| Abstract|| |
Context: Fine-needle aspiration cytology is considered the gold standard screening test in the evaluation of a thyroid nodule. We studied whether cell block cytology can be used in addition to conventional smears for the evaluation of tissue from fine-needle aspirations or fluid aspirations and also compared it with histopathological diagnosis. Aims: The primary aim of this study was to know the utility of cell blocks in the diagnosis of thyroid lesions. Settings and Design: This was a prospective observational study conducted from June 2018 to September 2020 at a tertiary Care Hospital in Eastern India. Ethical approval was obtained from the Ethics Committee of the institution. Patients above 18 years who presented with goiter were included in the study. Thirty patients were enrolled in the study after informed consent. Methods and Material: Smears prepared from the aspirates were stained with Leishman-Giemsa (LG) and Pap stain. The remnant from the needle hub was transferred to a sterile container. Cell blocks were prepared from the remnants. Smears were scored based on cell obscuration by blood, cellularity, cell degeneration, and cell architecture. The results were compared with histopathology. Statistical Analysis Used: Data were recorded using Microsoft Excel. Descriptive statistics, frequency, and proportion were used to describe demographic variables. Results: The majority of the patients (23.3%) were in their third decade of life, followed by 16.7% of the patients in their fourth and fifth decades. The patient age ranged from 25 to 80 years, with a mean age of 50.83 years and a standard deviation of 16.72. The largest number of patients were females accounting for 80% (24/30) of the total participants. The majority of the patients (36.7%) (11/30) had thyroid gland enlargement for a period of 15 days to three months. 14% of the participants were not able to recall its duration. The majority (60%) (18/30) had left lobe lesions, followed by 33.3% (10/30) who had right lobe lesions, and 6.7% (2/30) who had bilateral lobe swelling. The mean size of the lesion was 2.84 cm. 50% were found to be Bethesda II lesions, while 13.3% were Bethesda IV, and 36.7% were found to be Bethesda VI lesions. The cell block score (7) was found to be better compared to Fine Needle Aspiration Cytology (FNAC) (4.7). Tissue Coagulum Clot and Clot Scrape methods were found to yield better results compared to the Cytocentrifuge method. The P value was found to be significant (<0.001). Conclusions: Cell blocks were found to improve the cell morphology compared to FNAC alone and can be used as an adjunct to FNAC in the diagnosis of various thyroid lesions.
Keywords: Cell block, fine needle aspiration cytology, goiter, thyroid nodule
|How to cite this article:|
Jambhulkar M, Bhatia JK, Singh SK. Correlation between fine-needle aspiration cytology, cell block cytology, and histopathology in the diagnosis of thyroid lesions. J Cytol 2022;39:91-7
|How to cite this URL:|
Jambhulkar M, Bhatia JK, Singh SK. Correlation between fine-needle aspiration cytology, cell block cytology, and histopathology in the diagnosis of thyroid lesions. J Cytol [serial online] 2022 [cited 2022 Dec 4];39:91-7. Available from: https://www.jcytol.org/text.asp?2022/39/3/91/352994
| Introduction|| |
The prevalence of thyroid nodules ranges from 4% to 10% in the general adult population and from 0.2% to 1.2% in children. The majority of these nodules are benign, and only 5% to 30% are malignant. Ultrasonography and Fine-needle aspiration cytology (FNAC) are the main tools used by the clinician to decide whether surgical excision of a thyroid nodule is warranted or not. FNAC is considered the gold standard screening test in the evaluation of a thyroid nodule. It is cost-effective and a safe procedure. Nevertheless, like any other test, fine needle aspiration has its limitations and diagnostic pitfalls. These limitations include false negative and false positive results and a proportion of fine-needle aspiration results that are not obviously benign or malignant and fall into the indeterminate or suspicious group. The reported pitfalls are mostly related to specimen adequacy, sampling techniques, the skills of the physician performing the aspiration, the experience of the pathologist interpreting the aspirate, and the overlapping cytological features between some benign and malignant thyroid lesions.
In routine cytological practice, the cell morphologic changes in smears are not always obvious. Sometimes judgment is difficult; therefore, the cell block may give a better presentation of detailed architectural features. Also, implementing histochemical or immunocytochemical staining has been a useful adjunct for establishing a more definitive diagnosis. Sometimes cytology does not provide sufficient information, and the risk of false negative or undetermined diagnosis exists.
When cellular level alterations alone are sufficient for a diagnosis, a minimal sample is acceptable. For many diagnoses, however, it may be necessary to be able to recognize the larger-scale alterations in tissue architecture or to study biochemical and molecular characteristics of the cells; cell blocks fulfill this need. The use of cell blocks has been advocated in a few studies, while some have found no utility in thyroid aspirates.,
The aim of this study was to evaluate the importance of cellblock in combination with FNAC in the diagnosis of different thyroid lesions and correlate it with histopathological findings.
| Subjects and Methods|| |
This was a prospective observational study conducted from June 2018 to September 2020 at a tertiary Care Hospital in Eastern India. Ethical approval was obtained from the Ethics Committee of the institution. Patients above 18 years who presented with goiter were included in the study. Thirty patients were enrolled in the study after informed consent.
FNAC was performed and Leishman-Giemsa (LG) and Pap-stained slides were prepared from aspirates. FNAC slides were reported as per the Bethesda system for reporting thyroid cytology, 2017.
Needle rinses were done with saline in a clean container for the preparation of cell blocks from the material left in the hub of the needle. A concentrated cell button was prepared by centrifugation at 2400 revolutions per minute (RPM) for five minutes. The button was processed for histopathology. In case the specimen was not enough for a button, the tissue clot coagulum method was used. The remnant was added into an empty container and allowed to clot.
Then formalin was added for fixation. The clotted material was transferred into filter paper, folded and shifted into metal cassettes, and processed like a histopathology specimen.
Cytology and cell block
Cytomorphology of the two processing techniques (conventional smear and cellblock) was scored using the Mair et al. scoring system for assessing the quality of the slides into four categories: background obscuring material, degree of cellular degradation, cellularity, and architectural and cellular arrangement. The changes were categorized into marked, moderate, and minimal. [Table 1] shows the Mair et al. scoring system and the scores. Cytomorphological scores were compared between cytology smears and cell blocks. Mean, median, and standard deviation were calculated. The cytodiagnosis was also compared.
|Table 1: Shows Mair et al. scoring system and the scores for obscuring background, cellular material, cellular degeneration, architecture, and cellular arrangement|
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The diagnosis was then correlated with the histopathological diagnosis in the cases in which the specimen was available.
Data were analyzed using Microsoft Excel. Categorical variables were expressed as the number of patients and percentage of patients. Continuous variables were expressed as Mean, Median, and Standard deviation and compared using Wilcoxon Sign Rank Test. The statistical software Statistical Package for the Social Sciences (SPSS) version 20 was used for the analysis. An alpha level of 5% was taken, and P values less than 0.05 were considered significant.
| Results|| |
A total of 30 patients with thyroid gland enlargement were enrolled in this study. The patient age ranged from 25 to 80 years, with a mean age of 50.83 years and a standard deviation of 16.72. The majority of the patients (23.3%) (7/30) were in their third decade of life, followed by 16.7% (5/30) of the patients in their fourth and fifth decades. Females accounted for 80% (24/30) of the total participants. In (36.7%) (11/30) of the patients, the duration of enlargement of the thyroid was 15 days to 3 months. 60% (18/30) had left lobe lesions, 33.3% (10/30) had right lobe lesions, and 6.7% (2/30) had bilateral lobe swelling. The minimum size of the lesion was 1 cm, while the maximum size was 4 cm. The mean size of the lesion was 2.84 cm. (standard deviation (SD): 0.88 cm).
Cytomorphology of the two processing techniques (conventional smear and cellblock) was assessed using the Mair et al. scoring system.
The categories used were background obscuring material, degree of cellular degradation, cellularity, and architectural and cellular arrangement.
The slides from the two methods were examined for obscuring material which was mostly blood and staining artifacts. 33.3% (10/30) of the cases on modified cell block had minimal background obscuring material as opposed to 16.7% (5/30) on conventional smears. Conventional smears had marked background obscuring in more than half of the cases (53.3%) (16/30), unlike (30%) (9/30) in cell block cases. Both conventional smears and cell block were comparable on moderate background obscuring, which was 30% (9/30) and 36.7% (11/30), respectively.
Cell blocks showed marked cellularity in 43.3% (13/30) as compared to 20% (6/30) in conventional smears. Moderate cellularity was scored in 40% (12/30) of conventional smears. Minimal cellularity was seen in 40% (12/30) and 30% (9/30) in conventional smears and cell blocks, respectively.
In addition to cellularity and background, the degree of cellular degeneration was also evaluated using the Mair et al. scoring system. However, the scores were comparable across all categories on both modified cell block and conventional smears as shown, i.e., there was not much difference in cellular degeneration in conventional smears and cell blocks.
The architectural pattern and the cellular arrangement were evaluated on both methods. 40% (12/30) of the modified cell blocks were categorized to have marked architectural and cellular arrangement as compared to 20% (6/30) on conventional smears. Architectural patterns and cellular arrangement were better appreciated on cell blocks [Figure 1].
|Figure 1: Cytomorphologic features between FNAC conventional smears and Cell Block as per the Mair et al. scoring system|
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Conventional smears were reported using the Bethesda System of Reporting Thyroid cytopathology, 2017.
Results compared with histopathology specimen reports. 50% of the cases were found to be benign.
Cytomorphological scores were compared between cytology smears and cell blocks. Mean, median, and standard deviation were calculated. The P value was found to be significant (<0.001).
A comparison of cell morphology scores between FNAC and Cell Block and P-Value is given in [Table 2].
|Table 2: Comparison of cell morphology scores between FNAC and Cell Block and P value|
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The mean score in cell morphology was found to be 7 in Cell Block as compared to 4.67 in the case of FNAC.
Colloid goiters were reported in 12 (40%) of the paucicellular conventional smears, which were found to be moderately cellular in cellblock cases, out of which in four cases specimens were received and confirmed on histopathological examination. Four (13%) of the paucicellular (2/30) to moderately cellular (2/30) cytology smears were diagnosed as papillary carcinoma thyroid and were found to be cellular on cell block 4 (13%) as well as specimens 4 (13%).
Cases of colloid goitre, [Figure 2]a, [Figure 2]b, [Figure 2]c Hashimotos thyroiditis [Figure 2]d, [Figure 2]e, [Figure 2]f papillary carcinoma [Figure 3]a, [Figure 3]b, [Figure 3]c, follicular carcinoma [Figure 3]d, [Figure 3]e, [Figure 3]f, medullary carcinoma [Figure 4]a, [Figure 4]b, [Figure 4]c, anaplastic carcinoma, [Figure 4]d, [Figure 4]e, [Figure 4]f on FNAC, Cell Block, and Histopathology are presented.
|Figure 2: (a-f): (a) Conventional smear showing paucicellular smear with benign thyroid follicular cells and colloid (b) cell block shows benign thyroid follicular cells with colloid. (c )Histopathological specimen shows benign colloid filled thyroid follicles. (d) Fine needle aspiration smear in Hashimoto's thyroiditis shows paucicellular smear with a few lymphocytes infiltrating thyroid follicular cells and obscuration (d) Cell block with follicles and lymphocytes and confirmed on histopathology (f) showing follicles with Hurthle cell change infiltrated by lymphocytes|
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|Figure 3: (a-f): (a)Fine needle aspiration smear papillary carcinoma show neoplastic thyroid cells forming ill formed papillae surrounded by blood. (b)Cell block shows thyroid follicular cells in papillary architecture with nuclear features. (c)Histopathology confirmed the diagnosis . (d) Conventional smear follicular neoplasm show follicular epithelial cells in sheets, (e) cell block shows thyroid follicles lined by neoplastic cells, confirmed as Follicular carcinoma in histopathology (f)|
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|Figure 4: (a-f): (a) FNAC smear showing plasmacytoid cells (b) Cell block of Medullary carcinoma with plasmacytoid cells (c) Medullary carcinoma confirmed on histopathology (d) FNAC showing atypical pleomorphic cells of anaplastic carcinoma on FNAC (e) Cell block showing malignant spindle cells suggestive of Anaplastic carcinoma thyroid (f) Anaplastic carcinoma was confirmed on Histopathology|
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No cases in our study were better diagnosed on FNAC than the cell blocks.
Two cases of fine-needle aspiration cytology smears were found to have atypical cells, diagnosed as suspicious for malignancy, out of which one (3.3%) was anaplastic and one case (3.3%) was medullary carcinoma on the cell block. Three cases of Follicular neoplasm (2/30 paucicellular, 1/30 moderately cellular) (10%) and three cases (10%) of Hashimoto's Thyroiditis (2/30 paucicellular, 1/30 moderately cellular) were seen in fine-needle aspiration and cell block and confirmed on histopathological examination of specimens.
Five cases with a variable diagnosis on FNAC were modified on the cell block and later confirmed on histopathology specimens. One case (3.3%) diagnosed as papillary carcinoma on cytology smears was found to be medullary carcinoma on the cell block and confirmed later on a histopathological specimen. Two cases were diagnosed as nodular colloid goiter 6.7% (2/30) on fine-needle aspiration smears were found to be papillary carcinoma 6.7% (2/30) on the cell block and confirmed on histopathology specimens. One case was diagnosed as follicular neoplasm 3.3% (1/30) on smears and was found to be papillary carcinoma 3.3% (1/30) on the cell block and histopathology. One case diagnosed with Hashimoto's Thyroiditis 3.3% (1/30) on smear was found to be Follicular Lymphoma 3.3% (1/30) on the cell block and confirmed on histopathology. The cases where diagnosis was modified using cell block in addition to FNAC are presented in [Table 3].
|Table 3: Cases where the diagnosis was modified using cell block in addition to FNAC|
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A significant score difference was noted in benign lesions compared to malignant lesions suggesting that cell morphology improved more in the cell block in benign lesions compared to malignant lesions.
| Discussion|| |
FNAC is a gold standard in the initial screening of thyroid nodules and plays an important role in triaging thyroid lesions. Despite the proven clinical importance of thyroid FNAC, it still has limitations related not only to inadequate sampling but also to limited cellularity of the obtained sample.
Cell block cytology is a technique used in cytopathology for the evaluation of tissue from fine-needle aspirations or fluid aspirations. The paraffin blocks prepared from any suspension of cells or fluids are suitable for sectioning, staining, and microscopic study. Cells are concentrated by centrifugation or filtering techniques resulting in aggregation being processed as if it were a solid specimen of tissue.
The use of cell blocks has been widely advocated in the diagnostic work-up of patients with masses amenable to fine-needle aspiration since they provide diagnostic architectural information which complements fine-needle aspiration smears.
Adequate cell blocks enable subsequent tests and can offer a definite diagnosis as well as information critical for focused treatment strategies.
These techniques frequently help in the final categorization of the lesion and the identification of therapy alternatives. Fine needle aspiration with cell block is not only less invasive, but is also less expensive since it avoids needless thyroidectomy. Cell blocks can be stored for future diagnostic and research reasons while still preserving the original smears. Another advantage is that new microwave processing techniques may be utilized for tiny biopsies and cell blocks, reducing turnaround time in emergency instances.
Different techniques of cell block preparation employ various media for rinsing, transporting, and fixing specimens. Neutral buffered formalin is considered the universal fixative.
Various methods of cell block preparation are in use, of which the Plasma thrombin method is the most common cell block technique. The cell block is made from a pellet of centrifuged cell suspension by enmeshing the cellular components in a clot with plasma and thrombin. The sample is centrifuged for 10 minutes at 1,650 RPM. The supernatant is decanted after centrifugation. About 0.5 mL of plasma is added to the sediment, along with two drops of 3% aqueous eosin, which is vortexed quickly. The solution is immediately stirred after 0.25–0.5 mL of reconstituted thrombin is introduced. Within 30–60 seconds, a clot is developed. The clot is placed on a formalin-laced cassette with a label. The material is then regularly processed.
Another commonly used method is the Tissue coagulum clot method. This technique permits a clot to develop in the lumen of the tiny needle aspiration tip. The clot is then transferred straight to formalin for fixation. The method prevents the loss of diagnostic material. The clot is partially air-dried on filter paper, mostly to guarantee that the coagulum remains solid and that the cellular components are not distributed in a liquid media. The specimen is then wrapped in tissue paper and placed in a cassette with a formalin container. The material is subsequently regularly processed in the histology laboratory.
In our study, a total of 30 patients were evaluated. The age of patients ranged from 25 to 80 years, with a mean of 50.83 years and a standard deviation of 16.72 years. This age range and mean incidence is slightly higher as compared with the study done by Gupta et al. who found that the age range was from 22 to 58 years with a mean age of 38.7 years. The majority of the patients (23.3%) were in their third decade of life, followed by 16.7% of the patients in their fourth and fifth decades.
The majority of the patients (36.7%) (11/30) had thyroid gland enlargement for a period of 15 days to three months. 14% (4/30) of the participants were not able to recall its duration.
The majority of the participants in this study were female, accounting for 80% (24/30) of total participants with a male to female ratio of 1:4. This finding was slightly lower in a study conducted by Khattak et al. in a similar study, in which they found that 73% of females were suffering from thyroid lesions compared to 27% of males. The majority (60%) (18/30) had left lobe lesions, followed by 33,3% (10/30) who had right lobe lesions and 6.7% (2/30) who had bilateral lobe swelling. The size of the lesion ranged from 1 to 4 cm, with a mean size of 2.84 cm.
In the present research, 70% (21/30) of the paucicellular aspiration smears were found to be moderately cellular to cellular on the cell block. Two cases with atypical cells on aspiration smears diagnosed as suspicious for malignancy were found to be anaplastic and medullary carcinoma, respectively. Classical nuclear features of papillary carcinoma were better appreciated on cell block compared to cytology smears. False positive cases found on aspiration smears were found to be different on the cell block and histopathological diagnosis. Cellular features were enhanced in cell blocks compared to aspiration smears. Scoring was done on FNAC, and Cell block slides as per Mair et al. ranged from 0–2 based on cellularity, obscuration, degeneration, and cell architecture. Cell block score was found to be higher compared to FNAC. Statistical analysis revealed a significant P value <0.001.
More than half (53.3%) (16/30) of the conventional smears samples had marked obscuring background, while only (30%) (9/30) were reported to have marked obscuring background on cellblock sections. The main background obscuring material was blood because the thyroid gland is a highly vascular organ. However, 33.3% (10/30) of cellblock cases had a clear background (minimal obscuring background) as compared to 16.7% (5/30) of conventional cases. Cellularity was marked in 43,3% (13/30) of the cell block cases compared to 20% (6/30) of FNAC smears. Marked cellularity in cell blocks could be due to the presence of clots in the needle hub, which trap cells that were removed in cellblock preparation. This agrees with Kshatriya and Santwani. who showed that the cell block method allows the recovery and processing of minute amounts of cellular material. In this study, the degree of degradation was comparable in both techniques, with a minimal degradation rate of 66.6% (20/30) and 63.3% (19/30) in conventional and cell block cases, respectively. This minimal cellular degradation which was more than half of all cases in both the methods, was achieved because samples were fixed immediately after collection. This result agrees with Bista, who found that cellular degeneration and trauma were less appreciated in cell block sections which scored more than the smears cytology. Khan et al. also agreed that degeneration of cells in the cell block samples may be attributed to a delay in immersing the cell block specimen into fixative immediately after collection. In their study, the material for cell block was aspirated after 3 to 4 times of the aspirations for the conventional FNAC and this may have contributed to a more traumatized and poorly preserved specimen. Cell block showed 40% (12/30) marked architecture and cellular arrangement compared to 20% (6/30) in conventional smears. 46.7% (14/30) had a minimal architectural arrangement on conventional smears as compared to 33.3% (10/30) in the cell block. This agrees with Thapar et al., who concluded that the cell block technique not only increased the positive results but also helped to demonstrate better architectural patterns, which could be of great help in making the correct diagnosis of the primary site. The cell block technique was also useful for special stains and immunohistochemistry and can give morphological details by preserving the architectural patterns.
In this research, 50% were found to be Bethesda II lesions, while 13.3% were Bethesda IV, and 36.7% were found to be Bethesda VI lesions. This compares very well with Popoveniuc and Jonklas., who documented that 70% of all thyroid FNAC were reported as benign.
In our study, overall cell block was contributory to the diagnosis of 16% (5/30) cases which was more compared to Padmaja, who showed in her study that cell block aided in the diagnosis of 6% cases of thyroid lesions.
Cell block should be considered as an adjunct test to the conventional smear on thyroid FNA cytology.
The limitation of the study was a small sample size.
| Conclusion|| |
Cell block material facilitates diagnosis by increasing the diagnostic yield of the specimen and helps reduce repeat FNAC procedures. It affords additional information helpful in confirming and establishing the diagnosis of thyroid lesions by improving cellularity, maintaining cellular architecture, removal of obscuration factors like blood, and the ability to perform immunohistochemistry in confirmation of diagnosis.
The cell block technique could be utilized as a cost-effective diagnostic tool in the armamentarium of diagnostic work-up in the patients with thyroid lesions.
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Conflicts of interest
There are no conflicts of interest.
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Dr. Jasvinder K Bhatia
Department of Pathology, Command Hospital Eastern Command, Kolkata, West Bengal - 700 027
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3]