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Abstract
Background: Cytological smear and cell block are commonly used to diagnose pleural fluid effusion. However, there is a paucity of information in the literature where a comparison between a cytological smear and a cell block with corresponding pleural biopsy has been done. This study aimed to evaluate the accuracy of cytological smears, cell blocks, and pleural biopsy for the diagnosis of malignant tumors. Material and Methods: In this cross-sectional study, analysis of successive pleural fluid samples received by the department was done. The sample was divided into equal halves of 5 ml each. One was used for conventional smear and the second was used for the preparation of cell block. The cell block was prepared by centrifuging the specimen of fluid at 2500 rpm for 15 min. A pleural biopsy was obtained by using Cope's pleural biopsy needle. Results: A total of n = 50 cases were included in the study. A total of n = 8 cases were diagnosed as malignant by cell smear and n = 4 cases were suspicious for malignancy. By cell block, n = 10 cases of malignancy were diagnosed and n = 1 case was suspicious for malignancy. By biopsy, n = 11 cases were diagnosed as malignant and n = 1 case was suspicious for malignancy. Out of the total, n = 2 cases were diagnosed as squamous cell carcinoma by biopsy; one case was diagnosed by cell block; and the other was reported as suspicious for malignancy. Conclusion: The study shows that cell blocks are complementary to the cell smear technique in over diagnosis and categorization of benign as well as malignant cells. The cell blocks were more useful in the diagnosis of malignancy because of better preserved architectural patterns as seen in corresponding histopathology sections. It, therefore, appears that the cell blocks are a perfect fit to bridge the cytology and histopathology.
Keywords: Cell block, cell smear, pleural biopsy, pleural effusion, pleural fluid cytology
How to cite this article: Introduction 
Cytological examination of serous fluids is of paramount importance not only in detecting cancer cells but also reveals information regarding various inflammatory conditions of the serous membranes, various bacterial, viral, and fungal infections, and parasitic infestations.[1] Cytological examination of fluids obtained from the serous cavities is among the most common tasks performed in the practice of cytopathology. The cytology is well established, making it valuable in the routine process of identification of a case of fluid effusion. The most common reason to submit an effusion to cytopathology is to determine whether it contains malignant cells.[2] Common causes of exudative pleural effusions are the metastatic disease of lymph nodes of the pleura/mediastinum. Lung cancers, breast cancers, and lymphomas were causes of pleural effusions in 75% of cases.[3] Malignant pleural effusions are found in 23.1% of cases of lung cancer.[4] Accurately diagnosing cells as either benign/malignant, reactive/mesothelial cells in serous effusions is a common diagnostic challenge. The lower sensitivity of cyto-diagnosis of effusions is mainly attributable to bland morphological details of cells, overcrowding, or overlapping of cells, cell loss, and changes due to different laboratory processing methods.[5] Most of the fluids received in the cytology laboratory contain blood clots or small bits of tissue from the lesion. While preparing the slide, they remain in the bottle and are not available for microscopy. Cell blocks are also particularly useful when samples are heavily admixed with blood. Good tissue fragments may be found in sections of the cell block because the fluid is first centrifuged.[6] The main advantage of the cell block technique is that cells resemble those seen in histology.[7] Apart from increased cellularity, better morphological details are obtained by the cell block method, which includes preservation of the architectural patterns like cell balls, papillae, and three-dimensional clusters, better nuclear and cytoplasmic preservation, intact cell membrane, and chromatin details. Other advantages, like multiple sections of the same material, can be obtained for special stains and immunohistochemistry.[8] The disadvantages of cell blocks that are more time is required for preparation and diagnosis, the samples are at risk of misplacement or loss during the process, and cell architecture may be altered in some cases when subjected to centrifuge at high speeds. Hence, we conducted this study where we compared the results obtained by cell block with the gold standard biopsy. The primary objective was to determine the efficacy of cell block in the diagnosis of various causes of pleural effusion, particularly malignant lesions.
Material and Methods The Institutional Ethical Committee permission was obtained for the study after following the due protocol for human research studies. Analysis of successive pleural fluid samples received by the department was done. A total of n = 50 cases were included in the study. All the details of patients, which included age and sex, were recorded. The fluids obtained were examined by the naked eye for physical characteristics and were divided into two halves of 5 ml each. One was used for conventional smear and the second was used for the preparation of cell blocks. The cell block was prepared by centrifuging the specimen of fluid at 2500 rpm for 15 min. The supernatant fluid was discarded and a cell button was formed. To this, two to three drops of plasma, thromboplastin, and calcium chloride were added so as to allow to form a clot. The cell button along with the clot formed is fixed with 10% buffered formalin for 24 hours. The cell button was then wrapped in filter paper and processed in a tissue processor. Following this, the cell block was prepared after embedding it in paraffin medium. The sections were obtained and stained with hematoxylin and eosin special stains such as PAS were used when necessary. Pleural biopsy: First confirmation of pleural effusion was done by inserting a needle into the pleural cavity. After this, at an appropriate point, a small incision was made with an adequate quantity of lignocaine introduced. A cope's pleural biopsy needle with a trocar and cannula was introduced into the pleural space by a clockwise and counterclockwise twisting motion. The withdrawal of the trocar was seen with a trickle of fluid through the cannula, the biopsy needle was introduced through the cannula and three bits of pleural tissues were obtained from the inferior and lateral aspects. Superior aspects are avoided to spare the intercostal bundle. The samples were sent for histopathology examination with 10% formalin in saline solution.
Results Of the n = 50 cases included in the study, 60% were males and 40% were females. The male to female ratio was 3:2. The males in the study who were in the age group of 31–40 years were 20% and the minimum age was 19 years and the maximum age was 62 years. The mean age of the males in the study was 49.5 ± 3.5 years. In the female cases, the mean age was 41.5 ± 2.5 years and 10% of cases were from the age group of 21–30 years. The minimum age was 20 years and the maximum age was 61 years. The common symptoms at the time of admission to the hospital were breathlessness (48%), fever (20%), cough (20%), and chest pain (12%) [Table 1].
In conventional smears, 16% of cases were diagnosed as malignant, 4% were suspicious for malignancy, and 80% were indicative of non-malignancy. Moderate cellularity was found in most of the cases by conventional smear and cell block. The architectural pattern of cell clusters, cell balls was commonly found in cell block preparations [Figure 1]C and [Figure 1]D. In cell smears, pauci cellularity was shown comparatively in many cases, with the singly scattered cell being the pattern [Figure 1]A and [Figure 1]B. Rich cellularity was found in 32% of cases of cell block as compared to 24% by conventional smears [Table 2].
Figure 1: (A) 40X H and E smear showing tumor cells arranged in an acinar pattern (Adenocarcinoma); (B) 40X GIEMSA smear showing tumor cells in the monotonous population (small cell carcinoma); (C) 40X H and E biopsy section showing tumor cells arranged in an acinar and glandular pattern (Adenocarcinoma); (D) 40X H and E biopsy section showing squamous cells with atypical features along with keratin pearls (Squamous cell carcinoma); (E) 40X H and E cell block pericellular lacunae (Adenocarcinoma); (F) 40X H and E glandular pattern of tumor cells (Adenocarcinoma)Out of n = 50 cases in the study, the diagnostic yield for malignancy was greater with the pleural biopsy as compared to the cell block technique. N = 1 case which was reported as benign by the cell block method was found to be malignant. These cases were diagnosed as nonspecific inflammation in the cell block method, probably due to a lack of representative cells in the samples. Around 4% of cases of tuberculosis were also reported as nonspecific inflammation by cell block, which was diagnosed as tuberculosis by biopsy [Table 3].
A total of n = 8 cases were diagnosed as malignant by cell smear and n = 4 cases were suspicious for malignancy [Figure 1]E and Figure 1]F. By cell block, n = 10 cases of malignancy were diagnosed and n = 1 case, suspicious for malignancy. By biopsy, n = 11 cases were diagnosed as malignant and n = 1 case was suspicious for malignancy. Out of the total n = 2 cases diagnosed as squamous cell carcinoma by biopsy one case was diagnosed by cell block and the other was reported as suspicious for malignancy [Table 4].
Discussion Pleural effusion is the accumulation of fluid in the pleural cavity that exceeds the physiologic amounts of 10–20 ml. Recent studies carried on an Indian population with pleural effusion, revealed that tuberculous pleural effusion (TPE) occurs in approximately 23.5% of patients with tuberculosis.[9] TPE is the leading cause of pleural effusions in developing countries across the world.[10] In this study, pleural effusions were studied by using a comparative approach of routine cytosmears, cell block technique, and pleural biopsy methods. The basic idea was to analyze the efficacy of cell block versus the biopsy technique which is considered as standard in pathological diagnosis. The cell block technique is now gaining wider acceptance with effective utilization in effusion cytology and fine-needle aspiration cytology.[11],[12] Oygluso et al., reported conventional cytology sensitivity to be a mere 44.5% and specificity 95.7%, with PPV of 98.7% and NPV of 20%.[13] The cell block preparation in this study was done using 10% alcohol-formalin fixative. It increases the cellularity and gives the morphological details of the cells. Another advantage is that multiple sections can be obtained by the Cell Block (CB) method for the special stains and immunohistochemistry studies. In this study by cytosmears, n = 76% of cases were diagnosed as chronic nonspecific inflammation and 8% of cases diagnosed as suspicious for malignancy, and 16% of cases were given as positive for malignancy. By the cell block method, we found 32% of cases were TPEs, malignant effusion in 10% of cases and nonspecific inflammation in 48% of cases. While by using biopsy 24% of cases were diagnosed as malignant effusions. 36% of cases were diagnosed as TPEs and 40% of cases were diagnosed as nonspecific inflammation. Sujathan et al; in their study by cell block preparation, found that out of n = 85 samples of pleural fluid samples n = 63 (74.12%) were inflammatory and n = 21 (25.88%) were malignant.[14] Conventional smear cytology is a very easy technique; however, the main area of concern is its ability to discriminate malignant cells from reactive mesothelial cells.[15],[16] Apart from that, the technique of preparation and staining has also impacted the ability to diagnose the lesions. Bad fixations, artifacts, and poor staining are the problem areas. In recent years, many improvements to cytological smears have been made. Monolayer preparations ThinPrep® processor, AutoCyte PREPTM system, or other similar processors have been used. They prevent air drying of specimens and reduce the artifacts and increase the cellularity by reducing background material. Cytological sensitivity has increased considerably.[17] Basnet et al., have shown that the diagnosis of neoplastic lesions by cell block technique is superior to smear both in terms of rapid identification and staging of tumor.[18] In this study, we have found that biopsy results have found 4% more cases of malignancy as compared to the cell block technique. The diagnosis of adenocarcinoma in this study was done in 10% of cases by cell block, whereas the biopsy found an additional 2% of cases of adenocarcinoma which was missed by the cell block. Similarly, 2% additional cases of squamous cell carcinoma were detected by the biopsy technique as compared to the cell block technique. It has been found that in some cases the biopsy specimens are contaminated by non-neoplastic cells and can hamper diagnosis. In such cases, cytological specimens are useful as the contamination by non-neoplastic cells is lesser in cytology. Cytology has a greater opportunity than needle biopsy to retrieve malignant cells in the presence of malignant deposits.[19] Studies have shown that the cell block method increases the final diagnostic accuracy and that the diagnostic yield can vary from 10% to 15%.[12],[20],[21],[22] Alwahaibi et al., in a similar study comparing the accuracy of cell smear, cell block, and tissue biopsies, they found out of n = 70 cases, cytological smear showed 100% sensitivity while CB showed 98.4% sensitivity.[17] Therefore, we found that the cytological smear and cell block are sensitive and accurate in the detection of malignant tumors. However, in some cases, an additional corresponding tissue biopsy may be required for re-evaluation.
Conclusion The study shows that cell blocks are complementary to the cell smear technique in the diagnosis and categorization of benign as well as malignant cells. The cell blocks were more useful in the diagnosis of malignancy because of their better preserved architectural patterns as seen in the corresponding histopathology sections. It, therefore, appears that the cell blocks are a perfect fit to bridge the cytology and histopathology.
Acknowledgments
The authors thank the Dept of Pathology, Kamineni Institute of Medical Sciences, Narketpally, Telangana State, India, for their support in the conduction of this study.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References 
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/joc.joc_91_21
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