (FTC) into three categories: minimally invasive (mFTC), encapsulated angioinvasive (eaFTC), and widely invasive (wFTC). This study investigated whether this classification is appropriate. We enrolled 523 patients who underwent initial surgery at Kuma Hospital between 1998 and 2015 and were diagnosed with FTC. Capsular invasion (CI) was classified as none, minimal (microscopic), or wide (macroscopic) invasion. Vascular invasion (VI) was divided according to the number of invasive foci into three degrees: VI(-), VI(1+), and VI(2+). For 507 M0 patients, age ≥55 years (p = 0.004), non-oxyphilic histology (p = 0.043), and male sex (p < 0.001) predicted poor distant recurrence-free survival (DR-FS) on univariate analysis; however, tumor size >4 cm and wide CI did not. The DR-FS rates significantly decreased from VI(-) to VI(2+) in a step-by-step fashion, including VI(-) vs. VI(1+) (p = 0.011) and VI(1+) vs. VI(2+) (p = 0.014). Multivariate analysis revealed that older age (p = 0.0004), non-oxyphilic histology (p = 0.041), male sex (p = 0.0052), VI(1+) (p = 0.017), and VI(2+) (p < 0.001) independently predicted distant recurrence. The DR-FS rates did not significantly differ among mFTC, wFTC/VI(-), and eaFTC/VI(1+). The DR-FS rate of eaFTC/VI(2+) was worse than that of eaFTC/VI(1+) (p = 0.042), but did not differ from that of wFTC/VI(1+/2+). Our findings suggest that subclassifying eaFTC according to the degree of VI and restricting wFTC to VI-positive cases would be better in the WHO classification. Revising the definition for wide CI is recommended.

Encapsulated Angioinvasive Follicular Thyroid Carcinoma: Prognostic Impact of the Extent of Vascular Invasion

BACKGROUND

Previous studies have reported an association between four or more foci of vascular invasion (VI) and thyroid cancer prognosis, while the current study aimed to investigate the association between extent of VI and outcome of encapsulated angioinvasive follicular thyroid carcinoma (FTC).

METHODS

The records of 303 patients with encapsulated angioinvasive FTC confirmed by surgical specimens at Ito Hospital from January 2005 to December 2014 were retrospectively reviewed. Thirteen patients had distant metastasis at diagnosis and were classified as M1.

RESULTS

Among the 290 patients with M0 encapsulated angioinvasive FTC, the 10-year disease-free survival (DFS) rate was 85.6%. Those with a VI of 1 (n = 131) or ≥ 2 (n = 159) had a 10-year DFS rate of 94.9% and 77.9% (p < 0.001), respectively, and those with a VI of 1-3 (n = 211) or ≥ 4 (n = 79) had a 10-year DFS rate of 86.3% and 83.3% (p = 0.311), respectively. Multivariate analysis identified age ≥ 55 years (p = 0.031) and VI ≥ 2 (p = 0.002) as independent negative prognostic factors for DFS. Patients with M0 encapsulated angioinvasive FTC aged ≥ 55 years and VI ≥ 2 had significantly poorer prognosis and a 10-year DFS rate of 66.4% (p < 0.001).

CONCLUSIONS

Patients with encapsulated angioinvasive FTC who had two or more foci of VI, especially patients aged ≥ 55 years, should be carefully followed-up.

Risk Factors and Prognosis for Metastatic Follicular Thyroid Cancer

BACKGROUND

Follicular thyroid cancer (FTC) is the second most common malignancy of thyroid. About 7%-23% of patients with FTC have distant metastasis. The aim of this study was to investigate the risk factors associated with distant metastasis and the impact of distant metastasis on survival in FTC patients.

METHODS

Patients with FTC were analyzed using a prospectively maintained dataset of thyroid cancer registered at a tertiary hospital in Taiwan between December 1976 and May 2020.

RESULTS

A total of 190 patients with a mean follow-up of 7.7 years were included in this study, including 29 with distant metastasis at diagnosis, 14 who developed metastasis during follow-up, and 147 without metastasis. Multivariate analysis adjusted for age, gender, tumor stage, and extrathyroidal invasion revealed old age (≥ 55 years) (adjusted odds ratio, 27.6; 95% confidence interval [CI], 8.75-86.8; P < 0.001) and extrathyroidal invasion (odds ratio, 24.1; 95% CI, 3.50-166.5; P = 0.001) were significantly associated with an increased risk of distant metastasis. Metastasis was correlated with higher cancer-specific mortality (adjusted hazard ratio, 35.5; 95% CI, 6.1-206.1; P < 0.001). In addition, patients with metastatic FTC diagnosed on initial presentation had the lowest 10-year cancer-specific survival rate (26.0%), followed by those who developed metastatic disease after initial treatment (76.6%), while patients without metastasis were all alive (100%) (P ≤ 0.002 for all comparisons).

CONCLUSIONS

Age and extrathyroidal invasion are significant risk factors for distant metastasis of FTC. Patients with metastatic FTC, especially when diagnosed on initial presentation, have dismal survival outcomes.

Prognostic significance of vascular invasion and cell-proliferation activity in widely invasive follicular carcinoma of the thyroid

Widely invasive follicular thyroid carcinoma (wi-FTC) is regarded as having an aggressive character and a dire prognosis, but it has not been known whether all wi-FTCs have a dire prognosis. Herein we retrospectively analyzed the cases of 133 patients with wi-FTCs to determine the prognostic significance of vascular invasion and cell-proliferation activity based on the Ki-67 labeling index (LI). Of the 119 patients without distant metastasis (M0), 11 (9.2%) showed recurrence during the postoperative follow-up. In a univariate analysis, the recurrence-free survival (RFS) rates of the M0 patients with vascular invasion and those with a Ki-67 LI ≥5% were significantly poorer (p = 0.0013 and p = 0.0268, respectively) than those of the patients without vascular invasion or with a Ki-67 LI <5%. Other clinicopathological factors such as patient age, gender, tumor size, and oxyphilic tumor were not significantly related to the patients' RFS. In a multivariate analysis, positive vascular invasion independently affected the RFS (p = 0.0133), but Ki-67 >5% did not (p = 0.1348). To date, only five patients have died of their thyroid carcinoma; four cases were M1. In conclusion, although M0 wi-FTC generally has a favorable prognosis, cases with positive vascular invasion or a high Ki-67 LI are likely to recur, and careful postoperative follow-up is necessary.

Pediatric Thyroid Cancer: Genetics, Therapeutics and Outcome

An increasing number of children are diagnosed with thyroid cancer. Most patients do not have an identifiable cause; however, tumor predisposition syndromes may be associated with development of both differentiated and medullary thyroid cancer. With an excellent prognosis for most patients, the goal of therapy is to optimize outcome and reduce complications. The increased knowledge of the oncogenic drivers provides opportunities to improve the accuracy of diagnosis, stratify surgery, and select systemic therapy that may be considered for neoadjuvant and adjuvant treatment. Treatment complications can be reduced by referral to regional, high-volume pediatric thyroid centers.

Outcomes for Minimally Invasive Follicular Thyroid Carcinoma in Relation to the Change in Age Stratification in the AJCC 8th Edition

BACKGROUND

Completion total thyroidectomy with radioactive iodine (RAI) therapy is not uniformly recommended for minimally invasive follicular thyroid carcinomas (MI-FTCs) without distant metastasis, but may be considered for cases with a risk factor of recurrence, such as age ≥ 45 years.

OBJECTIVE

The present study aimed to investigate the outcomes for patients with MI-FTC using a stratification age of 55 years.

METHODS

The records of 478 patients with MI-FTC confirmed by surgical specimens at Ito Hospital from January 2005 to December 2014 were retrospectively reviewed. Twenty patients had distant metastasis at diagnosis and were subsequently classified as M1.

RESULTS

Among the 478 patients with MI-FTC, univariate analysis identified that age ≥ 55 years (p = 0.002) and M1 (p < 0.001) were related to cause-specific survival. In 458 patients with M0 MI-FTC, male sex (p = 0.041), age ≥ 55 years (p = 0.001), and tumor size > 40 mm (p < 0.001) were related to poor disease-free survival (DFS) in univariate analysis. Multivariate analysis showed that age ≥ 55 years (p = 0.005) and tumor size > 40 mm (p = 0.005) were independent prognostic factors for DFS. The 10-year DFS rates of patients aged < 45 years, 45 years ≤ age < 55 years, and ≥ 55 years were 97.0%, 95.5%, and 86.4%, respectively.

CONCLUSIONS

The change in the recommended age for completion total thyroidectomy with RAI, from 45 to 55 years, seemed reasonable.

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.

Case for staged thyroidectomy

Recent modifications in the management of well-differentiated thyroid cancer have resulted in significant alterations in clinical approach. Utilizing a series of preoperative and postoperative risk factors involving both the patient and the disease pathology, we offer the term "staged thyroidectomy" to help organize these risk factors for patients and the endocrine team to optimize management. This approach is intended to incorporate our latest nuanced understanding of certain endocrine pathology and may serve to optimize patient outcomes.

The revised clinical practice guidelines on the management of thyroid tumors by the Japan Associations of Endocrine Surgeons: Core questions and recommendations for treatments of thyroid cancer

The Japan Associations of Endocrine Surgeons has developed the revised version of the Clinical Practice Guidelines for Thyroid Tumors. This article describes the guidelines translated into English for the 35 clinical questions relevant to the therapeutic management of thyroid cancers. The objective of the guidelines is to improve health-related outcomes in patients with thyroid tumors by enabling users to make their practice evidence-based and by minimizing any variations in clinical practice due to gaps in evidential knowledge among physicians. The guidelines give representative flow-charts on the management of papillary, follicular, medullary, and anaplastic thyroid carcinoma, along with recommendations for clinical questions by presenting evidence on the relevant outcomes including benefits, risks, and health conditions from patients' perspective. Therapeutic actions were recommended or not recommended either strongly (◎◎◎ or XXX) based on good evidence (😊)/good expert consensus (+++), or weakly (◎, ◎◎ or X, XX) based on poor evidence (😣)/poor expert consensus (+ or ++). Only 10 of the 51 recommendations given in the guidelines were supported by good evidence, whereas 35 were supported by good expert consensus. While implementing the current guidelines would be of help to achieve the objective, we need further clinical research to make our shared decision making to be more evidence-based.

Papillary and Follicular Thyroid Cancer in children and adolescents: Current approach and future directions

An increasing number of children are diagnosed with differentiated thyroid cancer. With an excellent prognosis for the majority of pediatric patients, the goal of therapy is to optimize outcome while reducing complications. Increased knowledge of the somatic, oncogenic driver mutations provides opportunities to improve the accuracy of diagnosis, to stratify surgery, and to treat patients with morbidly invasive or refractory disease. Treatment complications can be reduced by referral to regional, high-volume pediatric thyroid centers.

The American Association of Endocrine Surgeons Guidelines for the Definitive Surgical Management of Thyroid Disease in Adults

OBJECTIVE

To develop evidence-based recommendations for safe, effective, and appropriate thyroidectomy.

BACKGROUND

Surgical management of thyroid disease has evolved considerably over several decades leading to variability in rendered care. Over 100,000 thyroid operations are performed annually in the US.

METHODS

The medical literature from 1/1/1985 to 11/9/2018 was reviewed by a panel of 19 experts in thyroid disorders representing multiple disciplines. The authors used the best available evidence to construct surgical management recommendations. Levels of evidence were determined using the American College of Physicians grading system, and management recommendations were discussed to consensus. Members of the American Association of Endocrine Surgeons reviewed and commented on preliminary drafts of the content.

RESULTS

These clinical guidelines analyze the indications for thyroidectomy as well as its definitions, technique, morbidity, and outcomes. Specific topics include Pathogenesis and Epidemiology, Initial Evaluation, Imaging, Fine Needle Aspiration Biopsy Diagnosis, Molecular Testing, Indications, Extent and Outcomes of Surgery, Preoperative Care, Initial Thyroidectomy, Perioperative Tissue Diagnosis, Nodal Dissection, Concurrent Parathyroidectomy, Hyperthyroid Conditions, Goiter, Adjuncts and Approaches to Thyroidectomy, Laryngology, Familial Thyroid Cancer, Postoperative Care and Complications, Cancer Management, and Reoperation.

CONCLUSIONS

Evidence-based guidelines were created to assist clinicians in the optimal surgical management of thyroid disease.

The evolving concept of aggressive histological variants of differentiated thyroid cancer

It is recommended by current clinical guidelines that pathologists identify and report aggressive histological variants of differentiated thyroid cancer (e.g., tall cell, columnar cell, and hobnail variants of papillary thyroid carcinoma; widely invasive follicular thyroid carcinoma). This review analyzes the historical evolution of these entities and highlights unresolved issues with respect to the diagnostic criteria for these tumors.

Invasion in thyroid cancer: Controversies and best practices

Invasion is a key feature of malignancy and an important element in the classification, risk-stratification, and staging of thyroid cancers. However, the histopathologic criteria for tumor capsular invasion, angioinvasion, and extrathyroidal extension (ETE) have varied among pathologists, both in practice as well as in studies assessing the clinical significance of these findings. In this review, we provide historic context for the controversies surrounding the definition of invasion in thyroid neoplasms and highlight recent efforts to standardize how pathologists report capsular invasion, angioinvasion, and ETE. We offer practical suggestions for distinguishing invasion from its mimics and provide an algorithmic approach for classifying thyroid tumors based on integration of tumor invasiveness, nuclear atypia, and architectural pattern.

[Individualization of the surgical procedure in response to overdiagnosis and overtreatment in differentiated thyroid carcinomas]

BACKGROUND

Advances in diagnostic methods have led to an early detection of thyroid nodules with debatable malignant potential in numerous cases. This can result in a potential overtreatment of thyroid lesions with very good prognosis.

OBJECTIVES

To avoid surgical overtreatment, an individualized, risk-adapted management is required that respects the different tumor biology of the underlying histological entities.

METHODS

The current guidelines of the leading professional societies, the American Thyroid Association (ATA) and the German Association of Endocrine Surgeons (CAEK), were compared and critically studied, to describe risk-adapted, more conservative treatment options for certain types of thyroid neoplasms according to the 2017 WHO definition.

RESULTS

The German CAEK recommends thyroidectomy as a routine operation in the case of thyroid carcinoma. Exceptions are papillary thyroid microcarcinoma and minimally invasive follicular thyroid carcinoma, which can be treated by lobectomy. The ATA proposes an "active surveillance" for papillary thyroid microcarcinoma and lobectomy in cases of differentiated thyroid carcinoma <4 cm in diameter in the absence of clearly predefined risk factors.

CONCLUSIONS

The pre- or intraoperative pathological diagnosis of the underlying tumor entity is the key point, which allows for an adaption of the resection strategy for thyroid malignancy. Depending on the type of carcinoma, the current guidelines of international expert societies allow for parenchyma-sparing operations and, according to the ATA, even an "active surveillance."

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.

Critical Prognostic Parameters in the Anatomic Pathology Reporting of Differentiated Follicular Cell-Derived Thyroid Carcinoma

In the past decades, pathology reporting on thyroid carcinoma has evolved from a narrative approach to structured synoptic reports. Many histologic variables are present in the current synoptic reports that are crucial elements for initial risk stratification and clinical management. In this review, we compare and summarize the key prognostic pathologic characteristics utilized by the most influential clinical and pathologic guidelines from the American Thyroid Association (ATA), the National Comprehensive Cancer Network (NCCN), the current World Health Organization (WHO) classification of endocrine tumors (fourth edition), the current American Joint Committee on Cancer (AJCC) staging system (eighth edition), the College of American Pathologists (CAP) protocol, and the International Collaboration on Cancer Reporting (ICCR) dataset. The aim is to provide a comprehensive review focused on the definitions and prognostic impacts of these crucial pathologic parameters.

The surgical dilemma of primary surgery for follicular thyroid neoplasms

Follicular thyroid carcinoma is the second most prevalent form of differentiated thyroid carcinoma, following papillary thyroid carcinoma. Preoperative diagnosis is hampered by the fact that fine-needle aspiration cytology as well as supplemental molecular analysis cannot unambiguously distinguish between follicular thyroid carcinoma and benign follicular thyroid adenoma. The 2017 WHO classification defines three histological subtypes of follicular thyroid carcinoma: minimally invasive (excellent prognosis), encapsulated angioinvasive, and widely invasive type (higher risk of recurrence and metastatic spread). The fact that definite characterization of follicular neoplasms is predominantly a postoperative histological diagnosis (core criteria: capsular, vascular and adjacent tissue invasion) translates into the challenge for the thyroid surgeon to plan preoperatively for presence of malignancy and, if required, to adapt the surgical strategy according to intraoperative (frozen section) or postoperative histological findings. Until improved tools for pre-/intraoperative diagnosis are available, the malignant potential of a follicular thyroid lesion can be assessed by stratifying the patient according to clinical risk factors (presence of metastases, advanced patient age, tumor size). A stepwise, escalating surgical approach with restricted primary resection (hemithyroidectomy) and completion surgery based on the definite histopathology is another option to solve this dilemma. The currently recommended surgical treatment strategies for FTCs as published by ATA, BTA, CAEK and ESES are discussed. There is consensus that prophylactic lymphadenectomy is not required for FTCs and that hemithyroidectomy is sufficient in low-risk FTCs (capsular invasion only) whereas thyroidectomy with postoperative radioiodine therapy is indicated in high-risk FTCs (angioinvasion; widely invasive FTC).

Prediction of follicular thyroid carcinoma associated with distant metastasis in the preoperative and postoperative model

BACKGROUND

Only clinicopathological findings are reported for predicting follicular thyroid carcinoma (FTC) associated with distant metastasis, and preoperative ultrasound (US) findings are unknown.

METHODS

Associations between distant metastases of FTC and predicting factors were evaluated by using logistic regression analysis in the preoperative and postoperative models.

RESULTS

Distant metastasis was present in 37 (11.5%) of the 321 patients with FTC. In the preoperative model, independent predictors of distant metastasis were age, marked hypoechogenicity, nodule-in-nodule appearance, and rim calcification on US. Postoperative predictors were marked hypoechogenicity, rim calcification, and widely invasive histology. Sensitivities, specificities, and the area under the curves for predicting distant metastasis were 86.5%, 80.3%, and 0.889 on preoperative status and 86.5%, 78.5%, and 0.908 on postoperative status. Although not statistically significant, all four patients with gross extrathyroidal extension had metastasis.

CONCLUSION

Age, ultrasound features, and widely invasive histology allow preoperative and postoperative prediction of FTC associated with distant metastasis.

Clinically Relevant Prognostic Parameters in Differentiated Thyroid Carcinoma

Although differentiated thyroid carcinomas typically pursue an indolent clinical course, it is important to identify the subset of tumors that are most likely to behave aggressively so that patients with these tumors are counseled and treated appropriately. Extent of disease is fundamental to the prognostication for differentiated thyroid carcinoma; however, there are additional histologic features of the tumor separate from extent of disease that have been shown to affect clinical course. This review will start with a discussion of aggressive variants of papillary thyroid carcinoma, move to the prognostic significance of vascular invasion in follicular thyroid carcinoma, and finish with a discussion of Hürthle cell carcinoma, with an emphasis on why it is not considered a subtype of follicular thyroid carcinoma in the 2017 WHO Classification of Tumors of Endocrine Organs.

Follow-up of differentiated thyroid cancer - what should (and what should not) be done

The treatment paradigm for thyroid cancer has shifted from a one-size-fits-all approach to more personalized protocols that range from active surveillance to total thyroidectomy followed by radioiodine remnant ablation. Accurate surveillance tools are available, but follow-up protocols vary widely between centres and clinicians, owing to the lack of clear, straightforward recommendations on the instruments and assessment schedule that health-care professionals should adopt. For most patients (that is, those who have had an excellent response to the initial treatment and have a low or intermediate risk of tumour recurrence), an infrequent assessment schedule is sufficient (such as a yearly determination of serum levels of TSH and thyroglobulin). Select patients will benefit from second-line imaging and more frequent assessments. This Review discusses the strengths and weaknesses of the surveillance tools and follow-up strategies that clinicians use as a function of the initial treatment and each patient's risk of recurrence.

Neck Ultrasound in Patients with Follicular Thyroid Carcinoma

There are limited data on the role of neck ultrasound (US) in the surveillance of patients with follicular thyroid cancer (FTC). Here, we analyze the likelihood of US to find structural disease in patients with FTC and evaluate if initial American Thyroid Association (ATA) risk stratification and the response to therapy categories [the latter based on thyroglobulin (Tg) levels] modify that likelihood. We conducted a retrospective cohort study of 32 patients with FTC in our institution. We included all patients with well-differentiated FTC who underwent total thyroidectomy and radioactive iodine (RAI) treatment without neck structural disease at the time of RAI and with Tg and US at least 6 months after RAI. After a median follow-up of 4.3 years, two patients (6.3%) had structural disease by US. None of the 18 patients with initial ATA low-risk disease had structural disease by US in contrast to higher, but not significant, frequency of 18.2% (2/11) in patients with initial ATA high-risk disease (p = 0.14). Based on Tg levels, 24/32 patients had excellent response to therapy and 8/32 had biochemical incomplete/indeterminate response. None of the patients with excellent response had structural disease by US versus 2/8 (25%) patients with biochemical incomplete/indeterminate response all of whom had other sites of structural disease (p = 0.054). Our findings suggest that neck US in FTC is unlikely to find structural disease with initial low-risk ATA or excellent response to therapy but can detect structural disease in some patients with initial ATA high-risk or incomplete/indeterminate responses to therapy.

Crucial parameters in thyroid carcinoma reporting - challenges, controversies and clinical implications

In the modern era, a pathology report of thyroid carcinoma requires the inclusion of numerous prognostically relevant histopathological features, e.g. the presence and extent of vascular and capsular invasion, extrathyroidal extension, the surgical margin status and the characteristics of nodal metastasis. These pathological features are crucial components of the initial risk stratification to determine the need for completion thyroidectomy and/or postoperative radioactive iodine ablation therapy. The current review aims to summarise the diagnostic criteria, the controversies, the prognostic impacts and the challenges of these pathological characteristics, focusing specifically on the parameters that are incorporated into the American Joint Committee on Cancer (AJCC) staging system, the College of American Pathologists (CAP) reporting template, the American Thyroid Association (ATA) and the National Comprehensive Cancer Network (NCCN) guidelines.

Differences in the Impact of Age on Mortality in Well-Differentiated Thyroid Cancer

INTRODUCTION

Well-differentiated thyroid cancer (WDTC) is unique in that patient age is part of staging. Several studies have shown a need to increase the age threshold in staging for WDTC, but the separate impact of age on prognosis for papillary and follicular carcinomas has not been examined. We hypothesize that age impacts survival differently for papillary and follicular carcinomas.

METHODS

Patients with invasive papillary thyroid carcinoma (PTC) and follicular thyroid carcinoma (FTC) between 2004 and 2013 were identified in the National Cancer Database, and were stratified by histologic type. Overall survival (OS) was analyzed using multivariable Cox regression, and the Youden index was used to find the optimal age threshold for both histologies.

RESULTS

A total of 204,139 patients with WDTC were identified. Ninety-two percent had PTC, while 7.7% had FTC. The average age was 48.4 years and OS was 96.3%, with a median follow-up of 52.7 months. When analyzing age in 5-year increments, 10-year mortality increased incrementally by 30-50% per age group for PTC, from age < 35 to ≥ 70 years, without an obvious inflection point. However, FTC patients experienced a more than threefold increase in 10-year mortality from age 40-44 years (2.5%) to age 45-49 years (7.9%). The same pattern was found on multivariable Cox regression. The Youden index found the optimal age thresholds were 58.5 years for PTC and 46.2 years for FTC.

CONCLUSION

OS for PTC decreases incrementally with age, but OS for FTC decreases significantly in patients aged 45 years and older. A higher age threshold may inappropriately downstage some high-risk follicular cancer patients.

Prognostic value of the 8th tumor-node-metastasis classification for follicular carcinoma and poorly differentiated carcinoma of the thyroid in Japan

Follicular thyroid carcinoma (FTC), a form of differentiated thyroid carcinoma, is the second most common malignancy arising from thyroid follicular cells. Recently, the tumor-node-metastasis (TNM) classification for differentiated thyroid carcinoma was revised from the 7^th to the 8^th edition. The diagnostic criteria for poorly differentiated carcinoma (PDC) were also updated in the latest World Health Organization (WHO) classification. In this study, we investigated whether these changes are appropriate for accurately predicting prognosis. Three hundred and twenty-nine patients diagnosed with postoperative pathologically confirmed FTC, who underwent initial surgery at our hospital between 1984 and 2004, were enrolled. For this study, patients were re-evaluated and diagnosed with FTC (N = 285) or PDC (N = 44) without typical nuclear findings of papillary thyroid carcinoma. For FTC, the 8^th TNM classification was a more accurate predictor of prognosis than the 7^th TNM classification. In the 8^th TNM classification, cause-specific survival became significantly poorer from Stage I to IVB. The cause-specific survival of PDC based on the latest WHO classification was worse than, but did not significantly differ from, that of PDC based only on the former WHO classification. For PDC, neither of the TNM classifications could accurately predict prognosis. Taken together, we conclude that (1) the 8^th TNM classification more accurately reflects the prognosis of FTC than the 7^th TNM classification; (2) PDC based on the former WHO classification should be retained, at least in Japan; and (3) the TNM classification may not be suitable for predicting the prognosis of PDC.

Follicular thyroid cancer and Hürthle cell carcinoma: challenges in diagnosis, treatment, and clinical management

Follicular thyroid cancer is the second most common differentiated thyroid cancer histological type and has been overshadowed by its more common counterpart-papillary thyroid cancer-despite its unique biological behaviour and less favourable outcomes. In this Review, we comprehensively review the literature on follicular thyroid cancer to provide an evidence-based guide to the management of these tumours, to highlight the lack of evidence behind guideline recommendations, and to identify changes and challenges over the past decades in diagnosis, prognosis, and treatment. We highlight that correct identification of cancer in indeterminate cytological samples is challenging and ultrasonographic features can be misleading. Despite certain unique aspects of follicular thyroid cancer presentation and prognosis, no specific recommendations exist for follicular thyroid cancer and Hürthle cell carcinoma in evidence-based guidelines. Efforts should be made to stimulate additional research in this field.

CIRCULATING TUMOR CELLS IN MINIMALLY INVASIVE FOLLICULAR THYROID CARCINOMA AND BENIGN THYROID TUMORS WITH A FOLLICULAR PATTERN: PILOT EXPERIENCE

Purpose

Minimally invasive follicular thyroid carcinomas (MIFCs) are uncommon; literature offers limited guidance on their natural history and management. Starting January 2015 we measured circulating tumor cells (CTCs) in patients with MIFC (n=22) or benign thyroid tumors with follicular features (n=4).

Methods

In a retrospective analysis, we assessed detectability of and serial changes in CTC, compared demographic/clinical differences between CTC-positive versus CTC-negative subgroups using Student's t-test, and examined correlations between CTC status and serum thyroglobulin using Spearman's test. CTCs were quantitated via immunomagnetic separation/microscopic inspection.

Results

Thirteen patients (50%: 12/22 MIFC, 1/4 benign tumor) were initially CTC-positive; 3 remained CTC-positive in ≥1 subsequent measurement. CTC-positive patients had larger tumors and more frequent multifocality and vascular invasion versus CTC-negative patients (n=13). However, no tested variable differed significantly between the subgroups. After 17.2±10.5 months, neither subgroup showed evidence of disease. Significant correlation was absent (p ≥ 0.263) between CTC and Tg negativity (r = 0.243; n=13 evaluable) or initial CTC positivity and Tg positivity (r = -0.418; n=9 evaluable).

Conclusions

In the studied settings, CTC measurement is feasible, has unclear clinical/outcome implications, but may provide different information versus thyroglobulin testing. Lengthier assessment is warranted in larger series.

Paediatric follicular thyroid carcinoma - indolent cancer with low prevalence of RAS mutations and absence of PAX8-PPARG fusion in a Japanese population

AIMS

Paediatric follicular thyroid carcinomas are uncommon, and their clinicopathological features and molecular profiles are still unknown. In the present study, we aimed to investigate the clinicopathological aspects of a large series of follicular thyroid carcinomas (FTCs) in paediatric patients and to analyse the point mutations in codons 12, 13 and 61 of NRAS, HRAS and KRAS genes and the rearrangements of PAX8-PPARG.

METHODS AND RESULTS

A total of 41 paediatric FTCs less than 21 years of age were enrolled into the present study. We used direct sequencing and reverse transcription-polymerase chain reaction (RT-PCR) to detect RAS mutations and PAX8-PPARG fusions, respectively. The paediatric FTCs were 6:1 in a female to male ratio, with a mean tumour size of 52.7 mm. Distant metastasis was found in one case at the time of presentation. During a median follow-up time of 69 months, two cases had lung metastasis and all patients were alive. Histologically, all cases were minimally invasive FTCs and varied in growth patterns: microfollicular (39%), follicular (14.6%), solid/trabecular (6%), oncocytic (4.9%) and mixed patterns (26.8%). The mean Ki67 index was 5.7% and it was not statistically different among the growth patterns. NRAS mutations were found in five cases (12.2%) and associated significantly with small tumour size (P = 0.014). PAX8-PPARG fusion was not detected in our series.

CONCLUSION

Paediatric FTCs are indolent in clinical course in spite of their large tumour size and have a distinct genetic background. RAS mutations and PAX8-PPARG fusions may not play major roles in the tumorigenesis of paediatric FTCs.

Evolution of the histologic classification of thyroid neoplasms and its impact on clinical management

The vast majority of low grade follicular cell derived thyroid carcinomas follows an indolent clinical course and is associated with very low mortality. Risk stratification using multiple clinical and pathologic characteristics has become the standard of care to guide appropriate management and avoid overtreatment. Over the past few decades, the field of thyroid pathology has witnessed several major changes that significantly impacted upon patients' care. These are: 1) The reclassification of non-invasive encapsulated follicular variant of papillary thyroid carcinoma as noninvasive follicular thyroid neoplasm with papillary-like nuclear features; 2) the diagnosis of Hurthle cell carcinoma based on the presence of capsular and vascular invasion; 3) a detailed definition of poorly differentiated thyroid carcinoma, taking into consideration mitosis and necrosis; and 4) the emphasis on a detailed pathologic analysis such as the extent of vascular invasion and extrathyroidal extension. This review describes these histological concepts and details the history, rationale, and clinical impacts of such changes. These shifts in the classification and characterization of thyroid carcinoma provided a platform supporting therapy de-escalation. In addition several lessons were learned from these changes especially from the misclassification of the non-invasive encapsulated follicular variant of papillary thyroid carcinoma. We hope that the lessons learned will help better classify tumors in the future whether arising in the thyroid or other organs.

Thick tumor capsule is a valuable risk factor for distant metastasis in follicular thyroid carcinoma

OBJECTIVE

While the biological behavior of follicular thyroid carcinoma (FTC) has been studied in great detail using clinical experience, few studies have investigated pre- or intraoperative factors related to the risk of distant metastasis (DM) among patients with FTC. The aim of this study was to analyze the characteristics of FTC with DM.

METHODS

This study retrospectively investigated 102 patients with FTC who underwent surgery between 1988 and 2013. We compared clinicopathological characteristics between FTC with and without DM.

RESULTS

Univariate analysis revealed nodal metastasis (p=0.045), serum thyroglobulin (Tg) at initial operation (≥1000ng/ml; p<0.0001), widely invasive appearance according to macroscopic findings (p<0.0001), thick tumor capsule (≥1mm; p<0.0001), vascular invasion (p=0.0003), extrathyroidal invasion (p=0.047), and venous tumor embolism (p=0.045) as significant risk factors for DM. Multivariate analysis conducted using pre- and intraoperative factors identified thick tumor capsule (≥1mm), serum Tg at initial operation (≥1000ng/ml), and macroscopically widely invasive appearance as risk factors independently associated with development of DM.

CONCLUSION

Patients with these risk factors should undergo total thyroidectomy and radioactive iodine ablation.

Prognostic impact of Ki-67 labeling index in minimally invasive follicular thyroid carcinoma

We investigated the prognostic impact of the Ki-67 labeling index (LI) in minimally invasive follicular thyroid carcinoma (FTC). We enrolled 192 patients (including four with distant metastasis at diagnosis) who were pathologically diagnosed as having minimally invasive FTC between 1998 and 2007 at Kuma Hospital. When the Ki-67 LI was higher than 5% in the hot area, we regarded it as a high Ki-67 LI. In a univariate analysis, patient age (≥45 years), high-frequent vascular invasion (≥4 in H&E specimens), and high Ki-67 LI significantly predicted the disease-free survival (DFS) of the patients. Since none of the patients <45 years old showed a recurrence, we performed a multivariate analysis of variables other than patient age. In the multivariate analysis including the presence of vascular invasion, high Ki-67 LI was an independent predictor of carcinoma recurrence. However, in the multivariate analysis including high-frequent vascular invasion, only high-frequent vascular invasion independently affected the DFS. These findings suggest that the Ki-67 LI has a rather strong prognostic value for the DFS of patients, although its impact was less than those of patient age and high-frequent vascular invasion.

Current dilemmas in the diagnosis and management of follicular thyroid tumors

Follicular carcinoma (FTC) is a relatively uncommon type of differentiated thyroid carcinoma. Guidelines have often dealt with FTC and papillary thyroid cancer as a single disease. Over the last decade, however, a better understanding of these two types of thyroid cancer indicates that they cannot be analysed together. Neither ultrasonography nor fine-needle aspiration cytology can provide a clear distinction between FTC and follicular adenoma. New molecular diagnostic techniques may be used to identify a subpopulation of follicular neoplasms with a low probability of being malignant. Diagnostic surgery-usually hemithyroidectomy- is recommended for most thyroid follicular lesions without a certain preoperative diagnosis. If FTC is diagnosed most-perhaps not all- patients will require a completion thyroidectomy. While widely invasive FTC usually does not pose diagnostic or therapeutic doubts, consensus on the diagnosis of non-invasive follicular lesions is still lacking. Prognosis of FTC is mostly dependent on local invasion and distant metastasis that, in turn, correlate with tumor size.

Risk Factors for Distant Metastasis in Patients with Minimally Invasive Follicular Thyroid Carcinoma

Background

Although patients with minimally invasive follicular thyroid carcinoma (MIFTC) generally have an excellent prognosis, distant metastasis occurs in some patients. Risk factors for distant metastasis have been reported, none has been found to be conclusive. This study evaluated risk factors for distant metastasis, including protein markers, in patients with MIFTC.

Methods

A review of patient records identified 259 patients who underwent surgery at Asan Medical Center from 1996 to 2010 and were subsequently diagnosed with MIFTC. After review of pathological slides, 120 patients with paraffin blocks suited for tissue microarrays (TMA) were included in this study. Immunohistochemical stain of TMA slides was performed by protein markers; β-catenin, C-MET, CK19, estrogen receptor (ER) α, ER β, HBME-1, MMP2, PPAR γ and progesterone receptor.

Results

120 patients included 28 males (23.3%) and 92 females (76.7%), of mean age 41.5±10.8 years (range, 13–74 years). Eight patients (6.7%) had distant metastases during follow-up. Univariate analysis showed that age (≥45 years), male sex, and extensive vascular invasion (≥4 foci) were associated with distant metastasis. Multivariate regression analysis showed that extensive vascular invasion was the only independent risk factor for distant metastasis (p = 0.012). Although no protein markers on TMA analysis were directly related to distant metastasis of MIFTC, CK19 expression was more frequent in patients with than without extensive vascular invasion (p = 0.036).

Conclusion

Extensive vascular invasion was the only independent risk factor for distant metastasis of MIFTC. No proteins markers were directly related to distant metastasis, but CK19 was associated with extensive vascular invasion.

Primary follicular thyroid carcinoma metastasis to the kidney and widespread dissemination: A case report

Distant metastases are more common in follicular thyroid carcinoma (FC) than in papillary thyroid carcinoma. However, FC metastasis to the kidney with eggshell calcification, as observed in the present case, is rare. The current report presents a case of a 67-year-old woman exhibiting a solitary tumor in the mid pole of the left kidney. Radical nephrectomy was performed, as the tumor was diagnosed as a primary renal carcinoma using contrast-enhanced computed tomography. Once the tumor was confirmed to be FC, total thyroidectomy was performed. Following administration of an oral therapeutic dose of 100 mCi ¹³¹I, functional imaging demonstrated the presence of multifocal metastases in the chest and abdomen. Euthyrox^® was prescribed orally to aid normal thyroid function. Follow-up 6 months later using radionuclide imaging demonstrated the disappearance of the multifocal metastases in the chest and abdomen. The distant metastasis of FC may represent the initial symptom of the primary lesion, which was neglected. Ultrasound is an effective method to examine nodules located on the thyroid.

Minimally invasive follicular carcinoma: predictors of vascular invasion and impact on patterns of care

Some studies have reported that minimally invasive follicular carcinoma (MIFC) with vascular invasion is associated with compromised prognosis, leading to an ongoing debate regarding extent of surgery for MIFC. Our goal was to identify predictors of vascular invasion and determine its impact on patterns of care. Adult patients with MIFC were culled from the National Cancer Database, 2010-2011, and segregated according to the presence/absence of capsular or vascular invasion. Variables of interest were examined using Chi-square and student's t tests. Multivariate analysis was performed with logistic regression. A total of 617 patients with MIFC were identified: 54% with capsular invasion only and 46% with vascular invasion. Demographic characteristics were similarly distributed between the two groups. Tumor size was larger in patients with vascular invasion (mean = 35.7 vs. 29.2 mm capsular invasion only, p < 0.001); a 2% increase in risk of vascular invasion was observed with each 1 mm increase in size. The rate of total thyroidectomy was similar for MIFCs with vascular invasion compared to capsular invasion only (72.9 vs. 75.1%, p = 0.537). The RAI administration rate was higher in patients with vascular invasion (62.1 vs. 52.6% capsular invasion only, p = 0.017). In multivariate analysis, the presence of vascular invasion was independently associated with increased likelihood of receiving RAI (OR 1.641, p = 0.007). MIFC remains aggressively treated despite current guidelines favoring a more conservative approach. Building consensus around MIFC management is important for standardization of practice patterns and improvement in quality of care.

Prognostic impact of extent of vascular invasion in low-grade encapsulated follicular cell-derived thyroid carcinomas: a clinicopathologic study of 276 cases

Continuous controversy surrounds the predictive value of the degree of vascular invasion (VI) in low-grade encapsulated follicular cell-derived thyroid carcinomas (LGEFCs). Some guidelines advocate conservative therapy in LGEFCs with focal VI. There is therefore a need to assess the survival rates of LGEFC patients with various degrees of VI to better stratify patients for subsequent therapy. Furthermore, the prognostic effect of VI within the different histotypes of LGEFCs is not well known. A total of 276 patients with LGEFCs were subjected to a meticulous histopathologic analysis. They were classified as encapsulated papillary thyroid carcinoma, encapsulated follicular carcinoma (EFC), and encapsulated Hurthle cell carcinoma (EHCC). Of the 276 patients, 24 had extensive VI (EVI) (≥4 foci) and 28 displayed focal (<4 foci) VI. EHCC and EFC showed a much higher rate of EVI than encapsulated papillary thyroid carcinoma. Median follow-up was 6 years. All 14 tumors with adverse behavior harbored distant metastases (DMs), of which 9 had DMs at presentation. All 3 patients without EVI who had aggressive carcinomas harbored DMs at presentation. EVI was an independent predictor of poor recurrence-free survival. Excluding cases with DMs at presentation, only patients with EVI had recurrence, and all relapsed cases were EHCC. EVI is an independent predictor of recurrence-free survival in LGEFCs. EHCC with EVI has a particularly high risk of recurrence. When DMs are not found at presentation, patients with focal VI are at a very low risk of recurrence even if not treated with radioactive iodine.

Revisiting the guidelines issued by the Japanese Society of Thyroid Surgeons and Japan Association of Endocrine Surgeons: a gradual move towards consensus between Japanese and western practice in the management of thyroid carcinoma

BACKGROUND

In 2010, the Japanese Society of Thyroid Surgeons (JSTS) and Japanese Association of Endocrine Surgeons (JAES) established new guidelines entitled "Treatment of Thyroid Tumors." Since then, several new studies, including those that address the treatment of differentiated thyroid carcinoma (DTC) have been published, and the DTC treatment policy not only of Japanese physicians but those in Western countries has continued to evolve.

METHODS

We selected six clinical questions regarding the treatment of DTC and revisited them based on newly published data from Western countries and Japan.

RESULTS

More data have accumulated about treatment of low-risk papillary microcarcinoma. It has become clear that conservative treatment (observation) of low-risk papillary microcarcinoma in elderly patients is an acceptable alternative to immediate surgery. Total thyroidectomy versus hemithyroidectomy for low-risk papillary thyroid carcinoma (PTC) has become an important issue, and some publications after 2010 indicated that hemithyroidectomy is adequate for these low-risk patients. Unfortunately, no published manuscripts on prophylactic central node dissection offered good evidence regarding its indications or included a large number of patients. Also, it was not evident that prophylactic lateral node dissection improves cause-specific survival, although it might reduce lymph node recurrence especially in PTC patients with large tumors, distant metastases, or clinical central node metastases. Although completion total thyroidectomy was not recommended for minimally invasive follicular thyroid carcinoma in our guidelines, it may be better to perform it in elderly patients and those with a large tumor or extensive vascular invasion. Radioactive iodine (RAI) ablation after total thyroidectomy is still performed almost routinely in many Western institutions, although recent studies showed that ablation is not beneficial in low-risk patients. In Japan, because of legal restrictions, most patients did not undergo RAI ablation, and their prognoses are excellent.

CONCLUSIONS

Recently, policy for treating DTCs has changed not only in Western countries but also in Japan, resulting in a gradual move toward consensus between Western practice and ours. We will continue to present the best treatments for patients with thyroid carcinoma each time we revise our guidelines.

[Clinical guideline for management of patients with low risk differentiated thyroid carcinoma]

Incidence of thyroid cancer is increasing in Spain and worldwide. Overall thyroid cancer survival is very high, and stratification systems to reliably identify patients with worse prognosis have been developed. However, marked differences exist between the different specialists in clinical management of low-risk patients with thyroid carcinoma. Almost half of all papillary thyroid carcinomas are microcarcinomas, and 90% are tumors < 2 cm that have a particularly good prognosis. However, they are usually treated more aggressively than needed, despite the lack of adequate scientific support. Surgery remains the gold standard treatment for these tumors. However, lobectomy may be adequate in most patients, without the need for total thyroidectomy. Similarly, prophylactic lymph node dissection of the central compartment is not required in most cases. This more conservative approach prevents postoperative complications such as hypoparathyroidism or recurrent laryngeal nerve injury. Postoperative radioiodine remnant ablation and strict suppression of serum thyrotropin, although effective for the more aggressive forms of thyroid cancer, have not been shown to be beneficial for the treatment of low risk patients, and may impair their quality of life. This guideline provides recommendations from the task force on thyroid cancer of the Spanish Society of Endocrinology and Nutrition for adequate management of patients with low-risk thyroid cancer.

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.