Encapsulated columnar-cell neoplasms of the thyroid. A report of four cases suggesting a favorable prognosis

Overview of the 2022 WHO Classification of Thyroid Neoplasms

This review summarizes the changes in the 5th edition of the WHO Classification of Endocrine and Neuroendocrine Tumors that relate to the thyroid gland. The new classification has divided thyroid tumors into several new categories that allow for a clearer understanding of the cell of origin, pathologic features (cytopathology and histopathology), molecular classification, and biological behavior. Follicular cell-derived tumors constitute the majority of thyroid neoplasms. In this new classification, they are divided into benign, low-risk, and malignant neoplasms. Benign tumors include not only follicular adenoma but also variants of adenoma that are of diagnostic and clinical significance, including the ones with papillary architecture, which are often hyperfunctional and oncocytic adenomas. For the first time, there is a detailed account of the multifocal hyperplastic/neoplastic lesions that commonly occur in the clinical setting of multinodular goiter; the term thyroid follicular nodular disease (FND) achieved consensus as the best to describe this enigmatic entity. Low-risk follicular cell-derived neoplasms include non-invasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP), thyroid tumors of uncertain malignant potential, and hyalinizing trabecular tumor. Malignant follicular cell-derived neoplasms are stratified based on molecular profiles and aggressiveness. Papillary thyroid carcinomas (PTCs), with many morphological subtypes, represent the BRAF-like malignancies, whereas invasive encapsulated follicular variant PTC and follicular thyroid carcinoma represent the RAS-like malignancies. This new classification requires detailed subtyping of papillary microcarcinomas similar to their counterparts that exceed 1.0 cm and recommends not designating them as a subtype of PTC. The criteria of the tall cell subtype of PTC have been revisited. Cribriform-morular thyroid carcinoma is no longer classified as a subtype of PTC. The term "Hürthle cell" is discouraged, since it is a misnomer. Oncocytic carcinoma is discussed as a distinct entity with the clear recognition that it refers to oncocytic follicular cell-derived neoplasms (composed of > 75% oncocytic cells) that lack characteristic nuclear features of PTC (those would be oncocytic PTCs) and high-grade features (necrosis and ≥ 5 mitoses per 2 mm²). High-grade follicular cell-derived malignancies now include both the traditional poorly differentiated carcinoma as well as high-grade differentiated thyroid carcinomas, since both are characterized by increased mitotic activity and tumor necrosis without anaplastic histology and clinically behave in a similar manner. Anaplastic thyroid carcinoma remains the most undifferentiated form; squamous cell carcinoma of the thyroid is now considered as a subtype of anaplastic carcinoma. Medullary thyroid carcinomas derived from thyroid C cells retain their distinct section, and there is a separate section for mixed tumors composed of both C cells and any follicular cell-derived malignancy. A grading system for medullary thyroid carcinomas is also introduced based on mitotic count, tumor necrosis, and Ki67 labeling index. A number of unusual neoplasms that occur in the thyroid have been placed into new sections based on their cytogenesis. Mucoepidermoid carcinoma and secretory carcinoma of the salivary gland type are now included in one section classified as "salivary gland-type carcinomas of the thyroid." Thymomas, thymic carcinomas and spindle epithelial tumor with thymus-like elements are classified as "thymic tumors within the thyroid." There remain several tumors whose cell lineage is unclear, and they are listed as such; these include sclerosing mucoepidermoid carcinoma with eosinophilia and cribriform-morular thyroid carcinoma. Another important addition is thyroblastoma, an unusual embryonal tumor associated with DICER1 mutations. As in all the WHO books in the 5th edition, mesenchymal and stromal tumors, hematolymphoid neoplasms, germ cell tumors, and metastatic malignancies are discussed separately. The current classification also emphasizes the value of biomarkers that may aid diagnosis and provide prognostic information.

Genomic profile of columnar cell variant of papillary thyroid carcinoma

BACKGROUND AND AIMS

Columnar cell variant (CCV) is a rare papillary thyroid carcinoma subtype. The majority of CCV occur in older patients and are large, invasive tumours that pursue an aggressive clinical course. Rare well-circumscribed CCV occur in younger female patients and are comparatively indolent.

METHODS AND RESULTS

We retrospectively identified CCV with material available to perform targeted next-generation sequencing and correlated molecular results with clinicopathological features and outcome. Our cohort was comprised of nine CCV. Nearly all were aggressive tumours; however, one was predominantly well-circumscribed and arose in a thyroglossal duct cyst of a 26-year-old woman who had no evidence of disease at last follow-up. Seven (78%) cases demonstrated activating oncogenic driver alterations in BRAF, including BRAF V600E, an activating N486_P490del deletion, and BRAF-AGK fusions. Activating RAS mutations were seen in two (22%) cases. Additionally, three (33%) cases had TERT promoter mutations, four (44%) had loss of the tumour suppressor CDKN2A and one (11%) case had a loss of function TP53 mutation. Most cases (89%) also demonstrated copy number alterations, including recurrent gain of chromosome 1q (five cases) and losses of chromosome 9p (three cases) and 22q (four cases). The one case without secondary pathogenic mutations or copy number alterations was the tumour in the 26-year-old woman.

CONCLUSIONS

We found that CCV is primarily a BRAF-driven tumour, with most also harbouring secondary oncogenic mutations and multiple chromosomal gains and losses. Moreover, our findings suggest that molecular analysis could potentially be used to help risk stratify CCV.

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.

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.

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.

Columnar Cell Variant of Papillary Thyroid Carcinoma: Ultrasonographic and Clinical Differentiation between the Indolent and Aggressive Types

Objective

To evaluate the ultrasonography (US) features and clinical characteristics of columnar cell variant of papillary thyroid carcinoma (CCV-PTC) that can predict disease progression.

Materials and Methods

Six cases of CCV-PTC were identified via surgical pathology analysis at our institution from 1994 to 2016. The histological, architectural, and cytological features met the diagnostic criteria of CCV-PTC. We reviewed the US features and clinicopathological findings in the six cases.

Results

An indolent clinical course was observed in four young female patients aged 27–34 years (median: 32 years), while two older patients aged 55 years or 70 years had an aggressive clinical course. All patients underwent total thyroidectomy and radioiodine therapy. The indolent group included patients with T1 and nodal metastasis, where the disease was not observed during the follow-up period (range: 8–17 years). On the other hand, a larger tumor size (1.8 cm and 6.0 cm), gross extrathyroidal extension to the muscle and lymph node, and distant metastasis were observed in the aggressive group. In one male patient, recurrence occurred immediately after operation, and this patient died 4 years after the diagnosis of thyroid cancer. Based on US, the individuals from the indolent group had a smooth margin, except for one. Both cases in the aggressive group had a microlobulated margin.

Conclusion

Favorable prognosis in CCV-PTC is observed in young patients with T1 staging and demonstrates a smooth margin at US. These US findings might help exclude the same treatment as the aggressive type in the indolent type of CCV-PTC.

Defining Papillary Carcinoma of the Thyroid: A Short Review and Analysis

OBJECTIVES

To review how changes in the pathologic definitions for papillary tumors of the thyroid during recent decades have affected outcomes for patients with these tumors.

METHODS

Forty-nine previous reports or studies involving collectively 53,606 patients were reviewed, and new analyses were performed on the data to include analyses of agreement, incidence, survival, and diagnostic categories.

RESULTS

The past emphasis on cytologic features to define papillary tumors has not resulted in ideal pairwise agreement between pathologists and has produced incidence and survival data suggesting overdetection and overdiagnosis. Most recently, tissue patterns have been reemphasized.

CONCLUSIONS

With the recent reemphasis on diagnostic tissue patterns (over cytologic criteria), agreements between pathologists for the diagnosis of papillary tumors should improve, and the incidence of papillary carcinoma should decline. Nevertheless, updated survival analyses demonstrate excellent long-term survival for most of those diagnosed with papillary carcinomas.

Update on the cytologic features of papillary thyroid carcinoma variants

Papillary thyroid cancer (PTC), which accounts for 85-90% of all thyroid cancers, is generally an indolent tumor with long term survival rates >95%. A reliable definitive diagnosis of PTC is usually straightforward in fine needle aspirates of conventional PTC whenever the characteristic papillary and/or flat honeycomb sheet-like architecture and the typical nuclear features of chromatin pallor, nuclear enlargement, crowding, grooves and pseudoinclusions are encountered. Conventional PTC, however, has diminished in relative frequency as compared to PTC variants, especially the noninvasive follicular variant of PTC, an indolent tumor which has recently been reclassified as "noninvasive follicular thyroid neoplasm with papillary-like nuclear features" (NIFTP). These PTC variants are characterized by various architecture, cell type and shape, and stromal features, some of which can be recognized cytologically. Awareness of the cytomorphological spectrum and of the characteristic cytological features of these PTC variants is important to avoid diagnostic pitfalls. In this article, we review the different variants of PTC, including their cytomorphologic features, differential diagnosis, and salient molecular features. Diagn. Cytopathol. 2017;45:714-730. © 2017 Wiley Periodicals, Inc.

Prognostic indicators for papillary thyroid carcinoma

Differentiated thyroid cancer (DTC) includes more than 90% of all thyroid carcinoma and its incidence is growing, mainly due to an increase in the incidence of papillary thyroid cancer (PTC) for the widespread use of neck ultrasonography. Areas covered: Several prognostic factors should be considered during the management of PTC in order to provide the most effective treatment. The most important prognostic factors in PTC include personal and pathological features such as patient's age, gender, hystotype, tumor size, extrathyroidal extension, lymph node involvement, presence of local or distant metastases and molecular analyses. We performed a search in the PubMed database for studies published in English since 1960 using the terms: 'thyroid cancer', 'prognostic factors', 'age', 'gender', 'hystotype', 'tumor size', 'extrathyroidal extension', 'lymph node', 'metastases' and 'molecular analyses'. Expert commentary: Prognostic factors can guide clinicians during the treatment and follow-up of DTC patients, but it is now evident that the risk of recurrence or death must be evaluated periodically, on the basis of individual risk, according to the response to initial therapy or the subsequent therapy required during follow-up.

Ultrasonographic imaging of papillary thyroid carcinoma variants

Ultrasonography (US) is routinely used to evaluate thyroid nodules. The US features of papillary thyroid carcinoma (PTC), the most common thyroid malignancy, include hypoechogenicity, spiculated/microlobulated margins, microcalcifications, and a nonparallel orientation. However, many PTC variants have been identified, some of which differ from the classic type of PTC in terms of biological behavior and clinical outcomes. This review describes the US features and clinical implications of the variants of PTC. With the introduction of active surveillance replacing immediate biopsy or surgical treatment of indolent, small PTCs, an understanding of the US characteristics of PTC variants will facilitate the individualized management of patients with PTC.

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.

Sonographic and cytopathologic correlation of papillary thyroid carcinoma variants

Papillary thyroid carcinoma (PTC) is the most common thyroid cancer and constitutes more than 70% of thyroid malignancies. Although TNM staging is the most widely used parameter for determination of therapeutic plans, recent studies have suggested that different histopathologic variants of PTC can also have different clinical courses and patient prognoses. Sonographic criteria for PTC are well established and include a taller-than-wide shape, an irregular margin, microcalcifications, and marked hypoechogenicity. The role of sonography has expanded to enable the characterization of PTC variants based on their sonographic features. Tall cell and diffuse sclerosing variants appear to have more aggressive clinical courses with unfavorable prognoses, whereas the more recently described cribriform-morular and Warthin-like variants have relatively indolent clinical courses. The prognoses of patients with follicular, solid, columnar cell, and oncocytic variants are still controversial and may be similar to the prognosis of conventional PTC. Understanding the sonographic characteristics of PTC variants with clinicopathologic correlation may be helpful for suggesting an appropriate treatment plan.

Cytomorphology of columnar cell variant of papillary carcinoma thyroid: A case report and review of the literature

A 58 years old lady reported with history of progressively increasing lump in the neck. Patient had earlier undergone sub-total thyroidectomy (details not available) in a private institute one year back. Fine needle aspiration cytology (FNAC) of the present lump revealed features of papillary carcinoma thyroid. Patient subsequently underwent total thyroidectomy along with excision of a tumor nodule in the larynx. Gross examination of the specimen revealed a tumor nodule in the right lobe of the thyroid. Microscopic examination of the tumor nodule in the thyroid and larynx revealed a columnar cell variant of papillary carcinoma thyroid. Very few reports describing the cytomorphologic features of this variant of papillary carcinoma are available in the published literature. These reports highlight the absence or paucity of nuclear grooves and intranuclear inclusions in this variant. We describe a case of columnar cell variant of papillary carcinoma where nuclear grooves were prominently seen. In addition, we report the occurrence of rosette-like structures which were brought out better on FNA smears. These rosette-like structures have not been emphasized earlier in the published literature. The cytomorphologic features of this rare variant are also reviewed in this report.

Noninvasive anaplastic thyroid carcinoma: report of a case and literature review

Anaplastic thyroid carcinoma (ATC) is an uncommon thyroid malignancy. Noninvasive ATC is a rare, surgically resectable variant with only four reported cases. We report a case of an 81-year-old man who presented with a 3.1 cm right thyroid lobe mass that on fine-needle aspiration biopsy was diagnosed as an ATC. Preoperative imaging revealed an encapsulated thyroid tumor without evidence of invasion of surrounding structures and no locoregional and distant metastases. A total thyroidectomy was performed that by histologic and immunohistochemical evaluation was diagnostic for a noninvasive ATC. Given the diagnosis of noninvasive ATC, adjuvant therapy was not administered. At 14 months following diagnosis, the patient remains disease free based on positron emission tomography/computed tomography imaging. A review of the outcomes of similar cases reported in the literature, as well as observations from our case, suggest a favorable prognosis for patients with noninvasive ATC. Noninvasive ATC may represent a distinct subset of resectable ATCs with an improved prognosis. The recently published American Thyroid Association (ATA) Guidelines for Management of Patients with ATC do not include this specific form of ATC. We encourage other authors to report similar cases in order to determine whether noninvasive ATC should be considered as a separate disease entity from the traditional highly lethal form of ATC.

Aggressive variants of follicular cell-derived thyroid carcinomas: a cytopathologist's perspective

Follicular cell-derived carcinomas of the thyroid gland comprise a heterogeneous group of malignant neoplasms of the thyroid gland with varied histologic appearance and molecular profiles. In most patients, these tumors represent relatively indolent neoplasms; however, certain subtypes/variants behave in an aggressive manner, and the recognition of this subset of tumors is essential because of their variable response to therapy and significant morbidity and mortality. Fine-needle aspiration is considered an essential tool for the diagnosis of suspicious thyroid nodules. In this review, the authors discuss the clinical, histologic, and molecular findings and the prognostic implications of aggressive thyroid neoplasms with emphasis on the characteristic cytomorphologic features on fine-needle aspiration smears.

Follicular-patterned afflictions of the thyroid gland: reappraisal of the most discussed entity in endocrine pathology

The past 25 years has seen a marked increase in our understanding of thyroid neoplasia, from the interrelationship with radiation exposure, the definition of variants of papillary carcinoma, to the application of molecular biology techniques to capture a more basic definition of tumor development, diagnosis, and prognostic implications. No other group of thyroid tumors has been studied as much as those with follicular pattern. In this review, we present a reappraisal of these controversial lesions in light of the issues with the diagnostic problems and classification schemes of follicular thyroid lesions, with emphasis on the progress made in the past quarter century and a focus on the current persistent controversies.

Pathologic diagnosis of papillary thyroid carcinoma: today and tomorrow

Papillary thyroid carcinoma is the most common malignancy of the thyroid. It is a well-differentiated tumor and the majority behaves in an indolent fashion. The pathologic diagnosis of papillary carcinoma in both cytology and histologic specimens is based upon demonstration of typical nuclear morphology. Using these morphologic criteria, most papillary cancers can be diagnosed with ease, except cases in which there is a paucity of diagnostic nuclear features. Despite advances in the treatment of thyroid cancer, disease recurrences and metastasis can be observed in 20% of cases. Recently, many advances have been made in the pathogenesis of papillary thyroid carcinoma. The notable genetic events include Ret/PTC rearrangements, Ras and BRAF gene mutations. The identification of these has also led to their use in diagnosis and predicting prognosis of papillary thyroid carcinoma. In addition, these involved genes may also serve as targets for cancer chemotherapy in patients where standard thyroid cancer treatment is not effective.

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

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

Follicular-patterned tumors of the thyroid: the battle of benign vs. malignant vs. so-called uncertain

This article will review the controversial area of follicular-patterned thyroid tumors. The literature is discussed with emphasis on pathologic diagnosis and the criteria for malignancy. In addition, the current state of knowledge regarding molecular markers and their utility in diagnosing benign from malignant nodules is described. Finally, the apparent lack of consistency with regard to results of certain immunohistochemical markers is included.

Clinicopathological and molecular characterization of nine cases of columnar cell variant of papillary thyroid carcinoma

The majority of papillary thyroid carcinoma is indolent and associated with long-term survival. The columnar cell variant, however, is a rare subtype that is variable in biological behavior; some are clinically aggressive, whereas others are more clinically indolent. Tumor size, tumor circumscription, and encapsulation may influence the behavior of columnar cell carcinomas. Other variables including genetic changes and putative biomarkers associated with malignant growth have not been thoroughly examined in these neoplasms. In this study, nine cases of columnar cell variant of papillary thyroid carcinoma from three institutions were classified as clinically indolent or aggressive based on pathological features, clinical history, and outcome. Indolent tumors were typically small, circumscribed or encapsulated, and from younger female patients, whereas aggressive tumors were large, locally aggressive, associated with regional and distant metastasis, and from older male patients. The missense mutation, V600E in the BRAF oncogene (BRAF(V600E)), was detected in three of nine of cases, of which two were clinically aggressive. Immunohistochemical evaluation of neoplasia-associated markers showed increased nuclear cyclin D1 expression, elevated Ki-67 proliferation indices, and predominantly weak nuclear p53 staining in both indolent and aggressive tumors. Expression of β-catenin was largely restricted to a membranous pattern in both tumor types. Cytoplasmic expression of bcl-2 was overall mildly reduced in indolent neoplasms. Nuclear expression of estrogen and progesterone receptors was increased in both indolent and aggressive neoplasms, but was without sex- or age-related differences; however, whereas progesterone receptor expression was diffuse and strong in clinically indolent carcinomas, its expression was diminished in aggressive neoplasms. Recognition of the clinicopathological characteristics and the molecular and immunophenotypic features of the columnar cell variant of papillary thyroid carcinoma may aid in characterizing neoplasms that behave indolently or aggressively.

Cribriform-morular variant of papillary thyroid carcinoma: molecular characterization of a case with neuroendocrine differentiation and aggressive behavior

We describe an especially aggressive case of cribriform-morular variant (C-MV) of papillary thyroid carcinoma (PTC) in a 42-year-old man with familial adenomatous polyposis who died with lung and brain metastases 17 months after thyroidectomy. The angioinvasive neoplasm combined a mixture of trabecular, solid, cribriform, and follicular patterns of growth with CD10+ morules. Follicles were devoid of colloid, and the nuclear features typical of PTC were present in some areas and missing in others. Tumor cells were positive for thyroid transcription factor-1 and, in 40% of the tumoral mass, also were positive for chromogranin and synaptophysin and were negative for thyroglobulin and calcitonin. Strong nuclear staining for beta-catenin was found in all tumor cells, as was positivity for p53 and cyclin D1. In addition to the germline heterozygous APC Ex 2-3 duplication mutation, a somatic homozygous silent p. Thr1493Thr gene variant was found in the neoplastic cells along with RET/PTC rearrangement. This tumor represents the first case of C-MV of PTC showing neuroendocrine differentiation.

Subclassification of non-solid-type papillary thyroid carcinoma identification of high-risk group in common type

Two hundred and sixty-three cases of primary human papillary thyroid carcinoma (PTC) were analyzed. All cases met the following parameters: tumor size > or = 10 mm, no distant metastasis at presentation, and no coexistence of other histological type. The histological features of the solid/trabecular component, encapsulation, tall/columnar cell component and loss of polarity/cohesiveness were utilized to subclassify the 263 cases of PTC into five groups: solid type (15.6%), encapsulated group (9.5%), tall/columnar cell group (7.2%), micropapillary/discohesive group (19.8%) and not-otherwise-specified group (47.9%). We focused on the latter four non-solid groups and compared their prognosis with the solid type. The tall/columnar cell group showed the worst disease-free survival rate (DFS) analyzed by the Kaplan-Meier method, followed by the micropapillary/discohesive group. The not-otherwise-specified group and encapsulated group showed a better DFS rate than the solid type. Cancer-related death was noted in the tall/columnar cell group (21.1%) and micropapillary/discohesive group (3.8%), but not in the other groups. The four non-solid histological groups were further categorized into two prognostic groups: high-risk group (including tall/columnar cell group and micropapillary/discohesive group); and low-risk group (including encapsulated group and not-otherwise-specified group). Their 10-year disease-free survival rates were 78.7% and 93.1%, respectively. In the present study, histological grouping was significantly correlated with prognosis in the multivariate analysis according to the Cox proportional hazards regression model in addition to clinical parameters of extrathyroid invasion and gross lymph node metastasis, which predicts the patient outcome in terms of tumor recurrence and cancer-related death more precisely.

Unusual tumors of the thyroid gland

Thyroid neoplasms are classified into three major categories: epithelial, nonepithelial, and secondary. Most primary epithelial tumors of thyroid are derived from follicular cells. These include follicular adenoma and carcinoma (Hürthle and non-Hürthle), and papillary carcinoma and its variants. Other primary epithelial tumors include medullary carcinoma, mixed medullary and follicular carcinomas, insular and poorly differentiated carcinoma, anaplastic carcinoma, and the least common squamous carcinoma and related tumors. The nonepithelial tumors are rare; the most common include malignant lymphoma and tumors arising from the mesenchymal elements. The secondary tumors represent metastatic tumors to the thyroid usually originating in lung, kidney, and breast. In this article, the authors review the unusual tumors of the thyroid, their morphologic features, and clinical and prognostic implications.

Special Variants of Differentiated Thyroid Cancer: Does It Alter the Extent of Surgery Versus Well-Differentiated Thyroid Cancer?

INTRODUCTION

Recently, more aggressive variants of so-called well-differentiated thyroid carcinomas have been identified such as the tall cell variant, columnar cell variant, diffuse sclerosing variant, insular carcinoma, and Hürthle cell (oncocytic, oxyphilic) carcinomas.

METHODS

An evidence-based review was performed to identify the optimal treatment recommendations for these thyroid cancers of intermediate differentiation.

CONCLUSIONS

Although some variation exists within the group, aggressive surgical and medical management are recommended for these neoplasias. Any such recommendations should, however, be viewed in the light of the fact that the current literature mainly consists of case reports, case series, and limited reviews. The clinical presentation, pathophysiology, diagnosis, and surgical and medical management for these thyroid cancers with intermediate differentiation are discussed.

Prevalence and prognostic significance of tall cell variant of papillary thyroid carcinoma

The aim of this study was to assess the prevalence, prognostic factors, and long-term outcome of tall cell variant (TCV) in comparison with the conventional forms of papillary thyroid carcinoma (PTC). A total of 945 patients with thyroid cancer were treated and followed up from 1960 to 1998. Pathologic review was performed in 778 patients (84%) of the cohort. Of these, 674 had PTC: 503 (74%) had conventional form (CF); 56 (8%), TCV; and 155 (17%), other variants of PTC. Tall cell variant was associated with tumors of larger size (P < .001), bilaterality (P < .02), multifocality (P < .04), and extrathyroidal invasion (P < .001). Treatment was similar in both groups, but neck dissection was performed more frequently in patients with TCV (P < .04). The 10-year overall and event-free survival rates were, respectively, 90% and 85% in the CF versus 79% and 67% in the TCV group (P < .001). Histologic subtype did not have an effect on clinical outcome after multivariate analysis, the most relevant factors being age, involved nodes, or the "Metastasis, Age, Completeness, Invasion, Size" classification after multivariate analysis. In this large cohort of patients, TCV represents 8.3% of PTC, and it is a more aggressive form of PTC than CF because of the higher stage and increased grade.

Encapsulated Columnar-cell Carcinoma of the Thyroid: A Case Report

Columnar-cell carcinoma is a rare form of papillary thyroid carcinoma. It is a biologically aggressive variant, according to the World Health Organization classification, due to its rapid growth, high local recurrence rate, and frequent lung, brain, and bone metastases. However, recent reports indicate encapsulated tumors confined to the thyroid gland are associated with a more favorable prognosis. We report a case of encapsulated columnar-cell carcinoma occurring in the right lobe of the thyroid in a 25-year-old female and discuss the histopathologic features, differential diagnosis, and prognostic factors.

A review of thyroid cancer with intermediate differentiation

BACKGROUND AND OBJECTIVES

Tall cell (TCV), columnar cell (CCV), insular (IC), diffuse sclerosing (DSPTC) and solid/trabecular are uncommon subtypes of thyroid cancer, which have generally been described in case reports or small series in the world literature. Due to the rarity of these thyroid cancers, their clinical behavior remains incompletely understood. The aim of this review was to pool the currently available clinical information regarding these uncommon thyroid cancers so as to gain a better understanding of their clinical aspects and natural history.

METHODS

A computer-aided search of MEDLINE (1966-2001, PUBMED website) and CINAHL (1982-2001) databases was performed, as well as a review of the reference section of each primary study was done. All cases of TCV, CCV, DSPTC, solid/trabecular, and IC described in the English medical literature were identified. For the subtypes DSPTC, TCV, and IC, clinical data from the published case series were combined in a weighted analysis. Weighting was based on the number of cases per series. For the CCV and the solid/trabecular variant, due to the small number of cases, raw figures for the clinical features were obtained.

RESULTS

DSPTC (n = 65) appeared to have a tendency for intra-thyroidal extension (40%) and a high propensity for nodal metastates (68%). The mean overall tumor related mortality was similar to well differentiated thyroid cancer (WDTC) at only 2% at 8 years follow-up. The solid/trabecular variant was seen in 37% of the radiation induced thyroid tumors of the Chernobyl accident. It had a high propensity for extrathyroidal extension, and cervical lymph node metastases were found in up to 83% of patients. Unlike WDTC, TCV (n = 209) was a more aggressive tumor, associated with distant metastases in 22% of cases and had a mean tumor related mortality of 16%. The histological diagnosis of TCV was a poor prognostic factor regardless of patient age or tumor size. The CCV (n = 41) had a high overall mortality rate of 32%. When encapsulated, however, CCV had an excellent prognosis similar to that found in WDTC. In contrast, CCV tumors that were not encapsulated had extrathyroidal spread in 67% and had distant metastases in 87% of patients. The variant of IC (n = 213) appeared to be an aggressive subtype of thyroid cancer. The mean loco-regional recurrence and/or distant metastases rate was 64% and tumor related mortality was high at 32%.

CONCLUSIONS

DSPTC, TCV, CCV, and IC are thyroid cancer subtypes, which have a biological aggressiveness, which appear to be intermediate between that of WDTC and poorly differentiated anaplastic thyroid cancer. J. Surg. Oncol. 2004;86:44-54.

A mechanical model of tumor encapsulation and transcapsular spread

In this paper, a mathematical modeling framework is presented which describes the growth, encapsulation, and transcapsular spread of solid tumors. The model is based on the physical forces and cellular interactions involved in tumorigenesis and is used to test and compare the active (foreign body hypothesis) and passive (expansive growth hypothesis) hypotheses of capsule formation, such investigations being ideally suited to our mechanical model. The model simulations lead us to predict that, although an active response can successfully control tumor growth via the deposition of large amounts of collagen, this alone is insufficient for capsule formation. In contrast, a solely passive responsive is capable of producing an encapsulated tumor with minimal accumulation of connective tissue within the tumor. When both responses are active, a denser capsule forms and there is a significant increase in connective tissue within the tumor. Using a modified version of the model, in which tumor cells are assumed to produce degradative proteases at a rate which depends on the pressure they experience, it is also possible to show that transcapsular spread or invasion of the tumor may be due to the production by the tumor cells of proteases and their subsequent action.

Columnar-cell carcinoma of the thyroid

A case of columnar-cell carcinoma of the thyroid gland occurring in a 77-year-old female is described. Tracheal deviation and calcified anterior neck lesion were showed in X-ray examination. A computed tomography (CT) scan revealed a soft tissue density mass with calcification of the right thyroid lobe and isthmus. A (99m)Tc scintiscan showed a 'cold' nodule, whereas a (201)Tl scintiscan showed a 'hot' in the right thyroid lobe and isthmus. Subtotal thyroidectomy and dissection of paratracheal adipose tissue were performed after fine needle aspiration cytology (FNA) of the thyroid mass had been done. On the FNA smears, there were many papillary fragments, which contained pseudostratified columnar cells. Histopathologically, the tumor had three different types of neoplasm including papillary carcinoma of usual feature, columnar-cell carcinoma and follicular carcinoma. Transitional changes were observed between columnar-cell carcinoma and follicular carcinoma. The patient has been followed up for 3 years, with no evidence of recurrence or metastasis.

Prognostic factors in well-differentiated follicular-derived carcinoma and medullary thyroid carcinoma

This paper reviews both clinicopathologic and biological factors in differentiated thyroid carcinoma of follicular and C-cell derivation. The value of specific histological parameters including tumor subtypes, vascular invasion as predictors of prognosis in these tumors is discussed and the pertinent literature reviewed. The utility of ploidy analysis and immunohistochemical assessment of hormonal and tumor markers are described. Current information on biological and molecular markers that may be helpful in predicting behavior is discussed. The commonly used staging systems for thyroid cancer are briefly described.

Poorly differentiated follicular thyroid carcinoma with rhabdoid phenotype: a clinicopathologic, immunohistochemical and electron microscopic study of two cases

Poorly differentiated thyroid carcinomas with follicular cell phenotype are not well defined. Different diagnostic criteria have been employed for these tumors, including solid growth, nodular, trabecular, and insular patterns. Cytologic features, such as a predominance of tall and columnar cells, have been considered to be diagnostic of poorly differentiated carcinoma. However, there is no agreement among surgical pathologists regarding morphologic criteria for poorly differentiated thyroid carcinoma. We report two unique thyroid neoplasms that we interpreted as poorly differentiated follicular carcinomas. Nodular, trabecular, and sheetlike patterns predominated in both tumors. They were composed of cells that were focally immunoreactive for thyroglobulin and had large vesicular nuclei with prominent nucleoli. A variable number of cells showed rhabdoid phenotype. The rhabdoid inclusions did not stain for thyroglobulin but contained whorls of intermediate filaments that were vimentin positive. There were foci of necrosis and numerous mitotic figures. Both patients were adults and died with multiple pulmonary metastases. The presence of rhabdoid cells in poorly differentiated follicular carcinomas broadens the spectrum of tumors with rhabdoid phenotype. More cases are needed to determine whether the rhabdoid phenotype is a marker for poorly differentiated follicular carcinoma as well as an independent adverse prognostic factor.

The importance of a tumor capsule in columnar cell thyroid carcinoma: a report of two cases and review of the literature

Two cases of papillary columnar cell thyroid carcinoma are presented. A 49-year-old man presented with lymph node and pulmonary metastases at diagnosis; a 51-year-old woman developed local recurrence and lung and bone metastases 3 years postsurgery. Death occurred after 52 and 57 months, respectively. The first case lacked a tumor capsule, although the second exhibited capsule remains with extensive tumor cell infiltration. A review is made of all similar cases reported to date in the literature, placing emphasis on the epidemiological and prognostic differences observed in terms of circumscribed or noncircumscribed tumor. The presence of a capsule was associated with a higher frequency of female patients and a favorable prognosis. In contrast, tumors profusely infiltrating the thyroid parenchyma or extrathyroid tissues in the absence of a capsule, found in similar proportion of men and women had a fatal prognosis.

Fine-needle aspiration cytology of columnar-cell carcinoma of the thyroid: report of two cases with cytohistologic correlation

The columnar-cell variant of papillary carcinoma is a rare tumor of the thyroid, associated with aggressive behavior, early visceral metastasis, and a rapidly fatal course. In this report we present the fine-needle aspiration cytologic findings of two examples of this variant of papillary carcinoma with cytohistologic correlation. In the smears, clusters, monolayered sheets, and scattered papillary fronds of tumor cells were present. The tumor cells were columnar and exhibited overlapping and stratification of the nuclei. In the first case the tumoral cells showed round nuclei with finely granular chromatin pattern, small nucleoli and vacuolated-appearing cytoplasm. The malignant cells in the second case presented oval to elongated nuclei with stippled chromatin, inconspicuous nucleoli and indistinct cytoplasmic borders. It is important to distinguish this tumor from the common thyroid papillary carcinoma because of its much more aggressive behavior.

Columnar Cell Carcinoma of the Thyroid: MIB-1 Immunoreactivity as a Prognostic Factor

We report a case of columnar cell carcinoma of the thyroid. A 47-year-old Japanese man had a nonencapsulated thyroid mass that infiltrated the surrounding tissues extensively. Seventeen months after thyroidectomy he died of respiratory failure resulting from tracheal invasion. An autopsy showed distant metastases to the liver, lung, esophagus, and pancreas. Histologically, the thyroid mass consisted of tall columnar atypical cells with marked nuclear stratification, About one-fifth of tumor cells were immunopositive for M18-1. The MIB-1 -positive index of our case was extremely high, compared with that of ordinary papillary carcinoma. This case indicates that biological growth activity in columnar cell carcinoma may be similar to that of undifferentiated carcinoma of the thyroid, since the MIB-1 -positive index is close to each other.

Columnar cell carcinoma of the thyroid

A case of columnar cell carcinoma of the thyroid occurring in a 50-year-old female is described. Histologically, the 2 cm tumor showed a prominent papillary architecture with thin fibrous cores covered by columnar cells and marked nuclear stratification. It also showed microfollicular, glandular, and solid patterns. The nuclear features were different to those of conventional papillary carcinoma and similar to those of follicular tumors. The tumor was principally encapsulated with vascular and minimal capsular invasion. The tumor cells were positive for thyroglobulin. The tumor was DNA diploid with a low S phase traction as determined by flow cytometry. The patient had no lymph node or distant metastasis. The patient was well and without disease 9 months after surgery. The possibility that the neoplasm is one of poorly differentiated thyroid carcinomas rises.

TGFB, TGFB Receptors, Ki-67, and p27(Kip)l Expression in Papillary Thyroid Carcinomas

Although most papillary thyroid carcinomas behave as low-grade neoplasms and are generally associated with a good prognosis, some subgroups of these neoplasms represent more aggressive variants. In order to determine if differences in the behavior of these papillary carcinomas were related to expression of growth factors or cell-cycle proteins, we analyzed a series of papillary carcinomas including the conventional or usual type (n = 27), tall cell (n = 27), diffuse sclerosing (n = 5), and columnar cell (n = 2) variants for expression of transforming growth factor beta (TGB), TGB receptors (TGB-RI and II, the proliferation marker Ki-67, and for the cell-cycle inhibitory protein p27(Kip)1 (p27). All groups of thyroid tumors expressed TGFB and TGFB-RI and RlI by immunohistochemical staining. There was a marked increase in the Ki-67 labeling index after staining with antibody MIB-1 in the columnar cell tumors compared to the other groups, but this difference was not significant because of the small number of tumors in this group. The cell-cycle inhibitory protein p27 was expressed in all groups and was not significantly different between groups. Normal thyroid cells had a higher labeling index for p27 compared to papillary carcinomas. These results indicate that TGFB and TGFB receptors I and II are commonly expressed in the usual and in variant forms of papillary thyroid carcinomas, and that there is decreased expression of p27 protein in all of these neoplasms compared to normal thyroid. The biological basis for the more aggressive behavior of these variants of papillary thyroid carcinoma remains uncertain.