The use of flow cytometry in the diagnosis and monitoring of malignant hematological disorders

Biomarker Technologies to Support Early Clinical Immuno-oncology Development: Advances and Interpretation

Today, there is a huge effort to develop cancer immunotherapeutics capable of combating cancer cells as well as the biological environment in which they can grow, adapt, and survive. For such treatments to benefit more patients, there is a great need to dissect the complex interplays between tumor cells and the host's immune system. Monitoring mechanisms of resistance to immunotherapeutics can delineate the evolution of key players capable of driving an efficacious antitumor immune response. In doing so, simultaneous and systematic interrogation of multiple biomarkers beyond single biomarker approaches needs to be undertaken. Zooming into cell-to-cell interactions using technological advancements with unprecedented cellular resolution such as single-cell spatial transcriptomics, advanced tissue histology approaches, and new molecular immune profiling tools promises to provide a unique level of molecular granularity of the tumor environment and may support better decision-making during drug development. This review will focus on how such technological tools are applied in clinical settings, to inform the underlying tumor-immune biology of patients and offer a deeper understanding of cancer immune responsiveness to immuno-oncology treatments.

Flow cytometry shows added value in diagnosing lymphoma in brain biopsies

Background

To assess the sensitivity, specificity and turnaround time of flow cytometric analysis on brain biopsies compared to histology plus immunohistochemistry analysis in tumors with clinical suspicion of lymphoma.

Methods

All brain biopsies performed between 2010 and 2015 at our institution and analyzed by both immunohistochemistry and flow cytometry were included in this retrospective study. Immunohistochemistry was considered the gold standard.

Results

In a total of 77 biopsies from 71 patients, 49 lymphomas were diagnosed by immunohistochemistry, flow cytometry results were concordant in 71 biopsies (92.2%). We found a specificity and sensitivity of flow cytometry of 100% and 87.8%, respectively. The time between the biopsy and reporting the result (turnaround time) was significantly shorter for flow cytometry, compared to immunohistochemistry (median: 1 vs. 5 days).

Conclusions

Flow cytometry has a high specificity and can confirm the diagnosis of a lymphoma significantly faster than immunohistochemistry. This allows for rapid initiation of treatment in this highly aggressive tumor. However, since its sensitivity is less than 100%, we recommend to perform histology plus immunohistochemistry in parallel to flow cytometry. © 2018 The Authors. Cytometry Part B: Clinical Cytometry published by Wiley Periodicals, Inc. on behalf of International Clinical Cytometry Society

Diagnosis of acute leukemia in cerebrospinal fluid (CSF-acute leukemia)

Cerebrospinal fluid-acute leukemia (CSF-acute leukemia) is a frequent and serious complication in patients with acute leukemia. One of the major problems of this complication is the diagnosis process itself. CSF cytology is currently considered the gold standard for establishing the diagnosis, a technique which presents various processing limitations, seriously impacting the predictive values. In the last 11 years, studies of CSF flow cytometry analysis done in patients with acute leukemia have demonstrated superiority in comparison with CSF cytology. Although comparative studies between these two techniques have been reported since 2001, no new consensus or formal changes to the gold standard have been established for the CSF acute leukemia diagnosis. The evidence suggests that positive flow cytometry cases, considered as indeterminate cases, will behave like disease in the central nervous system (CNS). Nevertheless, we think there are some variables and considerations that must be first evaluated under research protocols before CNS relapse can be established with only one positive flow cytometry analysis in the setting of indeterminate CSF samples. This paper proposes a diagnostic algorithm and complementary strategies.

Diagnostic strategies to investigate cerebrospinal fluid involvement in haematological malignancies

Central nervous system (CNS) involvement is a fatal complication of certain haematological malignancies with an incidence as high as 25% in specific leukaemia/lymphoma subtypes. It is often accompanied by 'occult' cerebrospinal fluid (CSF) involvement at diagnosis, which is frequently missed by conventional cytology examination. Unfortunately, a diagnostic gold standard is yet unavailable since CSF morphology may be negative for malignant cells in up to 45% of patients with suspected meningeal involvement. New technologies such as flow cytometry, molecular genetics and newer biomarkers may improve sensitivity and specificity facilitating the diagnosis of CNS involvement as well as effective prophylaxis and successful treatment.

Final results of a multicenter trial addressing role of CSF flow cytometric analysis in NHL patients at high risk for CNS dissemination

This prospective study compared diagnostic and prognostic value of conventional cytologic (CC) examination and flow cytometry (FCM) of baseline samples of cerebrospinal fluid (CSF) in 174 patients with newly diagnosed aggressive non-Hodgkin lymphoma (NHL). FCM detected a neoplastic population in the CSF of 18 of 174 patients (10%), CC only in 7 (4%; P < .001); 11 patients (14%) were discordant (FCM+/CC−). At a median follow-up of 46 months, there were 64 systemic progressions and 10 CNS relapses, including 2 patients with both systemic and CNS relapses. Two-year progression-free and overall survival were significantly higher in patients with FCM− CSF (62% and 72%) compared with those FCM+ CSF (39% and 50%, respectively), with a 2-year CNS relapse cumulative incidence of 3% (95% confidence interval [CI], 0-7) versus 17% (95% CI, 0-34; P = .004), respectively. The risk of CNS progression was significantly higher in FMC+/CC− versus FCM−/CC− patients (hazard ratio = 8.16, 95% CI, 1.45-46). In conclusion, FCM positivity in the CSF of patients with high-risk NHL is associated with a significantly higher CNS relapse risk and poorer outcome. The combination of IV drugs with a higher CNS bioavailability and intrathecal chemotherapy is advisable to prevent CNS relapses in FCM+ patients.

Isolated leptomeningeal infiltration of a primary CNS B-cell lymphoma diagnosed by flow cytometry and confirmed by necropsy

BACKGROUND

The diagnosis of the isolated leptomeningeal involvement of a primary central nervous system B-cell lymphoma without parenchyma lesions may be difficult. Patients with leptomeningeal meningeosis lymphomatosa can present with various neurologic deficits.

AIMS OF THE STUDY

To demonstrate the impact of cerebrospinal fluid (CSF) flow cytometry in the diagnosis of an isolated leptomeningeal manifestation of B-cell lymphoma by presenting an interesting case report.

METHODS

Flow cytometric analysis of B-cell monoclonality of the CSF was performed as complementary diagnostic procedure in addition to CSF cytology. Final diagnosis was confirmed by necropsy.

RESULTS

We suspected isolated leptomeningeal manifestation of B-cell lymphoma with palsy of the VI and VII cranial nerves in a 79-year-old male, because of mononuclear pleocytosis in CSF. Interestingly, the decisive diagnostic hint was given by implementation of flow cytometry of the CSF. Diagnosis was confirmed by postmortem autopsy.

CONCLUSION

Our case shows that flow cytometry of the CSF in addition to conventional CSF cytology has the potential to accelerate diagnosis of lymphomeningeal infiltration of B-cell lymphoma.

Polychromatic flow cytometry in the clinical laboratory

Technological advances in flow cytometry include increasingly sophisticated instruments and an expanding range of fluorochromes. These advances are making it possible to detect an increasing number of markers on a single cell. The term polychromatic flow cytometry applies to such systems that detect five or more markers simultaneously. This review provides an overview of the current and future impact of polychromatic flow cytometry in the clinical laboratory. The use of multiple markers has several advantages in the diagnosis and monitoring of haematological malignancies. Cell populations can be analysed more comprehensively and efficiently, and abnormal populations can be distinguished more readily when normal counterparts are present. Polychromatic flow cytometry is particularly useful in the evaluation of plasma cells, and the role of flow cytometry in the assessment of plasma cell disorders is reviewed in depth. There is improved sensitivity in the assessment of small populations, which is critical in the evaluation of minimal residual disease. Flow cytometry can also play a role in assessment of circulating tumour cells in carcinoma. Introduction of polychromatic flow cytometry is a complex process with many challenges including design of antibody panels and instrument compensation. Developments in data analysis are required to realise the full benefits of the other technical advances. Standardisation of protocols may reduce inter-laboratory variation. While the complexity of polychromatic flow cytometry creates challenges, it has substantial potential to improve clinical analysis.

Novel approaches to treating leptomeningeal metastases

Leptomeningeal metastasis is a devastating complication of the central nervous system in patients with late-stage solid or hematological cancers. Leptomeningeal metastasis results from the multifocal seeding of the leptomeninges by malignant cancer cells. Although central nervous system metastasis usually presents in patients with widely disseminated and progressive late-stage cancer, malignant cells may spread to the cerebrospinal fluid during earlier disease stages in particularly aggressive cancers. Treatment of leptomeningeal metastasis is largely palliative but will often provide stabilization and protection from further neurological deterioration and improve quality of life. There is a need to raise awareness of the impact of leptomeningeal metastases on cancer patients and its known and putative biological basis. Novel diagnostic approaches include identification of biomarkers that may stratify the risk for developing leptomeningeal metastasis. Current therapies can be used more effectively while waiting for advanced treatments to be developed.

Diffuse large B-cell lymphoma with involvement of the kidney: outcome and risk of central nervous system relapse

BACKGROUND

Renal involvement is uncommon in diffuse large B-cell lymphoma. Recent data suggest that it is an independent risk factor for central nervous system relapse. We reviewed the clinical features, risk of central nervous system involvement, and survival of patients with diffuse large B-cell lymphoma with involvement of the kidney at diagnosis.

DESIGN AND METHODS

All patients with diffuse large B-cell lymphoma and renal involvement diagnosed from January 1, 1982 to December 31, 2008 at the British Columbia Cancer Agency were retrospectively identified in the Lymphoid Cancer Database. Patients were included if they were 16 years old or over, had advanced stage disease [stage III/IV, or stage I/II with B symptoms or bulky mass (>10 cm)] and were treated with curative intent. Central nervous system involvement was diagnosed by cerebrospinal fluid cytology, radiology or clinically.

RESULTS

We identified 55/2656 (2%) patients with diffuse large B-cell lymphoma and renal involvement at diagnosis. The male to female ratio was 2:1. The patients' median age was 58 years. Bilateral renal involvement was present in 24 (44%) and stage IV disease in 50 (91%). The International Prognostic Index score was 3, 4 or 5 in 52 (95%), the glomerular filtration rate was less than 30 mL/min/m² in 9 (16%) and elevated lactate dehydrogenase was recorded in 46 (84%). Twenty-five (46%) patients received CHOP plus rituximab and 30 (54%) received CHOP-like regimens without rituximab. In total, 20 (36%) patients had central nervous system involvement: four at the time of diagnosis and 16 at relapse. The median time to central nervous system relapse was 5.6 months (range, 1.2 months-4.6 years), and was not affected by the addition of rituximab (P=0.547). The 5-year overall and progression-free survival rates for the whole cohort were 29% and 25%, respectively. In patients who received rituximab, there were trends towards improved 5-year overall survival (43% versus 18%, P=0.071) and progression-free survival (40% versus 13%, P=0.057).

CONCLUSIONS

There is an exceptionally high incidence of central nervous system relapse in patients with diffuse large B-cell lymphoma and kidney involvement at diagnosis. The addition of rituximab may improve overall survival in this poor-risk population, likely through improved control of systemic disease.

Cerebrospinal fluid pleocytosis: pitfalls and benefits of combined analysis using cytomorphology and flow cytometry

BACKGROUND

Cerebrospinal fluid samples with doubtful morphologic interpretation are a common problem in the workup of patients with clinical signs for leptomeningeal disease. The authors report on the combination of morphology and flow cytometry in the diagnosis of leptomeningeal disease in patients with radiological, clinical, or cytological findings suspicious for leukemia or lymphoma with spread into the cerebrospinal fluid.

METHODS

The authors defined a set of antibodies for flow cytometric analysis, which is capable of distinguishing between malignant and nonmalignant hematopoietic cells. One hundred twenty-seven cases were analyzed with both methods.

RESULTS

The additional application of flow cytometry resulted in an improvement of diagnostic reliability in 29 of 127 cases. Diagnostic sensitivity was raised from 73% (cytology) to 96% (flow cytometry), specificity from 94% to 97%, the positive predictive value from 88% to 96%, and the negative predictive value from 76% to 97%.

CONCLUSIONS

Because the appropriate selection of markers is crucial to successful analysis, the authors suggested a highly selected panel of antibodies for flow cytometry analysis of cerebrospinal fluid samples. The authors were able to demonstrate that leptomeningeal disease caused by leukemia or lymphoma can be diagnosed by flow cytometry and discriminated from reactive pleocytosis in most cases of doubtful morphology.

Particle-sizing methods: a stationary-phase-based comparison

Stationary-phase approximation is used to examine and compare the reliability and interpretability of two main methods of particle sizing. The first method, differential light scattering, regards spherical objects having different refractive indices. Theoretical expressions are obtained, enabling the derivation of optical and geometrical properties of the object from its scattering pattern. The second method, automated microscope imaging, is considered with theoretical implications for the finite aperture of the objective lens. It is shown that, besides the well known Rayleigh resolution limit, finite aperture must affect size measurement due to optical properties of the particles. Simulation and experimental results for both differential light scattering and microscope imaging of polystyrene beads are in good agreement with theory.

Flow cytometry and cell sorting

Flow cytometry and cell sorting are well-established technologies in clinical diagnostics and biomedical research. Heterogeneous mixtures of cells are placed in suspension and passed single file across one or more laser interrogation points. Light signals emitted from the particles are collected and correlated to entities such as cell morphology, surface and intracellular protein expression, gene expression, and cellular physiology. Based on user-defined parameters, individual cells can then be diverted from the fluid stream and collected into viable, homogeneous fractions at exceptionally high speeds and a purity that approaches 100%. As such, the cell sorter becomes the launching point for numerous downstream studies. Flow cytometry is a cornerstone in clinical diagnostics, and cheaper, more versatile machines are finding their way into widespread and varied uses. In addition, advances in computing and optics have led to a new generation of flow cytometers capable of processing cells at orders of magnitudes faster than their predecessors, and with staggering degrees of complexity, making the cytometer a powerful discovery tool in biotechnology. This chapter will begin with a discussion of basic principles of flow cytometry and cell sorting, including a technical description of factors that contribute to the performance of these instruments. The remaining sections will then be divided into clinical- and research-based applications of flow cytometry and cell sorting, highlighting salient studies that illustrate the versatility of this indispensable technology.

Primary pancreatic lymphomas: a cytopathologic analysis of a rare malignancy

BACKGROUND

Primary pancreatic lymphomas (PPL) are extremely rare. Clinically, PPL usually present with symptoms of carcinoma of the pancreatic head. An accurate cytopathologic diagnosis by fine-needle aspiration (FNA) is imperative because the primary treatment is nonsurgical, based on a combination of chemotherapy and radiation therapy.

METHODS

Eight cases of PPL were identified from the pathology files of The Johns Hopkins Hospital over a 14-year period (1989-2003). All cases were diagnosed on FNA performed under radiologic guidance. Needle rinses were used to perform flow cytometric (FC) analysis. No tissue studies were performed after the FNA diagnosis was made.

RESULTS

A strong male predominance (male-to-female ratio of 7:1) was noted. The patients ranged in age from 35-75 years (mean age, 55 years). The tumors varied in size from 2-14 cm, as evaluated on the radiologic scans (mean dimension of 8.0 cm). Abdominal pain was the most common presenting symptom (six patients) followed by jaundice, acute pancreatitis, small bowel obstruction, and diarrhea. The cytomorphologic features included hypercellularity with discohesive cells with round nuclei, often prominent nucleoli, mitoses, and karyorrhexis. By FC analysis, all eight cases demonstrated a monoclonal pattern of immunoglobulin light chain expression. The patients were treated with either chemotherapy alone or in conjunction with radiation therapy or stem cell transplantation.

CONCLUSIONS

PPL is an extremely rare pathologic entity. FNA coupled with FC analysis appears to be highly accurate in the diagnosis of PPL and is the sole diagnostic modality used clinically. Based on cytomorphology, the main differential diagnoses of PPL involve secondary lymphoma, pancreatic endocrine neoplasm, and florid chronic pancreatitis. An accurate FNA diagnosis of PPL is critical for timely, nonsurgical management and obviates the need for an exploratory laparotomy.

High-power blue/UV light-emitting diodes as excitation sources for sensitive detection

With advances in III-V nitride manufacturing processes, high-power light-emitting diode (LED) chips in the blue and UV wavelengths are now commercially available at reasonable cost and can be used as excitation sources in optical sensing. We describe the use of these high-power blue and UV LEDs for sensitive fluorescence detection, including chip-based flow cytometry, capillary electrophoresis (CE), and single-molecule imaging. By using a blue LED with a focusable power of approximately 40 mW as the excitation source for fluorescent beads, we demonstrate a simple chip-based bead sorter capable of enriching the concentration of green fluorescent beads from 63% to 95%. In CE experiments, we show that a mixture of analyte solution containing 30 nM 6-carboxyrhodamine 6G and 10 nM fluorescein can be separated and detected with excellent signal-to-noise ratio (approximately 17 for 10 nM fluorescein) using the collimated emission from a blue LED; the estimated mass detection limit was approximately 200 zmol for fluorescein. We also demonstrated ultrasensitive fluorescence imaging of single rhodamine 123 molecules and individual lambda-DNA molecules. At a small fraction of the cost of an Ar+ laser, high-power blue and UV LEDs are effective alternatives for lasers and arc lamps in fluorescence applications that demand portability, low cost, and convenience.

High incidence of occult leptomeningeal disease detected by flow cytometry in newly diagnosed aggressive B-cell lymphomas at risk for central nervous system involvement: the role of flow cytometry versus cytology

We assessed the cerebrospinal fluid (CSF) by flow cytometry and cytology in 51 newly diagnosed and 9 treated aggressive B-cell lymphomas at risk for central nervous system (CNS) involvement to examine the utility of flow cytometry, incidence of CSF disease, and clinical surrogates of CNS spread. Multicolor flow cytometry using multiple antibody panels for light chains and B- and T-cell antigens identified neoplastic clones that constituted as little as 0.2% of total CSF lymphocytes. Among 51 newly diagnosed patients, 11 (22%) had occult CSF involvement. All 11 were detected by flow cytometry but only 1 by cytology (P = .002). Among 9 treated patients, CSF involvement was detected by flow cytometry alone in 2 and also by cytology in 1 case. CSF chemistry and cell counts were similar in patients with and without CSF lymphoma. Only the number of extranodal sites was associated with occult CSF lymphoma in newly diagnosed patients by univariate (P = .006) or logistic regression analysis (P = .012). We hypothesize that the biologic phenotype associated with colonization of extranodal sites leads to CNS spread, possibly related to the microenvironment. Patients at risk for CNS spread should undergo staging CSF evaluation by flow cytometry.

CD56 expression of neuroendocrine neoplasms on immunophenotyping by flow cytometry: a novel diagnostic approach to fine-needle aspiration biopsy

BACKGROUND

CD56 antigen or NCAM (neural cell adhesion molecule) has an established role in the diagnosis of non-Hodgkin lymphoma (NHL)-natural killer cell type and other hematologic malignancies. Therefore, it is included routinely in the panel of antibodies for flow cytometric (FC) analysis of suspected lymphomatous tissue specimens obtained from fine-needle aspiration biopsy (FNAB). The authors evaluated the role of CD56 expression on FC of neuroendocrine (NE) tumors. An initial diagnosis of NHL was suspected based on an on-site FNAB evaluation.

METHODS

Ten FNABs were identified from the cytopathology files at The Johns Hopkins Hospital, Baltimore, MD (2000-2001). Flow cytometric analysis was negative for NHL but revealed a CD56-positive nonlymphoid cell population. An FNAB evaluation was performed on air-dried Diff-Quik-stained smears and FC analysis used a fixed panel of 12 antibodies (B-cell markers, T-cell markers, CD33, CD56, and CD71). Immunoperoxidase staining (IPOX) was performed on the cell block sections from four of the tissue specimens using epithelial and NE markers, CD56, desmin, and O13 antibodies. Sites of FNAB included the lung (five cases), liver (one case), lymph node (three cases), and peritoneum (one case). Only one patient had a history of cancer at the time of FNAB.

RESULTS

All cytologic diagnoses were confirmed by histopathologic follow-up on resection or biopsy or both. Diagnoses included small cell carcinoma (eight cases), Merkel cell carcinoma (one case), and primitive neuroectodermal tumor/Ewing sarcoma (one case). All tissue specimens that underwent IPOX stained strongly with NE markers, with one tissue section staining only with O13.

CONCLUSIONS

CD56 expression by FC in the presence of negative immunostaining with lymphoid markers represented a unique yet highly specific method for the diagnosis of NE tumors by FNAB. This procedure eliminated the need for further IPOX studies on the already limited cytologic sample and provided a timely and accurate diagnosis.

High-speed cell sorting: fundamentals and recent advances

Cell sorters have undergone dramatic technological improvements in recent years. Driven by the increased ability to differentiate between cell types, modern advances have yielded a new generation of cytometers, known as high-speed cell sorters. These instruments are capable of higher throughput than traditional sorters and can distinguish subtler differences between particles by measuring and processing more optical parameters in parallel. These advances have expanded their use to facilitate genomic and proteomic discovery, and as vehicles for many emerging cell-based therapies. High-speed cell sorting is becoming established as an essential research tool across a broad range of scientific fields and is poised to play a pivotal role in the latest therapeutic modalities.

A standardized flow cytometric method for screening paroxysmal nocturnal haemoglobinuria (PNH) measuring CD55 and CD59 expression on erythrocytes and granulocytes

PNH is a disorder of the pluripotent stem cells resulting in a deficient expression of membrane-bound GPI-anchored proteins in different cell types. Several flow cytometric approaches are designed to detect this antigen deficiency. But they all require drawing and testing of normal samples as control. Therefore, in the present study two flow cytometric assays for the detection of CD55 and CD59 deficiency in erythrocytes (REDQUANT CD55/CD59) and granulocytes (CELLQUANT CD55/CD59) are proposed. Precalibrated beads are used to define the cut off between normal and deficient cell populations. The specificity of the tests has been evaluated in healthy blood donors (n=52) resulting in a clear and reproducible cut off (3%) for the normal percentage of GPI-deficient cells. This cut off has been confirmed in leukaemia and lymphoma patients not suspected for developing PNH. The sensitivity has been tested in patients suffering from known PNH (n=23). Both tests performed in combination allowed a reliable detection of PNH in all patients showing antigen deficiencies in both cell types in most patients (20/23). In contrast, the PNH clones in the investigated patients with MDS (4/19) or AA (4/22) were present in granulocytes or erythrocytes, only. This underlines the necessity of analysing erythrocytes as well as granulocytes. Preliminary data regarding a possible correlation between disease activity and percentage of antigen-deficient cells lead to the assumption that haemolytic crises can only be determined on granulocytes whereas deficient erythrocytes disappeared due to complement-mediated lysis of the PNH clone. In conclusion, the combination of the test kits enables the differential diagnosis of PNH clones in a standardized, simple and rapid approach which may have therapeutic consequences.