A potential diagnostic pitfall for hobnail variant of papillary thyroid carcinoma

Oncocytic Follicular Cell-Derived Thyroid Tumors With Papillary Growth Pattern: A Clinicopathologic Study of 32 Cases

CONTEXT.—

Oncocytic thyroid tumors displaying a papillary growth pattern are rare and may cause diagnostic problems.

OBJECTIVE.—

To examine the clinicopathologic features of a series of 32 follicular cell-derived tumors composed of cells with oncocytic cytoplasm and displaying papillary architecture.

DESIGN.—

Thirty-two cases were collected and studied to assess clinicopathologic features, including immunohistochemical and molecular testing for BRAF V600E.

RESULTS.—

The patients were 26 women and 6 men, aged 17 to 77 years. The nodules ranged from 0.3 to 6.0 cm. Eighteen cases showed features of oncocytic hyperplastic nodules and were identified against a background of thyroid follicular nodular disease; 4 cases showed features of oncocytic follicular adenoma; and 10 cases corresponded to carcinomas with oncocytic and papillary features. Nuclear features of papillary thyroid carcinoma were absent or exceedingly rare. All cases were negative for HBME-1 and cytokeratin 19 (CK19) and wild type for BRAF V600E. Follow-up in 25 patients showed that all patients with hyperplastic nodules and oncocytic follicular adenomas were alive and well and free of disease from 7 to 20 years. One patient with oncocytic follicular carcinoma showed metastases and died of tumor at 16 months; 2 patients with carcinoma had metastases and recurrence at 6 and 7 years; and 5 patients with invasive tumors were free of disease from 5 to 10 years.

CONCLUSIONS.—

Oncocytic thyroid tumors with papillary features can span a spectrum from benign hyperplastic, to encapsulated neoplastic, to invasive malignant lesions. Owing to their papillary features, it is important not to confuse them for other types of thyroid tumors, such as oncocytic papillary thyroid carcinoma.

PD-L1 and B7-H3 are Effective Prognostic Factors and Potential Therapeutic Targets for High-Risk Thyroid Cancer

The prognosis of thyroid cancer in patients varies significantly based on different pathological types or distinct clinical situations. Investigating the expression of immune checkpoint molecules PD-L1 and B7-H3 in high-risk thyroid cancer and their correlation with clinicopathological features and prognosis will contribute to the development of novel therapeutic strategies. A retrospective sample of 202 patients with thyroid cancer who underwent surgery at the Cancer Hospital of the Chinese Academy of Medical Sciences was collected, including 33 cases of anaplastic thyroid cancer (ATC), 21 cases of differentiated thyroid cancer (DTC) with distant metastasis (DM), 7 cases of differentiated high-grade thyroid carcinoma (DHGTC), and 109 cases of aggressive subtypes of papillary thyroid carcinoma (PTC) (including 28 cases of tall cell PTC, 31 cases of diffuse sclerosing PTC, 20 cases of solid PTC, 15 cases of columnar cell PTC, and 15 cases of hobnail PTC). In the control group, there were 32 cases of classic PTC. The differences in protein expression between PD-L1 and B7-H3 in several high-risk thyroid cancers and normal tissues and controls were compared by immunohistochemical staining, and the clinicopathological features and prognostic relevance were statistically analyzed. The expression of PD-L1 in ATC (P < 0.001), tall cell PTC (P = 0.031), and DHGTC (P = 0.003) was significantly higher than that in classic PTC. The expression of B7-H3 in ATC (P < 0.001), DTC with DM (P = 0.001), diffuse sclerosing PTC (P = 0.013), columnar cell PTC (P = 0.007), solid PTC (P < 0.001), hobnail PTC (P < 0.001), and DHGTC (P < 0.001) was significantly higher than that in classic PTC. In ATC, PD-L1 expression correlated significantly with extrathyroidal extension (ETE) (P = 0.027) and B7-H3 expression correlated significantly with male patients (P = 0.031) and lymph node metastasis (LNM) (P = 0.026). The positive expression of B7-H3 (P = 0.041) was an independent risk factor for disease progression in ATC. B7-H3 positive expression (P = 0.049), PD-L1 positive expression (P = 0.015), and tumor diameter ≥ 2 cm (P = 0.038) were independent risk factors for disease progression in patients with DTC with DM. PD-L1 positive expression (P = 0.019) and tumor diameter ≥ 2 cm (P = 0.018) were independent risk factors for disease progression in patients with aggressive subtypes of PTC. B7-H3 and PD-L1 are expected to be effective prognostic indicators for patients with aggressive thyroid cancer, which can help in optimization of individualized treatment strategies. Immunotherapy targeting these two molecules may provide new and complementary ideas for the treatment of high-risk/refractory thyroid cancer.

Pathology and new insights in thyroid neoplasms in the 2022 WHO classification

PURPOSE OF REVIEW

The assessment of thyroid nodules is a common clinical problem, linked to the high incidence of thyroid nodules in the population and the low incidence of aggressive thyroid carcinoma. The screening is therefore one of the strengths of our patient care. Recently, the 2023 Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) and 2022 WHO classification of thyroid neoplasms have been released based on the definition of new entities and the growing impact of molecular testing. The aim of this review is to analyze how these upgrades can help us in the daily routine practice diagnosis of thyroid cancer.

RECENT FINDINGS

Our review is focused on the most frequent thyroid tumors derived from thyroid follicular cell. Fine needle aspiration (FNA) is the gold standard for the screening of thyroid nodules with very high levels of sensitivity and specificity. These sensitivity and specificity are improved by molecular testing, which refines the risk of malignancy. The 2023 TBSRTC integrates molecular data and the upgrades integrated in the 2022 WHO classification such as the 'low-risk neoplasms' and the 'high-grade follicular-cells derived carcinoma'. The morphological examination remains crucial since the capsular and/or vascular invasion are key features of malignancy in the follicular thyroid neoplasms. Low-risk neoplasms represent a clinical challenge since no specific guidelines are available. Challenges remain regarding oncocytic thyroid lesions, which are not associated with specific diagnostic molecular biomarkers. Molecular testing can help not only in deciphering the prognosis but also in the targeted therapeutic strategy.

SUMMARY

While molecular testing has succeeded to substantially improve the pre and postoperative diagnosis and risk stratification of thyroid tumors, the morphological examination is still central in the daily routine diagnosis of thyroid pathology. Future is the integrated diagnosis of clinical, morphological, molecular and epigenetic features with the help of artificial intelligence algorithms.

Update from the 2022 World Health Organization Classification of Thyroid Tumors: A Standardized Diagnostic Approach

The fifth edition of the World Health Organization (WHO) histologic classification of thyroid neoplasms released in 2022 includes newly recognized tumor types, subtypes, and a grading system. Follicular cell-derived neoplasms are categorized into three families (classes): benign tumors, low-risk neoplasms, and malignant neoplasms. The terms "follicular nodular disease" and "differentiated high-grade thyroid carcinoma" are introduced to account for multifocal hyperplastic/neoplastic lesions and differentiated thyroid carcinomas with high-grade features, respectively. The term "Hürthle cells" is replaced with "oncocytic cells." Invasive encapsulated follicular and cribriform morular variants of papillary thyroid carcinoma (PTC) are now redefined as distinct tumor types, given their different genetic alterations and clinicopathologic characteristics from other PTC subtypes. The term "variant" to describe a subclass of tumor has been replaced with the term "subtype." Instead, the term "variant" is reserved to describe genetic alterations. A histologic grading system based on the mitotic count, necrosis, and/or the Ki67 index is used to identify high-grade follicular-cell derived carcinomas and medullary thyroid carcinomas. The 2022 WHO classification introduces the following new categories: "salivary gland-type carcinomas of the thyroid" and "thyroid tumors of uncertain histogenesis." This review summarizes the major changes in the 2022 WHO classification and their clinical relevance.

Hobnail Papillary Thyroid Carcinoma, A Systematic Review and Meta-Analysis

Although papillary thyroid carcinoma (PTC) is considered to have an excellent prognosis, some recently identified more aggressive variants show reduced overall survival rates. Hobnail PTC (HPTC) was newly recognized as one of these aggressive forms, affecting recurrence, metastasis, and overall survival rates. Herein, we performed a systematic review and meta-analysis of studies including cases or case series with patients with HPTC. Furthermore, we included our individual case series consisting of six patients. The pooled mortality rate in the cohort, consisting of 290 patients, was 3.57 (95% CI 1.67−7.65) per 100 person/years. No sex differences could be observed concerning mortality (p = 0.62), but older age and tumor size significantly affected mortality (p = 0.004 and p = 0.02, respectively). The percentage of hobnail cells did not affect mortality (p = 0.97), neither did the presence of BRAF mutations. Classical characteristics such as the presence of extrathyroidal extension (p = 0.001), distant metastases (p < 0.001), and lymph node metastases (p < 0.001) all had a significant impact on mortality. Thus, HPTC appears to correlate with worse overall survival, and all PTC cases should be carefully assessed for this variant.

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

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

Papillary thyroid carcinoma with hobnail features showing rapid progression and therapy resistance

BACKGROUND

Hobnail variant of papillary thyroid carcinoma (HVPTC), also designated as a micropapillary variant, is a rare but aggressive variant of PTC, representing <2% of all PTC. It was adopted in the newest World Health Organization classification. HVPTC is strongly associated with higher mortality in comparison to classic PTC and a high propensity for disease progression. This paper aimed to investigate the clinical course, cytological and histopathological features, and mutational profile of the hobnail variant from a unique case.

CASE REPORT

A case of a 38-year-old female patient with HVPTC is presented. Total thyroidectomy with central and bilateral, lateral lymphadenectomy was performed. The clinical course showed aggressive features, as lymph node metastasis and extrathyroidal extension were present at the presentation. Molecular and immunohistochemical features are addressed along with a review of the literature.

DISCUSSION

The cytological examination of FNA was in consonance with published literature. The cells showed hobnail features in several segments of both thyroidal lobes on histological examination. The tumour displayed a typical BRAF mutation and Gly12Ala mutation in the KRAS gene, previously not associated with PTC.

CONCLUSION

We aimed to highlight the aggressive, clinicopathological features of this high-risk variant. We emphasise the need to evaluate suspicious thyroid nodules as an adequate diagnosis can prevent delayed therapy. It directly impacts the tumour's stage and prognosis. In fine-needle aspiration cytology showing papillary architecture carcinomas, HVPTC has to be part of the differential diagnosis.

Hobnail variant of papillary thyroid carcinoma: a systematic review and meta-analysis

OBJECTIVE

The hobnail variant of papillary thyroid carcinoma (HVPTC) has emerged as a rare and aggressive variant of papillary thyroid carcinoma (PTC). We aim to determine the prevalence and clinicopathologic factors of HVPTC.

METHODS

A systematic review of the literature for studies examining HVPTC was performed. Four databases (PubMed, Scopus, OVID, Cochrane library) were queried from inception of databases through March 20th, 2020.

RESULTS

Sixteen studies with 124 cases of HVPTC were included. The mean age for all patients was 52.3 years. HVPTC had a prevalence of 1.08% out of all PTC cases, with a mean tumor size of 3.1 cm. In 62% and 50% of cases, lymphovascular invasion and extrathyroidal extension were present, respectively. Follow-up data, with a mean of 49.9 months, revealed a 66% rate of lymph node metastasis and 23% rate of distant metastasis. Tumors with ≥30% hobnail morphology had a 2.6-fold increased odds of developing lymph node metastasis compared with <30% hobnail morphology, however did not differ in rates of distant metastasis. Patients ≥55 years old had a 4.5-fold increased odds of distant metastasis and a 4.7-fold increased odds of lymphovascular invasion over patients <55.

CONCLUSIONS

High rates of locoregional and distant disease as well as high-risk pathological factors reveal the aggressive nature of HVPTC. Diagnostic criteria regarding percentage of hobnail morphology requires further refinement. Further studies are warranted in order to better understand how recognition of this high-risk variant impacts clinical treatment.

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.

Molecular Pathology of Non-familial Follicular Epithelial-Derived Thyroid Cancer in Adults: From RAS/BRAF-like Tumor Designations to Molecular Risk Stratification

This review addresses the impact of molecular alterations on the diagnosis and prognosis of differentiated thyroid carcinoma (DTC), including papillary, follicular, and well-differentiated carcinoma NOS, as well as oncocytic neoplasms. The molecular characterization of DTC is based upon the well-established dichotomy of BRAF-like and RAS-like designations, together with a remaining third group, less homogeneous, composed of non-BRAF-/non-RAS-like tumors. The role of BRAF V600E mutation in risk stratification is discussed in the clinico-pathological context, namely, staging and invasive features of classic papillary thyroid carcinoma (PTC) and histopathological variants carrying an excellent prognosis (microPTC) or a guarded prognosis, including the aggressive variants tall cell and hobnail cell PTCs. In follicular patterned tumors, namely, follicular thyroid carcinoma (FTC), with or without oncocytic features, the most prevalent molecular alteration are RAS mutations that do not carry prognostic significance. The only genetic alteration that has been proven to play a role in risk stratification of PTC and FTC is TERT promoter (TERTp) mutation.

Updates in the Pathologic Classification of Thyroid Neoplasms: A Review of the World Health Organization Classification

Advances in medical sciences and evidence-based medicine have led to momentous changes in classification and management of thyroid neoplasms. Much progress has been made toward avoiding overdiagnosis and overtreatment of thyroid cancers. The new 2017 World Health Organization (WHO) classification of thyroid neoplasms updated the diagnostic criteria and molecular and genetic characteristics reflecting the biology and behavior of the tumors, and newly introduced the category of borderline malignancy or uncertain malignant potential. Some neoplasms were subclassified, renamed, or redefined as a specific entity. This review introduces changes in the fourth edition WHO classification of thyroid tumors and updates the contemporary diagnosis and classification of thyroid tumors. We also discuss several challenges with the proposal of new diagnostic entities, since they have unique histopathologic and molecular features and clinical relevance.

Pitfalls in Challenging Thyroid Tumors: Emphasis on Differential Diagnosis and Ancillary Biomarkers

Thyroid pathology encompasses a heterogenous group of clinicopathological entities including rare and diagnostically challenging neoplasms. The review is focused on morphological, immunohistochemical, and molecular features of rare thyroid neoplasms that can pose diagnostic problems. The tumors are organized based on growth patterns including thyroid neoplasms with predominantly papillary, follicular, solid, and spindle cell growth pattern, as well as neoplasms with distinct cytological characteristics. A special section is also dedicated to rare thyroid tumors with peculiar patterns including thyroid carcinoma with Ewing family tumor elements and intrathyroidal thymic-related neoplasms.

Papillary Thyroid Cancer-Aggressive Variants and Impact on Management: A Narrative Review

Introduction

Aggressive variants of papillary thyroid cancer (PTC) have been described with increasing frequency. These variants include diffuse sclerosing variant, tall cell variant, columnar cell variant, solid variant, and hobnail variant.

Methods

We have performed a review of the more aggressive variants of PTC with respect to main characteristics, histological and molecular features, and the consequences that the knowledge of these variants should have in the treatment of the patients.

Results

At the present time, we do not know the prognostic value of these aggressive PTC variants. The extent of the surgical treatment and adjuvant therapy necessary should be decided on the basis of the extent of the tumor at presentation and the opinion of experienced clinicians.

Conclusion

These aggressive variants should be known by clinicians, to avoid underdiagnosis, and treated according to the latest recommendations in the literature.