Translate this page into:
The diagnostic value of add-on thyroid cell block in the evaluation of thyroid lesions

-
Received: ,
Accepted: ,
How to cite this article: Saharti S. The diagnostic value of add-on thyroid cell block in the evaluation of thyroid lesions. CytoJournal 2023;20:3.
HTML of this article is available FREE at: https://dx.doi.org/10.25259/Cytojournal_9_2022
Abstract
Objectives:
Fine-needle aspiration (FNA) cytology plays a pivotal role in diagnosing thyroid nodules. Imaging assessment, followed by thyroid lesion sampling, is a widely applied clinical practice. Tissue fragments remnants are retrieved in cell-block providing an adjunct diagnostic tool for histopathology visualization and use of ancillary testing. This study aimed to evaluate whether the auxiliary application of cell-block adds to the diagnostic accuracy of the thyroid FNA.
Material and Methods:
A total of 252 thyroid FNA cases between (2020 and 2021) were reviewed from patients aged 18–76. Of those, 150 cell-blocks were recovered and examined to assess their utility. Following categories were plotted during cell-blocks revision: (A) Inadequate material retrieved; (B) cell-block shows similar features along with their accompanying smears; and (C) value added to cytology diagnosis when using cell-block.
Results:
The distribution of cell-blocks according to the aforementioned classification are as follows: A — non-diagnostic 63%, B — similar observation seen in both preparations 35%, and C — value added to the rendered diagnosis 2%. Hence, the use of cell-block improved cytology diagnosis in only 2% of total cases. Mostly were of immunostains application for diagnosis confirmation.
Conclusion:
The non-diagnostic and atypical cytology cases have not been upgraded to a more meaningful category by the incorporation of cell-block performed with the routine non-enhancement random method. On the other hand, cell-blocks contributed generously toward immunostaining application in malignant scenarios.
Keywords
Thyroid nodules
Thyroid fine-needle aspiration
Cell-block
INTRODUCTION
The incidence of thyroid neoplasm has been increasing dramatically. It is expected to be the fourth common cancer worldwide by 2030.[1] At the local level, thyroid nodules appear to be fairly frequent in Saudis, perhaps exceeding the 10% incidence of Western adult population.[2] The sensitivity and specificity of fine-needle aspiration (FNA) as a presurgical predictive tool for the evaluation of thyroid nodules have been well established, precisely with the application of the Bethesda System for Reporting Thyroid Cytopathology (TBSRTC) characterization.[3-5] The reported sensitivity and specificity for malignant cases were of 94% and 98.5%, consecutively.[6] However, false positive and false negative calls resulted from FNA readings can lead to remarkable diagnostic pitfalls.[7] False negative results are often caused by inadequate aspirated material; therefore, it is essential to consider additional technique within FNA procedure to enhance the sample adequacy. In some institutions, cell-block materials are performed routinely per the College of American Pathologists 2016 Practice Survey, which reported 73.7% laboratories (575 out of 735 respondents) processing cell-blocks as a common cytopreparation.[8] Nevertheless, limited literatures support their pivotal role in the diagnostic efficacy while others indicate their disadvantages such as labor intensive, skill dependent, and waste of resources.[9,10] This study focuses on the applicability of cell-block implementation in increasing diagnostic effectiveness of thyroid FNA.
MATERIAL AND METHODS
This study received approval from the Committee of Biomedical Ethics at King AbdulAziz University, Jeddah, KSA (No. 402-21). Two years retrospective review (2020– 2021) of the cytopathology archive yielded a total of 252 thyroid FNA cases. All FNAs were done by radiologists under ultrasound guidance using 22-gauge needles (Terumo Neolus® Hypodermic needles). However, larger needles diameter was also used precisely for cystic nodules to tackle the sloid component. Adequacy assessment was achieved based on TBSRTC criteria.[3] Average of two aspirates was done per case, diff-quick stained slides were prepared as well as alcohol-fixed slides for Papanicolaou staining. The needles were rinsed immediately in specimen vials containing SurePath preservative fluid (BD Diagnostics-TriPath, Burlington). For cell-blocks production, needle rinse fluid was centrifuged at 2000 rpm for 5 min and the supernatant was discarded. 10–15 mL of the cell-block preparation mix (200 ml of 100% absolute EMPRATA® ethanol alcohol + 200 mL of 100% absolute Sigma-Aldrich® formalin + 1600 ml of distilled water) was added and the specimen was gently agitated. Then, the specimen was centrifuged at 3400 rpm for 4 min and the supernatant was discarded. To prepare for processing, the pellet was wrapped loosely in a specimen paper with formalin drop, followed by placement in a sealed labeled tissue cassette.
The TBSRTC criteria were applied throughout the diagnosis process.[3] A presence of six clusters of minimums of ten follicular cells on one slide is required for the adequacy assessment call during the rapid on-site evaluation. Although, conditions such as colloid nodules, lymphocytic thyroiditis, and the presence of atypical cells are excluded from these criteria. Images were taken by Nikon’s light microscope.
RESULTS
A total of 252 thyroid FNA cases were collected over 2 years from the right lobe, left lobe, bi-lobed, or isthmus locations [Table 1]. Filtered patients were outweighed by female gender (80%) with different age groups ranging from 18 to 76-years-old. Of those cases, a total of 920 cytology slides and their matched 150 cell-blocks were classified based on TBSRTC category as follows: 38% were benign (II). Cystic configuration and scant cellularity contributed to the 18.5% non-diagnostic category (I). The distributions of AUS/FLUS (III) and FN/SFN (IV) were 18.5% and 17%, respectively. Category-V constituted 2% of the suspicious papillary carcinoma (PTC) cases. PTC was the most common malignancy in the 6% Category-VI, followed by medullary carcinoma (MTC) [Figure 1]. On reviewing, cell blocks were grouped into three classes based on their potential values to the cytology interpretation: Inadequate cell-block, cytology smear findings look alike cell-block, and the last group which provided valuable information to the final diagnosis [Table 2].
Total number of FNA cases | 252 |
Total number of cytology slides | 920 |
Total number of processed cell blocks | 150 |
Number of cell blocks per interpretation | ||||
---|---|---|---|---|
TBSRTC | (A) Acellular cell block | (B) Similar findings seen in cytology slides and their combined cell block | (C) Cell block added a value to the rendered diagnosis | Total |
I | 27 (96%) | 1 (4%) | 0 | 28 (18.5%) |
II | 29 (51%) | 28 (49%) | 0 | 57 (38%) |
III | 25 (89%) | 3 (11%) | 0 | 28 (18.5%) |
IV | 12 (48%) | 13 (52%) | 0 | 25 (17%) |
V | 2 (67%) | 1 (33%) | 0 | 3 (2%) |
VI | 0 | 6 (67%) | 3 (33%) | 9 (6%) |
Total | 95 (63%) | 52 (35%) | 3 (2%) | 150 |

Our data showed that in 63% of the total thyroid FNA cases, cell-blocks interpretation showed no superior value to cytology slides. Of note, aspirates readings and cell-blocks interpretation were interchangeable in 35% of cases. For example, characteristic features of PTC including intranuclear cytoplasmic pseudoinclusion and nuclear grooving were present in both cytology smears and cell-blocks [Figure 2]. On the other hand, the production of cell-blocks added a value to the diagnosis in 2% of FNA cases. For instance, the morphological impression of MTC [Figure 3a and b] was confirmed by immunoreactivity toward calcitonine and CEA [Figure 3c and d].


As of cases that were categorized as inadequate or AUS, the addition of axillary cell-block procedure had no remarkable value.
DISCUSSION
Thyroid cancer is on significant rise. Diagnostic approaches for the detection of thyroid neoplasms include routine ultrasound scanning, FNA, biochemical investigations, and molecular techniques. The most reliable and cost effective diagnostic tool is direct smears obtained from FNA, though their false diagnosis rate is high.[11,12] Different studies confirmed that the use of FNA needle wash material for cell-block could impact TBSRTC Category I.[9-13] Of note, TBSRTC blue book has no clear recommendation on cell-block processing as a routine practice in thyroid FNA cytopreparations. The addition of cell-block ancillary technique was evaluated in our study to test its potential to enhance maximum use of available FNA material. Over 2 years, 150 cell-blocks generated out of 252 FNA thyroid cases were reviewed in pair with their original smears.
Non-diagnostic results can be attributed to multiple factors including aspirator experience and nature of the nodule (cystic vs. solid or fibrotic vs. calcified).[14,15] Rarely, metaplastic squamous cells can present as cystic thyroid nodules and cause a considerable diagnostic pitfall.[16-21] Some studies documented that using ultrasound-guided FNA approach has reduced the rate of non-diagnostic category.[22-24] In our study, all FNAs were performed under ultrasound guidance. Despite that cell-blocks were initially processed to enhance the sample quality, 96% of the unsatisfactory FNA cases have not gained any benefits from the addition of cell-blocks [Table 2].
In parallel, benign thyroid nodules can be a diagnostic dilemma, such as lymphocytic/Hashimoto thyroiditis cases showing lymphoid component that mimics lymphoma.[25-28] However, the presence of classic cytologic features and flow cytometry testing can support the benign impression.[3,26,27] In our study, the characteristic cytologic features of lymphocytic/ Hashimoto thyroiditis were clearly identified on cytology smears by the presence of bland appearing nuclei and oncocytes aggregates mixed with tangled lymphocytes [Figure 4]. Based on these findings, it was not surprising that cell-block technology did not augment the initial cytology call [Table 2].

On the other hand, AUS zone is the most challenging category which contributes to unnecessary surgical resections.[28-33] Therefore, implementation of ancillary techniques could have a great impact on the subsequent management. However, our data showed that that the use of cell-block has not eliminated the number of thyroidectomies in 89% of AUS cases [Table 2].
One of the main advantage of the tissue fragments present in cell-block is maintaining the architecture closely resemble those seen on surgical specimens.[34] Nevertheless, distinguishing between non-invasive follicular thyroid neoplasm and other categories with follicular patterns such as (Follicular Adenoma, Follicular Carcinoma, and PTC-Follicular variant) is impossible by FNA due to the absence of histological criteria.[35-40] Therefore, it is not surprising that the use of cell-block has not improved the cytology diagnosis in 48% of our cases (TBSRTC category IV). Besides, cell-blocks recapitulate the initial interpretation in 52% of their paired-cytology cases without additional significant information [Figure 5]. Of note, 67% of TBSRTC Category V cases were diagnosed mainly by cytomorpholoic features seen on smears/liquid based-slides such as pseudoinclusions and longitudinal nuclear grooves. Former features were absent in the accompanying cell-block. While in 33% of cases, cell-blocks reiterate cytology smears featuring characteristic observations of papillary thyroid carcinoma [Figure 2]. Importantly, 33% of malignant cases were accurately based on immunohistochemistry stains applied on processed cell-blocks [Table 2]. For example, the presence of intranuclear pseudoinclusions which occur occasionally in medullary thyroid carcinoma can be mistaken for papillary thyroid carcinoma. Therefore, immunoreactivity toward calcitonin and CEA stains on cell-block material [Figure 3] had a remarkable impact on rendering the final interpretation.[41-45]

In general, our data showed that cell-block auxiliary testing improved final diagnosis in only 2% of total cases and failed to reduce number of TBSRTC Category I or III cases. In parallel to our findings, the limitation of cell-blocks was described by Horton et al. and Sanchez et al.[9,10] Application of special enhanced cell blocking methods may improve this because of quantitative improvements. In addition, the exposure of needle rinse to SurePath preservative before histology processing could quantitatively and qualitatively compromise sample adequacy.[46-48] Therefore, cell-block processing methodology can be optimized using modern techniques such as proprietary preformed gel disc with wells (Nano NextGen cell-blocking™ kit), which concentrates a nuclei-rich sediment.[49]
To sum up, our study confirmed that the routine processing of cell-blocks is time consuming, impractical, and causes unnecessary delay in the turnaround time. We recommend generating cell-blocks in malignant TBSRTC Categories IV and V if needed for immunostains purposes. In general, the cellularity of cell-blocks can be enhanced by the collaboration between interventional radiologists and interpreting pathologists to yield a robust specimen collection protocols.
CONCLUSION
The generated material from cell-block auxiliary technique did not eliminate TBSRTC Category I or III. It improved cytology diagnosis in 2% of total FNA cases where immunostains are needed. Therefore, our study showed that processing cell-blocks routinely in thyroid aspirates has not significantly aided in increasing the diagnostic yield of unsatisfactory or atypical thyroid samples if routine non-enhancement random methods are used. Further evaluation of optimized cell-block processing methodology utilizing modern enhancement techniques is recommended.
Acknowledgment
This research work was funded by the Institutional Fund Projects under grant no. (IFPIP:97-140-1443). The authors gratefully acknowledge technical and financial support provided by the Ministry of Education and King Abdulaziz University, DSR, Jeddah, Saudi Arabia.
COMPETING INTEREST STATEMENT BY ALL AUTHORS
The author has no conflict of interest to declare.
AUTHORSHIP STATEMENT BY ALL AUTHORS
The author retrieved the data, reviewed the slides and fully contributed to the manuscript.
ETHICS STATEMENT BY ALL AUTHORS
This study was approved by the Committee of Biomedical Ethics at King AbdulAziz University, Jeddah, KSA (No. 402-21). All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. Informed consent was obtained from all individual participants involved in the study.
LIST OF ABBREVIATIONS (IN ALPHABETIC ORDER)
AUS - Atypia of Undetermined Significance
FNA - Fine needle aspiration
FN - Follicular Neoplasm
FLUS - Follicular Lesion of Undetermined Significance
SFN - Suspicious For Follicular Neoplasm
SM - Suspicious For Malignancy
TBSRTC - The Bethesda System for Reporting Thyroid Cytopathology.
EDITORIAL/PEERREVIEW STATEMENT
To ensure the integrity and highest quality of CytoJournal publications, the review process of this manuscript was conducted under a double-blind model (the authors are blinded for reviewers and vice versa) through automatic online system.
References
- Cancer Res. 2014;74:2913-21.Projecting cancer incidence and deaths to 2030: The unexpected burden of thyroid, liver, and pancreas cancers in the United States.
- [CrossRef] [PubMed] [Google Scholar]
- Ann Saudi Med. 2003;23:408-9.Fine needle aspiration in the management of thyroid nodules: Experience at King Khalid National Guard hospital, Jeddah.
- [CrossRef] [PubMed] [Google Scholar]
- The Bethesda System for Reporting Thyroid Cytopathology, Difinitions, Criteria, and Explanatory Notes. In:
- Cancer. 2000;90:325-9.Fine-needle aspiration cytology of the thyroid: An appraisal.
- [CrossRef] [PubMed] [Google Scholar]
- Acta Cytol. 2016;60:397-8.The bethesda system for reporting thyroid cytopathology II.
- [CrossRef] [PubMed] [Google Scholar]
- Cancer. 2007;111:306-15.Fine-needle aspiration of thyroid nodules: A study of 4703 patients with histologic and clinical correlations.
- [CrossRef] [PubMed] [Google Scholar]
- Surg Pathol Clin. 2019;12:865-81.Pitfalls in thyroid cytopathology.
- [CrossRef] [PubMed] [Google Scholar]
- Arch Pathol Lab Med. 2019;143:1364-72.Trends in thyroid fine-needle aspiration cytology practices: Results from a college of American pathologists 2016 practice survey.
- [CrossRef] [PubMed] [Google Scholar]
- Diagn Cytopathol. 2016;44:737-41.The utility of cellient cell-blocks in low-cellularity thyroid fine needle aspiration biopsies.
- [CrossRef] [PubMed] [Google Scholar]
- Diagn Cytopathol. 2006;34:89-92.Utility of cell-blocks in the diagnosis of thyroid aspirates.
- [CrossRef] [PubMed] [Google Scholar]
- Cytopathology. 2009;20:103-8.Diagnostic pitfalls in the evaluation of fine needle aspiration cytology of the thyroid: Correlation with histopathology in 260 cases.
- [CrossRef] [PubMed] [Google Scholar]
- Arch Endocrinol Metab. 2016;60:367-73.Increasing diagnostic effectiveness of thyroid nodule evaluation by implementation of cell-block preparation in routine US-FNA analysis.
- [CrossRef] [PubMed] [Google Scholar]
- Cytopathology. 2018;29:525-30.Cell-block is a valuable adjunct to conventional smear for thyroid fine needle aspiration: 2395 cases with histological correlation.
- [CrossRef] [PubMed] [Google Scholar]
- Endocr Pract. 2016;22:622-39.American association of clinical endocrinologists, american college of endocrinology, and associazione medici endocrinologi medical guidelines for clinical practice for the diagnosis and management of thyroid nodules-2016 update.
- [CrossRef] [PubMed] [Google Scholar]
- Thyroid. 2006;16:55-60.The impact of assessing specimen adequacy and number of needle passes for fine-needle aspiration biopsy of thyroid nodules.
- [CrossRef] [PubMed] [Google Scholar]
- Diagn Cytopathol. 2016;44:676-81.Multiple squamous cells in thyroid fine needle aspiration: Friends or foes?
- [CrossRef] [PubMed] [Google Scholar]
- Cancer. 2005;105:71-9."Atypical" cells in fine-needle aspiration biopsy specimens of benign thyroid cysts.
- [CrossRef] [PubMed] [Google Scholar]
- Cytojournal. 2009;6:3.Hemosiderin laden macrophages and hemosiderin within follicular cells distinguish benign follicular lesions from follicular neoplasms.
- [CrossRef] [PubMed] [Google Scholar]
- Cancer Cytopathol. 2018;126:336-41.Thyroid FNA biopsies comprised of abundant, mature squamous cells can be reported as benign: A cytologic study of 18 patients with clinical correlation.
- [CrossRef] [PubMed] [Google Scholar]
- Pathol Res Pract. 2006;202:99-106.Massive squamous metaplasia of the thyroid gland-report of three cases.
- [CrossRef] [PubMed] [Google Scholar]
- Am Surg. 2014;80:811-6.False-negative results with the bethesda system of reporting thyroid cytopathology: Predictors of malignancy in thyroid nodules classified as benign by cytopathologic evaluation.
- [CrossRef] [PubMed] [Google Scholar]
- J Am Coll Surg. 2011;213:188-94. discussion 194-5Fine needle aspiration of the thyroid: Correlation with final histopathology in a surgical series of 797 patients.
- [CrossRef] [PubMed] [Google Scholar]
- Eur J Endocrinol. 2010;162:1107-15.Ultrasound-guided fine-needle aspiration of thyroid nodules: Stratification of malignancy risk using follicular proliferation grading, clinical and ultrasonographic features.
- [CrossRef] [PubMed] [Google Scholar]
- Ann Surg Oncol. 2012;19:45-51.Diagnostic accuracy of surgeon-performed ultrasound-guided fine-needle aspiration of thyroid nodules.
- [CrossRef] [PubMed] [Google Scholar]
- J Clin Endocrinol Metab. 1974;38:976-98.Malignant and benign neoplasms of the thyroid in patients treated for hyperthyroidism: A report of the cooperative thyrotoxicosis therapy follow-up study.
- [CrossRef] [PubMed] [Google Scholar]
- J Cytol. 2016;33:145-9.Cytomorphologic spectrum of lymphocytic thyroiditis and correlation between cytological grading and biochemical parameters.
- [CrossRef] [PubMed] [Google Scholar]
- Cytojournal. 2007;4:10.Lymphocytic thyroiditis-is cytological grading significant? A correlation of grades with clinical biochemical ultrasonographic and radionuclide parameters.
- [CrossRef] [PubMed] [Google Scholar]
- Endocr Pathol. 2014;25:12-20.Follicular-patterned afflictions of the thyroid gland: Reappraisal of the most discussed entity in endocrine pathology.
- [CrossRef] [PubMed] [Google Scholar]
- Surgery. 2011;150:1234-41.The impact of atypia/follicular lesion of undetermined significance on the rate of malignancy in thyroid fine-needle aspiration: Evaluation of the bethesda system for reporting thyroid cytopathology.
- [CrossRef] [PubMed] [Google Scholar]
- Cancer. 2009;117:298-304.Thyroid fine-needle aspiration with atypia of undetermined significance: A necessary or optional category?
- [CrossRef] [PubMed] [Google Scholar]
- Ann Surg Oncol. 2013;20:60-5.Management of thyroid nodules with atypical cytology on fine-needle aspiration biopsy.
- [CrossRef] [PubMed] [Google Scholar]
- Acta Cytol. 2011;55:518-25.Spectrum of risk of malignancy in subcategories of “atypia of undetermined significance”.
- [CrossRef] [PubMed] [Google Scholar]
- Diagn Cytopathol. 2012;40:410-5.Thyroid follicular lesion of undetermined significance: Evaluation of the risk of malignancy using the two-tier sub-classification.
- [CrossRef] [PubMed] [Google Scholar]
- Arch Pathol Lab Med. 2016;140:1318-22.The state of cell-blocks and ancillary testing: Past, present, and future.
- [CrossRef] [PubMed] [Google Scholar]
- Adv Anat Pathol. 2017;24:45-55.Cytopathology of follicular cell nodules.
- [CrossRef] [PubMed] [Google Scholar]
- Thyroid. 2009;19:1159-65.The bethesda system for reporting thyroid cytopathology.
- [CrossRef] [PubMed] [Google Scholar]
- Am J Clin Pathol. 2002;118:603-5. author reply 605-6Encapsulated follicular variant of papillary thyroid carcinoma.
- [Google Scholar]
- Am J Clin Pathol. 2015;144:850-7.Fine-needle aspiration diagnoses of noninvasive follicular variant of papillary thyroid carcinoma.
- [CrossRef] [PubMed] [Google Scholar]
- Hum Pathol. 2015;46:657-64.Invasion rather than nuclear features correlates with outcome in encapsulated follicular tumors: Further evidence for the reclassification of the encapsulated papillary thyroid carcinoma follicular variant.
- [CrossRef] [PubMed] [Google Scholar]
- Cancer Cytopathol. 2016;124:699-710.Young investigator challenge: The morphologic analysis of noninvasive follicular thyroid neoplasm with papillary-like nuclear features on liquid-based cytology: Some insights into their identification.
- [CrossRef] [PubMed] [Google Scholar]
- Thyroid. 2015;25:567-610.Revised American thyroid association guidelines for the management of medullary thyroid carcinoma.
- [CrossRef] [PubMed] [Google Scholar]
- Clin Endocrinol (Oxf). 2015;82:280-5.Detection rate of FNA cytology in medullary thyroid carcinoma: A meta-analysis.
- [CrossRef] [PubMed] [Google Scholar]
- Diagn Cytopathol. 2000;22:351-8.Cytologic diagnosis of medullary carcinoma of the thyroid gland.
- [CrossRef] [Google Scholar]
- Adv Anat Pathol. 2014;21:26-35.Update on the cytologic and molecular features of medullary thyroid carcinoma.
- [CrossRef] [PubMed] [Google Scholar]
- Appl Immunohistochem Mol Morphol. 2008;16:548-53.Relevance of immunocytochemistry on thin-layer cytology in thyroid lesions suspicious for medullary carcinoma: A case-control study.
- [CrossRef] [PubMed] [Google Scholar]
- Cytojournal. 2019;16:12.CellBlockistry: Chemistry and art of cell-block making. A detailed review of various historical options with recent advances.
- [CrossRef] [PubMed] [Google Scholar]
- Clin Surg. 2019;4:2510.CellBlockistry: Science of cell-block making as ancillary cytopathology component in the era of minimally invasive techniques with increasing role of molecular pathology.
- [Google Scholar]
- Cytojournal. 2021;18:10.CytoJournal monographs: First CMAS (CytoJournal monograph/atlas series) on science of cell-block making, titled “CellBlockistry 101 (Text book of cell-blocking science)”.
- [CrossRef] [PubMed] [Google Scholar]
- Available from: https://www.Avbioinnovation.com [Last accessed on 2022 Mar 17]AV BioInnovation.
- [Google Scholar]