Diagnosis and surgical indications of oxyphilic follicular tumors in Japan: Surgical specimens and cytology

Thyroid Hürthle Cell Carcinoma: Clinical, Pathological, and Molecular Features

Simple Summary

Hürthle cell carcinoma (HCC) represents 3–4% of thyroid carcinoma cases. It is characterized by its large, granular and eosinophilic cytoplasm, due to an excessive number of mitochondria. Hürthle cells can be identified only after fine needle aspiration cytology biopsy or by histological diagnosis after the surgical operation. Published studies on HCC indicate its putative high aggressiveness. In this article, current knowledge of HCC focusing on clinical features, cytopathological features, genetic changes, as well as pitfalls in diagnosis are reviewed in order to improve clinical management.

Abstract

Hürthle cell carcinoma (HCC) represents 3–4% of thyroid carcinoma cases. It is considered to be more aggressive than non-oncocytic thyroid carcinomas. However, due to its rarity, the pathological characteristics and biological behavior of HCC remain to be elucidated. The Hürthle cell is characterized cytologically as a large cell with abundant eosinophilic, granular cytoplasm, and a large hyperchromatic nucleus with a prominent nucleolus. Cytoplasmic granularity is due to the presence of numerous mitochondria. These mitochondria display packed stacking cristae and are arranged in the center. HCC is more often observed in females in their 50–60s. Preoperative diagnosis is challenging, but indicators of malignancy are male, older age, tumor size > 4 cm, a solid nodule with an irregular border, or the presence of psammoma calcifications according to ultrasound. Thyroid lobectomy alone is sufficient treatment for small, unifocal, intrathyroidal carcinomas, or clinically detectable cervical nodal metastases, but total thyroidectomy is recommended for tumors larger than 4 cm. The effectiveness of radioactive iodine is still debated. Molecular changes involve cellular signaling pathways and mitochondria-related DNA. Current knowledge of Hürthle cell carcinoma, including clinical, pathological, and molecular features, with the aim of improving clinical management, is reviewed.

Usability of EU-TIRADS in the Diagnostics of Hürthle Cell Thyroid Nodules with Equivocal Cytology

The aim of this study was to compare the diagnostic effectiveness of EU-TIRADS in two groups of nodules with equivocal cytology (categories III-V of Bethesda system), with and without Hürthle cells (HC and non-HC). The study included 162 HC and 378 non-HC nodules with determined histopathological diagnosis (17.9% and 15.6% cancers). In both groups calculated and expected risk of malignancy (RoM) for high, intermediate and benign risk categories of EU-TIRADS were concordant. RoM for low risk category was higher than expected in both groups, but especially in HC (HC: 13.9%, non-HC: 7.0%, expected: 2-4%). The majority of cancers in HC of that category were follicular thyroid carcinomas (FTC) and Hürthle cell thyroid carcinoma (HTC) (60.0% vs. non-HC: 16.7%). The diagnostic efficacy of EU-TIRADS was lower in HC (the area under the receiver operating characteristics curve (AUC): 0.621, sensitivity (SEN): 44.8%, specificity (SPC): 78.9% for high risk threshold) than in non-HC (AUC: 0.711, SEN: 61.0%, SPC: 77.7%). AUC was the highest for category V (AUC > 0.8, both groups) and the lowest for category IV (inefficient, both group). If intermediate risk category was interpreted as an indication for surgery, 25% of cancers from category III and 21.4% from category IV would not be treated in the HC group (0.0% and 7.4% from non-HC group, respectively). EU-TIRADS does not aid making clinical decisions in patients with cytologically equivocal HC nodules, particularly those classified into category IV of Bethesda System for Reporting Thyroid Cytopathology (BSRTC).

Thyroid nodules with Hürthle cells: the malignancy risk in relation to the FNA outcome category

PURPOSE

The aim was to find whether the presence of Hürthle cells (HC) in a smear influences the categorization of FNA results or the risk of malignancy (RoM) of particular categories of cytological diagnosis.

METHODS

25,220 FNA performed in a single center in years 2005-2017 were analyzed. Almost all the examined patients were exposed to moderate iodine deficiency for most of their lives. The distribution of FNA outcome categories was compared between two groups: with or without HC (HC and non-HC). The RoM was evaluated on the basis of postoperative histopathological examination (3082 patients).

RESULTS

HC were found in 7.5% of diagnostic FNA. HC nodules were classified into categories II (78.2% vs. 91.9%, p < 0.0000) and VI (0.4% vs. 1.2%, p = 0.0017) less often than non-HC nodules, but more frequently to categories III (14.4% vs. 5.8%, p < 0.0000), IV (11.2% vs. 0.9%, p < 0.0000) and V (1.5% vs. 0.8%, p = 0.0013). There were no significant differences in RoM between HC and non-HC nodules. The RoM in HC and non-HC nodules of particular categories of the Bethesda system was as follows: II: 1.8% vs. 0.8%, III: 9.7% vs. 3.8% when only the last FNA was considered and 10.8% vs. 6.4% when the category III in any performed FNA was considered; IV: 12.7% vs. 10.9%; V: 41.7% vs. 58.2%; and VI: 100% vs. 96.9%.

CONCLUSIONS

HC nodules are classified into categories of equivocal cytological outcomes more often than nodules without HC. Nevertheless, the presence of HC in a smear does not significantly affect the RoM of FNA categories.

Diagnostic performance of thyroid ultrasound in Hürthle cell carcinomas

OBJECTIVE

Hürthle cell carcinomas (HCCs) of the thyroid have been recently reclassified as a separate entity due to their distinct clinical and molecular profiles. Few studies have assessed the ability of preoperative characteristics in differentiating HCCs from Hürthle cell adenomas (HCAs) due to the low prevalence of both lesions. This study aimed to compare the preoperative features of HCCs and HCAs and evaluate the diagnostic performance of ultrasound in distinguishing between both.

SUBJETCS AND METHODS

Retrospective study including 101 patients (52 HCCs and 49 HCAs) who underwent thyroid surgery from 2000 to 2016. Clinical, ultrasonographic, and histological data were reviewed. Diagnostic performance of suspicious sonographic features was analyzed in 51 cases (24 HCCs and 27 HCAs).

RESULTS

Hürthle cell neoplasms were predominant in females. Subjects ≥ 55 years represented 58% of the cases of HCCs and 53% of those of HCAs. Carcinomas were significantly larger (p < 0.001), and a tumor size ≥ 4 cm significantly increased the risk of malignancy (odds ratio 3.67). Other clinical, cytologic, and sonographic data were similar between HCCs and HCAs. Among the HCCs, the lesions were purely solid in 54.2%, hypoechoic in 37.5%, and had coarse calcifications in 12.5%, microcalcifications in 8.3%, irregular contours in 4.2%, and a taller-than-wide shape in 16.7%. Predominantly/exclusive intranodular vascularization was observed in 52.6%. Overall, 58% of the HCCs were classified as TI-RADS 4 or 5 compared with 48% of the HCAs. TI-RADS 4 or 5 had a specificity of only 51.8% and a positive likelihood ratio of 1.21.

CONCLUSIONS

Apart from the lesion size, no other preoperative feature adequately distinguished HCCs from HCAs. Sonographic characteristics raising suspicion for malignancy, which are mostly present in papillary carcinomas, were infrequent in HCCs. New tools must be developed to improve preoperative diagnosis and deferral of surgery in cases of adenomas.

Impact of the modification of the diagnostic criteria in the 2017 Bethesda System for Reporting Thyroid Cytopathology: a report of a single institution in Japan

The Bethesda System for Reporting Thyroid Cytopathology has recently been revised in 2017 (TBSRTC 2017). This study aimed to evaluate the impact of modifying the diagnostic criteria in TBSRTC 2017 at a single institute. We retrospectively reviewed cytological specimens of 10,399 thyroid nodules submitted for thyroid fine-needle aspiration cytology. Among them, 56 atypia of undetermined significance or follicular lesion of undetermined significance (AUS/FLUS) nodules, 16 suspicious for malignancy (SFM) nodules, and 8 malignant nodules were re-categorized into follicular neoplasm or suspicious for a follicular neoplasm (FN/SFN). The incidence of FN/SFN was increased by 0.8%, while that of AUS/FLUS, SFM, and malignant nodule was decreased by 0.5%, 0.2%, and 0.1%, respectively. In nine (60%) of the 15 nodules that were re-classified from AUS/FLUS to FN/SFN nodules and re-aspiration was performed, it was possible to judge whether they were benign or malignant. Of the 24 patients with FN/SFN nodules originally diagnosed with SFM or malignant, 16 were followed up without surgical resection. In conclusion, TBSRTC 2017 only caused minor changes in the incidence of each diagnostic category. TBSRTC 2017 was revised to avoid false positives owing to noninvasive follicular thyroid neoplasm with papillary-like nuclear features (NIFTP) that account for >10% of papillary thyroid carcinomas; however, it is not necessary in low frequency NIFTP institutes or countries. In Japan, we propose active surveillance as an accepted option for clinically managing AUS/FLUS, FN/SFN, SFM, or malignant nodules having favorable benign clinical findings or being part of the low-risk group.

Do patients with oxyphilic cell papillary thyroid carcinoma have a poor prognosis? Analysis of the surveillance, epidemiology, and end results database 2004-2013 with propensity score matching

The prognosis of oxyphilic cell papillary thyroid carcinoma (OCPTC) remains unclear. The aim of this study was to investigate the prognosis of OCPTC and provide a new perspective on treatment guidelines for these patients. We investigated a large cohort of DTC patients from the Surveillance, Epidemiology, and End Results (SEER) database between 2004 and 2013. Patient mortality was examined by Kaplan-Meier analyses with log-rank tests and Cox proportional hazards regression analyses. In the study cohort, the rate of cancer-specific mortality per 1000 person-years for OCPTC was lower than that for classic papillary thyroid cancer (CPTC) and follicular thyroid cancer (FTC). According to the multivariate Cox regression model, the cancer-specific and all-cause mortality rates of OCPTC were similar to that of CPTC and FTC. The cancer-specific survival rate in patients with OCPTC was higher than that in patients with FTC, but similar to patients with CPTC, after matching for influential factors using propensity score matching analysis. The unanticipated prognosis provided new implications for the treatment of patients with OCPTC.