Thyroid follicular neoplasm: analysis by fine needle aspiration cytology, frozen section, and histopathology

Using Deep Convolutional Neural Networks for Enhanced Ultrasonographic Image Diagnosis of Differentiated Thyroid Cancer

Differentiated thyroid cancer (DTC) from follicular epithelial cells is the most common form of thyroid cancer. Beyond the common papillary thyroid carcinoma (PTC), there are a number of rare but difficult-to-diagnose pathological classifications, such as follicular thyroid carcinoma (FTC). We employed deep convolutional neural networks (CNNs) to facilitate the clinical diagnosis of differentiated thyroid cancers. An image dataset with thyroid ultrasound images of 421 DTCs and 391 benign patients was collected. Three CNNs (InceptionV3, ResNet101, and VGG19) were retrained and tested after undergoing transfer learning to classify malignant and benign thyroid tumors. The enrolled cases were classified as PTC, FTC, follicular variant of PTC (FVPTC), Hürthle cell carcinoma (HCC), or benign. The accuracy of the CNNs was as follows: InceptionV3 (76.5%), ResNet101 (77.6%), and VGG19 (76.1%). The sensitivity was as follows: InceptionV3 (83.7%), ResNet101 (72.5%), and VGG19 (66.2%). The specificity was as follows: InceptionV3 (83.7%), ResNet101 (81.4%), and VGG19 (76.9%). The area under the curve was as follows: Incep-tionV3 (0.82), ResNet101 (0.83), and VGG19 (0.83). A comparison between performance of physicians and CNNs was assessed and showed significantly better outcomes in the latter. Our results demonstrate that retrained deep CNNs can enhance diagnostic accuracy in most DTCs, including follicular cancers.

Risk Stratification in Patients With Follicular Neoplasm on Cytology: Use of Quantitative Characteristics and Sonographic Patterns

OBJECTIVES

Differentiating thyroid nodules with a cytological diagnosis of follicular neoplasm remains an issue. The goal of this study was to determine whether ultrasonographic (US) findings obtained preoperatively from the computer-aided detection (CAD) system are sufficient to further stratify the risk of malignancy for this diagnostic cytological category.

METHODS

From September 2016 to September 2018 in our hospital, patients diagnosed with Bethesda category IV (follicular neoplasm or suspicion of follicular neoplasm) thyroid nodules and underwent surgical excisions were include in the study. Quantification and analysis of tumor features were performed using CAD software. The US findings of the region of interest, including index of composition, margin, echogenicity, texture, echogenic dots indicative of calcifications, tall and wide orientation, and margin were calculated into computerized values. The nodules were further classified into American Thyroid Association (ATA) and American College of Radiology Thyroid Imaging Reporting & Data System (TI-RADS) categories.

RESULTS

92 (10.1%) of 913 patients were diagnosed with Bethesda category IV thyroid nodules. In 65 patients, the histological type of the nodule was identified. The quantitative features between patients with benign and malignant conditions differed significantly. The presence of heterogeneous echotexture, blurred margins, or irregular margins was shown to have the highest diagnostic value. The risks of malignancy for nodules classified as having very low to intermediate suspicion ATA, non-ATA, and high suspicion ATA patterns were 9%, 35.7%, and 51.7%, respectively. Meanwhile, the risks of malignancy were 12.5%, 26.1%, and 53.8% for nodules classified as TIRADS 3, 4, and 5, respectively. When compared to human observers, among whom poor agreement was noticeable, the CAD software has shown a higher average accuracy.

CONCLUSIONS

For patients with nodules diagnosed as Bethesda category IV, the software-based characterizations of US features, along with the associated ATA patterns and TIRADS system, were shown helpful in the risk stratification of malignancy.

Frozen section in thyroid gland follicular neoplasms: It's high time to abandon it!

Thyroid nodules are a very common clinical condition. The 2015 American Thyroid Association (ATA) guidelines recommend surgical excision for Bethesda IV nodules. The use of intraoperative frozen section (FS) has been recommended as a strategy to tailor the extent of the initial surgery. We critically evaluated the literature that discusses the utility and cost-effectiveness of FS to make an intraoperative decision in patients with thyroid nodules classified as follicular neoplasm. FS should not be recommended as a routine intraoperative test to assess for malignancy in thyroid follicular patterned lesions due to its low performance; the high number of deferred results; the inability to adequately assess histologically defining features; the improvements in risk stratification guiding total thyroidectomy; and the low cost-effectiveness of FS.

Thyroid fine-needle aspiration cytology in Taiwan: a nationwide survey and literature update

In Taiwan, thyroid fine-needle aspiration cytology is easily accessible and reliable for evaluating thyroid nodules. The sonographic pattern plays a major role and is the deciding factor for aspiration. We conducted a nationwide survey in 2017 and it revealed that 31% of laboratories had adopted The Bethesda System for Reporting Thyroid Cytopathology. There was a relatively high unsatisfactory rate (24.04%) and low rates of indeterminate diagnoses, including atypia of undetermined significance/follicular lesions of undetermined significance: 4.87%, and follicular neoplasm/suspicious for a follicular neoplasm: 0.35%. Moreover, the risks of malignancy in benign, atypia of undetermined significance, and suspicious for a follicular neoplasm were relatively high. These may reflect strict diagnostic criteria for indeterminate categories and better patient selection for surgery. Improvements in specimen sampling and continuing education programs are crucial. Newly-developed thyroid cytology technologies, such as immunocytochemistry, molecular testing, and computerized cytomorphometry, may further facilitate cytology diagnoses.

Utility of Routine Frozen Section of Thyroid Nodules Classified as Follicular Neoplasm

OBJECTIVES

To evaluate the diagnostic performance of frozen section in thyroid nodules classified as follicular neoplasm.

METHODS

A diagnostic test meta-analysis was designed. Studies that assessed frozen section in patients with thyroid nodules and a fine-needle aspiration biopsy result of Bethesda IV were selected. The outcomes measured were the number of false- and true-positive and -negative results. We used the Quality Assessment of Diagnostic Accuracy Studies 2 (QUADAS-2) instrument for methodological quality assessment and a bivariate mixed-effects regression framework and a likelihood-based estimation of the exact binomial approach.

RESULTS

Forty-six studies from 1991 to 2018 were included. Most studies had moderate methodological quality. The overall sensitivity and specificity were 43% (95% confidence internal [CI], 0.34-0.53) and 100% (95% CI, 0.99-1.00), respectively. The hierarchic summary receiver operating characteristic curve showed an area under the curve of 0.91 (95% CI, 0.80-0.97).

CONCLUSIONS

Frozen section demonstrates moderate diagnostic performance in patients with follicular neoplasm, and its utility for making intraoperative decisions is limited. Its routine use should be discouraged.

A Retrospective Study to Assess the Role of Using Fine Needle Aspiration Cytology and Frozen Section in the Diagnosis of Thyroid Swelling

The most cost-effective test is fine needle aspiration cytology (FNAC). Many surgeons use intraoperative frozen section to confirm the FNAC findings and to guide the extent of thyroid surgery. Though it is a valuable tool in the diagnosis of the thyroid lesion and determining the extent of thyroid surgery, still in certain cases diagnosis can be incorrect or inconclusive, so histopathology of the excised specimen remains the most reliable test. The purpose of this study will be to compare the result attained by FNAC and frozen section of the thyroid to the final histopathological diagnosis, in order to establish their role in thyroid surgery today. A retrospective study with a total of 140 patients who underwent thyroid surgery at the ENT department, of a tertiary hospital in coastal Karnataka. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were calculated for FNAC and frozen section. The sensitivity, specificity, positive predictive rate, and negative predictive rate of frozen section was found to be 66.7%, 88.4%,76.6%, 82.4% respectively for detecting malignancy. This was found to be higher than the results of FNAC for the same which were 64.4%, 77.8%, 64.4%, 77.8% respectively. As the sensitivity of FNAC is similar to frozen section in detecting malignant cases, FNAC is a good tool for screening the patient for determining malignancy in thyroid, but frozen section is more specific in confirming the malignancy.

Thyroid Fine-Needle Aspiration in Taiwan: The History and Current Practice

In Taiwan, thyroid cancer is the most common endocrine gland malignancy and the incidence of thyroid cancer has increased four-fold in the past two decades. Fine-needle aspiration is an accurate and cost-effective method of evaluating thyroid nodules and has been the gold-standard diagnostic tool for thyroid tumors in Taiwan since the 1980s. This article reviews the history, current practice, reporting systems, training, and quality assurance for thyroid fine-needle aspiration cytology in Taiwan.

The futility of intraoperative frozen section in the evaluation of follicular thyroid lesions

OBJECTIVE

Investigate the utility of intraoperative frozen section (iFS) in patients with follicular thyroid lesions following publication of the 2015 American Thyroid Association (ATA) guidelines.

STUDY DESIGN

Retrospective chart review.

METHODS

Patient demographics, preoperative cytology, frozen pathology, and final pathology were reviewed on patients undergoing thyroid surgery at a tertiary care hospital in which iFS was utilized over a 5-year period. The test performance of iFS and the frequency of indicated completion/total thyroidectomies pre- and postpublication of the 2015 ATA guidelines were calculated.

RESULTS

One hundred and one patients met inclusion criteria: 54 patients with follicular lesions of undetermined significance (FLUS) and 47 patients with a cytologic diagnosis of suspicious for follicular neoplasm/follicular neoplasm. The malignancy rate was 36%, but only 14% of malignancies were identified on iFS. A definitive benign or malignant diagnosis was given on iFS in only 21% of cases, and operative management was altered in two cases as a result of iFS. There was a statistically significant reduction in the frequency of indicated total/completion thyroidectomies based on high-risk features as a result of the 2015 ATA guidelines compared to prior recommendations (20.8% vs. 5.0%, P = < 0.001). None of these patients had findings on iFS that would have altered management intraoperatively.

CONCLUSION

Intraoperative frozen section offers minimal diagnostic utility in the evaluation of follicular thyroid lesions. Updates in the 2015 ATA guidelines further diminish its potential to impact management intraoperatively. Significant improvements in its ability to identify malignancies would be needed to justify its use.

LEVEL OF EVIDENCE

4. Laryngoscope, 128:1501-1505, 2018.

Extremely Well-Differentiated Papillary Thyroid Carcinoma Resembling Adenomatous Hyperplasia Can Metastasize to the Skull: A Case Report

We describe herein histologic, immunohistochemical, and molecular findings and clinical manifestations of a rare case of an extremely well differentiated papillary thyroid carcinoma (EWD-PTC). Similarly, it is also difficult to diagnose follicular variant papillary thyroid carcinoma (FVPTC), whose diagnosis is still met with controversy. A recently reported entity of well-differentiated tumor of uncertain malignant potential (WDT-UMP) is added to the diagnostic spectrum harboring EWD-PTC and FVPTC. We report this case, because EWD-PTC is different from FVPTC in its papillary architecture, and also from WDT-UMP in its recurrence and metastatic pattern. These morphologically deceptive entities harbored diagnostic difficulties in the past because the diagnosis depended solely on histology. However, they are now diagnosed with more certainty by virtue of immunohistochemical and molecular studies. We experienced a case of EWD-PTC, which had been diagnosed as adenomatous hyperplasia 20 years ago and manifested recurrence with lymph node (LN) metastasis 7 years later. After another 7 years of follow-up, a new thyroid lesion had developed, diagnosed as FVPTC, with LN metastasis of EWD-PTC. One year later, the patient developed metastatic FVPTC in the skull. Immunohistochemically, the EWD-PTC was focally positive for CK19, negative for galectin-3, and focally negative for CD56. Molecular studies revealed BRAF-positivity and K-RAS negativity. The FVPTC in the left thyroid showed both BRAF and K-RAS negativity. In conclusion, EWD-PTC and FVPTC share similar histologic features, but they are different tumors with different molecular biologic and clinical manifestations. A large cohort of EWD-PTC should be included in further study.

A risk model to determine surgical treatment in patients with thyroid nodules with indeterminate cytology

BACKGROUND

Thyroid nodules are present in 19-67 % of the population and have a 5-10 % risk of malignancy. Fine needle aspiration biopsies are indeterminate in 20-30 % of patients, often necessitating thyroid surgery for diagnosis. We hypothesized that developing a risk model incorporating factors associated with malignancy could help predict the risk of malignancy in patients with indeterminate thyroid nodules.

METHODS

We identified 151 patients with a cytologic diagnosis of follicular neoplasm (Bethesda IV) who progressed to surgery. We retrospectively analyzed demographic, clinical, sonographic, and cytological variables in relation to thyroid carcinoma.

RESULTS

Of 151 patients, 51 (33.8 %) had a final diagnosis of thyroid carcinoma. Papillary carcinoma was diagnosed in 34 patients (66.7 %), follicular carcinoma in 15 (29.4 %), and Hürthle cell carcinoma in 2 (3.9 %). On univariate analysis, younger age, male gender, tobacco use, larger nodule size, and calcifications on ultrasound, nuclear atypia on cytology, and suspicious frozen section were associated with the presence of malignancy. When determining odds ratios, four factors were most predictive of malignancy: nodule calcification [odds ratio (OR) 6.37, 95 % confidence interval (CI) 1.62-25.1, p < 0.01] and nodule size (OR 1.75, 95 % CI 1.19-2.57, p < 0.01) on ultrasound, nuclear atypia on cytology (OR 4.91, 95 % CI 1.90-12.66, p < 0.01), and tobacco use (OR 4.59, 95 % CI 1.30-16.27, p < 0.02). A multivariable model based on these four factors resulted in a c-statistic of 0.82.

CONCLUSIONS

A multivariable model based on calcification, nodule size, nuclear atypia, and tobacco use may predict the risk of thyroid cancer requiring a total thyroidectomy in patients with thyroid nodules of indeterminate cytology.

Quality Appraisal of Diagnostic Accuracy Studies in Fine-Needle Aspiration Cytology: A Survey of Risk of Bias and Comparability

Context.—The quality of diagnostic accuracy studies is determined by 2 key factors: risk of bias and comparability. Bias can distort accuracy estimates and poor reporting impairs comparability. While diagnostic accuracy studies for fine-needle aspiration cytology (FNAC) are frequently published, the methodologic issues associated with this body of literature have never been reviewed.

Objective.—To assess the quality of design and reporting of diagnostic test accuracy studies in FNAC.

Data Sources.—Diagnostic accuracy studies were identified by a Medline (US National Library of Medicine) search. Sixty-four FNAC diagnostic test accuracy studies were randomly selected for structured review with the Quality Assessment of Diagnostic Accuracy Studies (QUADAS) survey. Studies were divided between 2 time periods: 2000-2001 and 2009-2011.

Conclusions.—Diagnostic test accuracy studies of FNAC suffer from numerous deficiencies in study design, which negatively affect the reliability of accuracy estimates.