Flow cytometry as an adjunct to cytomorphologic analysis of serous effusions

Clinical and cytological characteristics of serous effusions in 69 cases of lymphoma patients

BACKGROUND

To explore the value of cell morphology, immunophenotype, and gene alterations of serosal effusion in the diagnosis of lymphoma.

METHODS

Serosal effusion of 69 cases of lymphoma patients were collected, including 36 cases with malignant effusion and 33 cases with nonmalignant effusion. Ordinary cytology, liquid-based cytology, cellblock, and immunocytochemical staining were performed in each case, some cases were detected by fluorescence in situ hybridization for C-MYC, BCL2, and BCL6 gene translocations. T/B cell ratio in malignant and nonmalignant serosal effusions was analyzed and compared by flow cytometry (FCM) and immunohistochemical (IHC), respectively. The prognostic value of serous effusion in diffuse large B-cell lymphoma (DLBCL) was investigated and another 20 DLBCL cases without effusion were successively selected as control.

RESULTS

The number of naive lymphocytes, apoptotic bodies, and mitotic figures were more common in malignant effusions compared with nonmalignant effusions (p < .01). The top three lymphomas in malignant effusion were DLBCL (19/36, 52.8%), mantle cell lymphoma (MCL) (4/36, 11.1%, 3 blastoid variant) and high-grade B-cell lymphoma (HGBL) (4/36, 11.1%). T/B cell ratio by FCM analysis ranged from 0.00 to 0.55 (mean 0.084) in malignant effusion, and 2.58 to 984.00 (mean 249.9) in nonmalignant effusion. The difference was significant (p = .017). The T/B cell ratio by IHC analysis ranged from 0.02 to 3.00 (mean 0.200) in malignant effusion, and 2.00-100.00 (mean 34.10) in nonmalignant effusion. The difference was significant (p = .017). In the effusions involving DLBCL, most effusions were present at the time of diagnosis (57.9%); single pleural effusions were more common (36.8%). The median overall survival times of patients with malignant effusion, nonmalignant effusion and DLBCL without serous effusion were 11, 17, and 23 months respectively (p = .04). Three patients of HGBL died, and the overall survival times were 5, 8, and 9 months, respectively.

CONCLUSIONS

The cytomorphological characteristics combined with immunophenotype, FCM, gene rearrangement, and other tests can diagnose and classify patients with effusion as the first symptom. The T/B cell ratio is less than 1 by FCM or IHC suggesting a malignant serosal effusion. The presence of malignant effusion in DLBCL patients is an important clue for poor prognosis.

Flow cytometry, molecular analysis, and other special techniques (in Serous Fluid Cytopathology)

Morphological and architectural pattern evaluations play a major role in the rpretation of hematopoietic neoplasms. However, confirmation of diagnosis, classification, prognosis, and risk stratification are highly dependent on the utilization of multiple ancillary studies. The importance of these ancillary studies increases in evaluating serous fluid samples, as these samples lack architecture and patterns. Likewise, the morphology can be disturbed by sample preparation. The most common ancillary studies utilized are flow cytometry, immunohistochemistry for immunophenotyping, Fluorescent In Situ Hybridization (FISH), cytogenetics for structural and gene rearrangements, and molecular studies for mutational analysis. Among them, flow cytometry analysis is the handiest test to perform with high diagnostic yield on serous fluid specimens. In this article we will discuss the use, caveat, and role of the most common ancillary studies on serous fluid specimen evaluation. This review article will be incorporated finally as one of the chapters in CMAS (CytoJournal Monograph/Atlas Series) #2. It is modified slightly from the chapter by the initial authors (Choladda Vejabhuti, MD and Chung-Che (Jeff) Chang, MD, PhD) in the first edition of Diagnostic Cytopathology of Serous Fluids.

Clinical application of an algorithm to screen for malignant cells in body fluids using an automated hematology analyzer

INTRODUCTION

The detection of malignant cells in body fluids (BF) with an automated hematology analyzer has been proposed as an alternative to morphological examination owing to its various advantages; however, its limitations have also been highlighted. In this study, we devised a practical algorithm to screen for malignant cells in BFs using an automated hematology analyzer.

METHODS

A total of 558 BF samples, including 232 cerebrospinal fluid (CSF) samples and 326 non-CSF samples, were consecutively collected. Thereafter, the results obtained using the BF mode of Sysmex XN-350 (Sysmex, Kobe, Japan) were compared with the cytological diagnosis. A cutoff was also established to screen for malignant cells using receiver operating characteristic (ROC) curve analysis based on the final clinical judgment.

RESULTS

The automated hematology analyzer showed a moderate correlation or good agreement with the existing cytological diagnosis. Further, of the ROC curves for detecting malignant cells, the absolute value of highly fluorescent cells on BF (HF-BF) in total body fluids showed the highest area under the curve (0.85 [95% confidence interval 0.82-88], p < .0001, Youden index >7×10⁶ /L, sensitivity 93%, and specificity 65%).

CONCLUSION

An automated hematology analyzer could function as a complement to cytological examination. We propose a practical and comprehensive algorithm for cytological examination that requires low- and high-resolution microscopy based on the absolute value of HF-BF in BF samples suspected of malignancy. This algorithm can more usefully detect malignant cells while taking advantage of the automated analyzer and cytological examination.

Case study-based systematic review of literature on lymphoma-associated cardiac tamponade

This study aimed to compile all the relevant studies of patients presenting with pericardial tamponade before or after diagnosis of lymphoma, describe the clinical presentations of patients with lymphoma and cardiac tamponade, and assess the difference in overall survival based on the timing of cardiac tamponade diagnosis.

A comprehensive search strategy was conducted in the following databases: PubMed and Cochrane Library, using the following keywords: Lymphoma AND Cardiac Tamponade. The criteria for eligibility included cases with a confirmed diagnosis of lymphoma and cardiac tamponade, human studies, and publications in English language. The statistical analysis was performed using IBM Statistical Package for Social Sciences (SPSS) version 20. We included 48 research articles (n = 52 cases) with adequate reporting of measured outcomes. The median age of the patients was 52 (9–94) years. Only 6 patients were noted to have primary cardiac lymphoma, while the majority of cases were considered to have secondary cardiac lymphoma (88.5%). According to the data on the type of lymphoma reported through cytology and immunohistochemistry, 49 patients were diagnosed with non-Hodgkin lymphoma, and of these cases the most common subtype was large B-cell lymphoma (42.9%). Overall, the average duration of illness was 14 ± 23 days. A total of 13 patients had distant heart sounds, 12 cases were noted to be hypotensive, and 13 subjects were found to have increased jugular venous pressure.

Our retrospective study demonstrated that most patients presented with pericardial tamponade after lymphoma diagnosis, and those were mostly secondary cardiac lymphoma of the non-Hodgkin type with large B-cell as the most common subtype. Dyspnoea, oedema, and constitutional symptoms were the most common presenting signs. The median overall survival of patients with lymphoma and cardiac tamponade is 4 months, with no significant difference in mortality in the presentation timing before and after the diagnosis of lymphoma.

Triaging of pleural effusion cytology specimens for ancillary flow cytometric analysis

INTRODUCTION

There are no established criteria in selecting pleural effusion (PE) specimens for flow cytometric analysis (FCA). FCA on effusion specimens may be ordered by a clinician or a cytopathologist. In an effort to improve lab test utilization, this retrospective study aims to identify characteristics of PE specimens on which the addition of FCA has high diagnostic yield.

MATERIALS AND METHODS

We identified consecutive cases of PE cytology specimens on which FCA was performed over a 5-year period (2014-2019). Patient demographic data and history, FCA diagnosis, cytologic diagnosis, cellular quantity and composition, and peripheral blood cell counts were collected. Chi-square, Mann-Whitney U, and t tests were used when appropriate with a significance level of P < 0.05.

RESULTS

We identified 164 FCA cases corresponding to 142 patients (age: 19-90 years; male:female 2:1). The majority of cases had no abnormality by cytologic examination, whereas others were obviously malignant due to non-hematologic malignancy. Most (119 of 164, 73%) had negative immunophenotypic studies by FCA. Forty-five of 164 (27%) FCA cases were positive for a monoclonal myeloid or lymphoid population. Clinicopathologic features associated with positive FCA results included a history of hematologic malignancy, peripheral blood lymphocytes of ≥20%, the presence of a monomorphic lymphoid population, large atypical cells, and mitoses.

CONCLUSIONS

This study identifies features that are associated with positive FCA in PE cytology specimens. Using these features by cytopathologists to order FCA on PE specimens as a reflex test would significantly reduce unnecessary testing and improve FCA utilization.

Diagnostic role of cytology in serous effusions of patients with hematologic malignancies

BACKGROUND

We investigated serous effusions occurring during the course of an already known hematologic neoplasia or as a first manifestation of it. We correlated cytology results with flow cytometry results, when available. In the absence of flow cytometry, our correlation was based on clinical follow up information obtained retrospectively. We evaluated our results in relation to the data of the literature and we considered some new suggestions for the improvement of cytology service.

METHODS

Serous effusions in hematologic patients were retrieved from the files of the Department of Cytology, Laiko Hospital, for a period of 2 years. All patients had enrolled either a previous hematologic history, or a suspicious clinical and imaging status. Seventy-three serous effusions were included. Cytology reports consisting of morphology and immunocytochemistry assessment were correlated to flow cytometry results and, occasionally, to clinical follow-up.

RESULTS

In the group of patients with previous history, sensitivity was 82.76%, positive predictive value was 100%, specificity 100%, and negative predictive value was 58.33%. In the group of patients without previous history, sensitivity and positive predictive value were both 91%, whereas specificity and negative predictive value could not be estimated.

CONCLUSION

We provide evidence that the diagnostic accuracy of cytology with the adjunct of immunocytochemistry is high compared to flow cytometry for detecting hematologic malignancies. In order to improve clinical performance, it is suggested that a cytology triage of serous effusions in all patients with hematologic malignancy must be implemented.

Forty-nine cases of acute lymphoblastic leukaemia/lymphoma in pleural and pericardial effusions: A cytological-histological correlation

INTRODUCTION

Acute lymphoblastic leukaemia/lymphoma (ALL/LBL) is an aggressive entity of precursor lymphoid neoplasm and may cause malignant serous effusion (SE). The current study aimed to analyse the characteristics of SE cytology of ALL/LBL including cytomorphology, immunophenotyping, clonality and evaluate the effectiveness of SE cytology as a diagnostic method for ALL/LBL.

METHODS

SE specimens with final diagnosis of ALL/LBL from 2006 to 2016 were reviewed for clinical data, cytomorphological features and ancillary studies. Cytodiagnoses were compared with histodiagnoses, and the discordant cases were analysed.

RESULTS

A total of 49 specimens including 47 pleural fluids and 2 pericardial fluids from 49 patients were evaluated. Cytomorphology revealed lymphoblasts varied from small size with scant cytoplasm, condensed nuclear chromatin and indistinct nucleoli to large size with dispersed nuclear chromatin and multiple variably prominent nucleoli. Nuclear clefts and hand mirror-shaped blasts were demonstrated. The positive rates of CD99 and terminal deoxynucleotidyl transferase were 90.9% and 81.6%, respectively. Both monoclonal immunoglobulin (Ig)H and T-cell receptor-γ gene rearrangements were demonstrated in 1 of 3 cases. Monoclonal T-cell receptor-γ gene rearrangement was found in 10 of 11 cases. Monoclonal IgH and/or Ig? gene rearrangements were revealed in 2 of 3 cases. Cytodiagnoses included 4 ALL/LBL, 3 B-ALL/LBL and 42 T-ALL/LBL. Histodiagnoses were available in 24 cases including 2 ALL/LBL, 2 B-ALL/LBL and 20 T-ALL/LBL. The concordance rates of cytological-histological diagnoses were 66.7%, 0% and 95.2% in the three categories, respectively. There were 3 cases with discrepancies of cell lineages.

CONCLUSIONS

SE cytological evaluation is a reliable and effective method for the diagnosis of ALL/LBL.

Utility of flow cytometry analysis for pleural and peritoneal fluids

INTRODUCTION

Pleural and peritoneal/ascites fluid samples with many lymphocytes are commonly received in the cytology laboratory. It is often difficult to distinguish reactive lymphocytes from hematopoietic malignancy based on morphology alone, however. Flow cytometry can be a useful adjunct in body fluids, although literature on this subject is limited.

MATERIALS AND METHODS

This study is a single-institution 5-year retrospective review of 377 fluid samples from 341 patients with corresponding flow cytometry analysis. The cytologic findings were correlated with the flow cytometry results and clinical data, as available.

RESULTS

Of 4158 pleural fluids received over 5 years, 325 (7.8%) had corresponding flow cytometry analysis. Of these 325 samples, 57 (17.5%) were positive for hematopoietic malignancy by flow cytometry. Of the positive cases, only 24 (8.7%) represented a new diagnosis of hematopoietic malignancy (ie, did not have a known history). Of 3020 peritoneal/ascites fluids received over 5 years, 52 (2%) had corresponding flow cytometry. Of these, 8 were positive for hematopoietic malignancy, and only 2 represented a presumed new diagnosis.

CONCLUSIONS

Routine flow cytometry analysis for pleural and peritoneal/ascitic fluids is of limited utility, with only rare cases positive for hematopoietic malignancy without a known history. Of these cases, many had atypical cells that suggested a positive diagnosis. Conversely, in cases with a known history, about 75% were positive for hematopoietic malignancy. Our study suggests that the utility of flow cytometry for pleural and peritoneal/ascitic fluids is limited, and should be used sparingly in cases without atypical cytologic features, high clinical suspicion, or known history.

Follicular Lymphoma Diagnosed With Medical Thoracoscopy

Non-Hodgkin lymphomas may present with a recurrent pleural effusion, usually with involvement of other thoracic or extrathoracic sites. Lymphomas typically presenting with pleural disease include primary effusion lymphoma and pyothorax-associated lymphoma. We describe an unusual case of recurrent pleural effusion secondary to follicular lymphoma with no other known extrathoracic involvement at the time of diagnosis.

Flow Cytometry and Effusions in Lymphoproliferative Processes and Other Hematologic Neoplasias

Cytopathologists are regularly confronted with lymphocyte-rich effusions, and the definite decision of whether the lymphocytosis is of a purely reactive nature or a presentation of an indolent lymphoma may be an extremely difficult one based on microscopy alone. Flow cytometry (FC) offers many advantages in terms of its application in body cavity fluids, and it has proven to be very useful both in the setting of a known disease and for new lymphoma diagnoses. In this paper, the studies published in recent years dealing with the applications of FC in body cavity effusions in the context of hematologic neoplasia are reviewed, stressing the integrative diagnostic approach. The incorporation of microscopical, immunophenotypical, and molecular findings from examinations of the cellular content of effusions and the interpretation of results in relation to the current WHO classification of hematolymphoid malignancies give cytopathologists new perspectives on advanced and clinically highly relevant diagnostics.

Role of Epstein-Barr virus status and immunophenotypic studies in the evaluation of exfoliative cytology specimens from patients with post-transplant lymphoproliferative disorders

BACKGROUND

Post-transplant lymphoproliferative disorders (PTLDs) are well characterized in tissue sections, but their evaluation in exfoliative cytology specimens is limited. This study reports a 25-year experience with PTLDs in exfoliative cytology specimens.

METHODS

All solid organ or allogeneic stem cell transplant recipients with PTLDs and exfoliative cytology specimens from 1987 to 2011 were identified. The cytomorphology, Epstein-Barr virus (EBV) status, flow cytometry, immunohistochemistry, and molecular studies were reviewed from all exfoliative cytology specimens previously diagnosed as atypical lymphoid proliferations or PTLDs.

RESULTS

A total of 55 patients (age range, 1-72 years) with PTLDs had 434 exfoliative cytology specimens. Thirty-six of the 55 patients (65%) had 54 specimens with abnormal lymphoid proliferations (12% of the specimens), and 26 of these patients had 37 specimens available for review (15 cerebrospinal fluid specimens, 12 peritoneal fluid specimens, 9 pleural fluid specimens, and 1 bronchoalveolar lavage fluid specimen). Thirty percent of the reviewed cytology specimens were diagnostic of PTLDs, including 8 cases of monomorphic post-transplant lymphoproliferative disorder (M-PTLD) with abnormal B/T-cell populations identified with flow cytometry/immunohistochemistry and 3 EBV-positive specimens with a differential diagnosis of polymorphic PTLD versus M-PTLD. All cases diagnostic of a PTLD had 1 to 3 ancillary studies performed. Forty percent of the cytology specimens (15 of 37) were suspicious for a PTLD, but ancillary studies were performed for only a third of them, and they did not support a definitive diagnosis of a PTLD. Thirty percent of the cytology specimens (11 of 37) appeared reactive, but they lacked sufficient ancillary studies to exclude a PTLD.

CONCLUSIONS

Atypical lymphoid proliferations are common in exfoliative cytology specimens from patients with PTLDs, and they require ancillary studies at least including immunophenotyping and EBV evaluations for a definitive diagnosis. Cancer Cytopathol 2016;124:425-35. © 2016 American Cancer Society.

Pericardial, pleural and peritoneal involvement in a patient with primary gastric mantle cell lymphoma

Primary gastric mantle cell lymphoma is a rare form of gastointestinal tumour. Although peritoneal carcinomatosis accompanied by malignant ascites is relatively common, mantle cell lymphoma presenting with ascites is rare. Also, effusions involving pericardial and pleural cavities are uncommon during the course of lymphomas. We report the first case in which pericardial, pleural and peritoneal effusion of a primary gastric mantle cell lymphoma.

Detection of acute lymphoblastic leukemia involvement in pleural fluid in an adult patient with ataxia telangiectasia by flow cytometry method

Ataxia-telangiectasia (AT) is a rare multisystem, neurodegenerative genetic disorder. Patients should be closely monitored due to risk of malignancy development. Due to its wide clinical heterogeneity, it often leads physicians to an inaccurate or missed diagnosis, and insight into this rare disease is important. Pediatric patients may develop lymphomas and acute lymphoblastic leukemia (ALL). However, in adults, there are limited numbers of reports regarding association of AT and ALL. Rarely, ALL cases may present with pleural fluid involvement. In our study, we presented an adult case with AT, in which ALL involvement was detected in pleural fluid by flow cytometry (FC). A 20-years old male presented to emergency department with fever, shortness of breath and cough, as he had been followed with a diagnosis of AT. The following findings were detected in laboratory tests: Hb, 11.5 g/L; WBC, 36 × 10(9)/L; Plt: 140 × 10(9)/L. Blastic cells were observed in peripheral blood smear. On chest radiography, pleural fluid appearance was observed. On thorax CT, pleural fluid was detected in both hemithorax. Cytoplasmic CD3(+) and superficial CD3 (+), CD45 (+), CD5 (+), CD7 (+) and CD38 (+) was found in the flow cytometric evaluation of peripheral blood. Superficial CD3 (+), CD2 (+), CD5 (+) and CD7 (+) were found in flow cytometric evaluation of pleural fluid. These findings were considered as consistent with pleural involvement of T-ALL. FC is a potentially useful diagnostic tool for clinical practice and it is a convenience method which has an important role in detection of ALL in patients with pleural fluid.

Extraoral plasmablastic lymphoma detected using ascitic fluid cytology and flow cytometry: a case report with a review of the literature

BACKGROUND

Plasmablastic lymphoma (PL) is a relatively new category of lymphoma, which has been considered to be found predominantly in the oral cavity and has a strong association with HIV.

CASE

We report a case of extraoral/mesenteric PL detected using cytological examination of ascitic fluid assisted by flow cytometric (FC) analysis. The cells were positive for CD38, CD138, CD10, CD45 and CD56 and negative for CD3, CD19, CD20 and CD79a, with cytoplasmic lambda light-chain restriction. We also reviewed 67 cases of extraoral PL from the available literature and found them to be less often associated with HIV (than oral PL), occurring mostly in males aged 30-60 years, with the most common extraoral site being the anorectal region.

CONCLUSION

A high index of suspicion at the level of the cytopathologist is imperative for identifying lymphoma cells in a body fluid. A rare entity like PL can also be diagnosed on cytology assisted by ancillary techniques (like FC), without the need for a biopsy. We also suggest that the minimum panel to diagnose PLs should include CD138, MUM-1, Ki-67, ALK-1, CD3, immunoglobulin light-chains, CD20 and PAX5.

Detection of the GD2+/CD56+/CD45- immunophenotype by flow cytometry in cerebrospinal fluids from a patient with retinoblastoma

Triple-color flow cytometry with a panel of antibodies comprising GD2, CD56, and CD45 was performed to analyze cerebrospinal fluids (CSF) from a patient with retinoblastoma who was suspicious of meningeal metastasis based on clinical presentation. Our results showed that the cells in CSF demonstrated the immunophenotype positive for GD2 and CD56 but negative for CD45 antigen, which suggested the presence of CSF metastasis of retinoblastoma. At the end of eight cycles of intrathecal chemotherapy, CSF specimen was analyzed with Flow cytometry immunophenotyping (FCI) again and the result showed no detectable malignant cells with the same immunophenotype. Our conclusion is that FCI can be a quick and reliable method for the diagnosis of CSF metastasis of retinoblastoma and the immunophenotype (GD2+, CD56+, and CD45-) can be used to recognize residual retinoblastoma cells in CSF.

Concurrent pleural infiltration by chronic lymphocytic leukemia and adenocarcinoma of unknown primary site diagnosed by effusion cytology

Synchronous malignancies in a pleural effusion are rare. A case of concurrent pleural infiltration by adenocarcinoma of unknown primary site and chronic lymphocytic leukemia (CLL) is presented in this case study, which was diagnosed by effusion cytology. Pleural effusion is not an uncommon complication in patients with B-CLL. Even in a pleural effusion rich in monoclonal lymphocytes, the presence of a second cancer must be excluded because this can be the main cause of mortality. The role of cytology in such cases is of paramount importance.

Ascitic fluid cytology and flow cytometry in the primary diagnosis of lymphoma - a case report

Primary diagnosis of lymphomas from ascitic fluid is rare. We report a case in which a patient being worked up as a case of carcinoma head of pancreas turned out to be a lymphoma on routine ascitic fluid examination and was further sub-classified as a CD 10+ B-cell lymphoma on flow cytometric analysis.

Mediastinal mass and malignant pleural effusion in an aleukemic case with pre-B acute lymphoblastic leukemia

Pleural effusions and mediastinal masses are associated with certain types of hematologic malignancies. We report a 20-year-old man with a pleural effusion, a mediastinal mass, and a normal hemogram. The cytology of the pleural effusion initially suggested a lymphoma. However, an immunophenotypic study of the effusion revealed the following: TdT+, CD34+, CD19+, CD7(-), CD33(-), CD10(-), sIgM(-), and positive cytoplasmic mu heavy-chain immunoglobulins. After a bone marrow examination, we diagnosed the patient with pre-B acute lymphoblastic leukemia (ALL). This is the first reported case of a malignant pleural effusion and a mediastinal mass that preceded pre-B ALL. After standard therapy for ALL, the patient has been disease-free for 7 years.

2006 Bethesda International Consensus recommendations on the flow cytometric immunophenotypic analysis of hematolymphoid neoplasia: medical indications

The clinical indications for diagnostic flow cytometry studies are an evolving consensus, as the knowledge of antigenic definition of hematolymphoid malignancies and the prognostic significance of antigen expression evolves. Additionally the standard of care is not routinely communicated to practicing clinicians and diagnostic services, especially as may relate to new technologies. Accordingly there is often uncertainty on the part of clinicians, payers of medical services, diagnostic physicians and scientists as to the appropriate use of diagnostic flow cytometry. In an attempt to communicate contemporary diagnostic utility of immunophenotypic flow cytometry in the diagnosis and follow-up of patients with hematolymphoid malignancies, the Clinical Cytometry Society organized a two day meeting of international experts in this area to reach a consensus as to this diagnostic tool. This report summarizes the appropriate use of diagnostic flow cytometry as determined by unanimous approval of these experienced practitioners.

The diagnosis of malignancy in effusion cytology: a pattern recognition approach

This review presents a pattern recognition approach for the diagnosis of malignant effusions. The cytomorphologic features of reactive mesothelial proliferation, mesothelioma and metastatic carcinoma are presented. In addition, the role of ancillary studies in challenging cases and the importance of integrating clinical findings are stressed. An algorithmic approach to the workup of serous effusions as well as pitfalls for false-positive diagnosis are discussed.

Serous effusions in malignant lymphomas: A review

Serous effusions are a common complication of lymphomas. Although the frequency of pleural effusion is 20-30% in non-Hodgkin's lymphoma (NHL) and Hodgkin's disease (HD), the involvement of peritoneal and pericardial cavities is uncommon. Among lymphoma subtypes, T-cell neoplasms, especially the lymphoblastic lymphomas, more frequently involve the serous fluids. The thoracic duct obstruction and impaired lymphatic drainage appear to be the primary mechanism for pathogenesis of pleural effusion in HD and direct pleural infiltration is the predominant cause in NHL. There is wide variation in rate of positive cytologic findings of NHL in pleural effusion (22.2-94.1%). Cytologic features of specific lymphoma subtypes such as lymphoblastic lymphoma, follicular center cell lymphoma, including Burkitt-type lymphoma, marginal zone lymphoma, MALT lymphoma, and anaplastic large-cell lymphoma, etc., have been described in the literature. The differential diagnostic problems of lymphomas in serous effusions include reactive lymphocytoses, early involvement by lymphomatous process, small round-cell tumors (SRCT), and presence of look-alike of Reed-Sternberg cells. To overcome these difficulties, various ancillary studies, including immunocytochemistry (ICC), morphometry, flow cytometry (FCM), and cytogenetics/molecular genetics (PCR, in-situ hybridization, and Southern blotting), have been performed on effusion specimens. ICC not only distinguishes lymphomas from reactive lymphocytoses and SRCTs, it significantly modifies the morphologic diagnosis to achieve a better classification of lymphomas. Combined morphology and immunophenotyping by FCM, has a sensitivity as well as specificity of 100%. Morphometry also distinguishes reactive lymphocytoses from malignant lymphoma with a high degree of sensitivity (>85%) and specificity (>95%). Limitations of individual ancillary techniques can be overcome by using multiple parameters. Although lymphomas rarely present as serous effusions without the involvement of other thoracic and extrathoracic sites, a small group of lymphomas called primary effusion lymphomas (PEL) exhibit exclusive or dominant involvement of serous cavities, without a detectable solid tumor mass. This body cavity based lymphoma (BCBL) is a distinct clinicopathologic entity and is found predominantly in AIDS patients with preexisting Kaposi sarcoma. In the absence of obstructive or infiltrative tumor mass, its pathogenesis has been attributed to stimulation by vascular endothelial growth factor (VEGF)/vascular permeability factor (VPF), leading to vascular leakage. Cytomorphologically, PEL is usually a large-cell lymphoma, which appears to bridge features of large-cell immunoblastic and anaplastic large-cell lymphoma (ALCL). Most of these cases comprise a unique subgroup of B-cell lymphoma, with features of both high-grade anaplastic and B-immunoblastic lymphoma, but T-cell and/or natural killer cell immunophenotypes are described. Its association with various viral DNAs has been studied in detail by molecular techniques. Pleural effusion due to lymphomas, either primary or otherwise, is considered as one of the factors adversely influencing overall survival. The presence of pleural effusion at the time of presentation is not only associated with extremely poor outcome of lymphomas, it is also a predictor of disease relapse after chemotherapy and decreased survival. When the patients of lymphomatous pleural effusions with and without mediastinal mass present in respiratory distress, thoracocentesis is the initial diagnostic and therapeutic choice in these patients. In such situations, cytology along with ancillary studies not only gives a quick diagnosis of lymphoma, but also offers prognostically significant information such as classification of lymphomas, its grade and immunophenotype, and presence/absence of viral DNAs and tumor lysis syndrome.