The unnecessary use of short tandem repeat testing on bone marrow samples in patients after 1 year following allogeneic hematopoietic stem cell transplant.

OBJECTIVES: To determine whether the information provided by short tandem repeat (STR) testing and bone marrow (BM) biopsy specimens following hematopoietic stem cell transplant (HSCT) provides redundant information, leading to test overutilization, without additional clinical benefit. METHODS: Cases with synchronous STR and flow cytometric immunophenotyping (FCI) testing, as part of the BM evaluation, were assessed for STR/FCI concordance. RESULTS: Of 1199 cases (410 patients), we found the overall concordance between STR and FCI was 93%, with most cases (1063) classified as STR-/FCI-. Of all discordant cases, 75 (6%) were STR+/FCI-, with only 5 (6.7%) cases best explained as identification of disease relapse. Eight cases were STR-/FCI+, representing relapsed/residual disease. Analysis of cases 1 year or more from transplant (54% of all cases) indicated only 9 (1.5%) were STR+/FCI-, and none uniquely identified relapse. CONCLUSIONS: These data suggest that STR analysis performed 1 year or more post-HSCT does not identify unknown cases of relapse. Furthermore, while STR testing is critical for identifying graft failure/rejection within the first year posttransplant, FCI appears superior to STR at detecting late relapses with low-level disease. Therefore, STR testing from patients 1 year or more post-HSCT may be unnecessary, as BM biopsy evaluation is sufficient to identify disease relapse.

Therapy related AML in a case of chronic lymphocytic leukemia.

In comparison to the general population, patients with chronic lymphocytic leukemia (CLL) are at a higher risk of developing secondary malignancies. Several factors may contribute to pathogenesis, including direct effects of chemotherapy and radiation as well as the reduction of immune surveillance. Factors influencing the increased risk include the increasing age of CLL patients, chronic antigenic stimulation, and immune impairment related to CLL or chemotherapy. Compared to patients with acute myeloid leukemia (AML) that developed from de novo, therapy-related AML (t-AML) has had a poorer outcome. The range of cytogenetic abnormalities in therapy-related AML is comparable to that in de novo AML, although these patients have a significantly higher frequency of unfavourable cytogenetics, such as a complex karyotype or a deletion or loss of chromosomes 5 and/or 7. Herein, we describe a case of therapy-related AML with monocytic differentiation and t(8;16) with a residual CLL population. The aim of the present case is to highlight rare occurrence of therapy related AML with t(8;16) in CLL after fluderabine based chemotherapy (FCR: fludarabine, cyclophosphamide, and rituximab). This case also highlights flowcytometric immunophenotyping as an ideal tool to characterize secondary AML along with the identification of minimal residual disease of CLL clone, which could have ignored at t-AML diagnosis. The pathogenesis of myeloid and lymphoid malignancies as well as their co-existence can be studied by focusing on such patients. Factors predisposing to the development of t-AML should be studied further, which would help in monitoring these patients more carefully.

CD34 negative HLA-DR negative acute myeloid leukaemia: A higher association with NPM1 and FLT3-ITD mutations.

INTRODUCTION: CD34 and HLA-DR negativity is often used as a characteristic immunophenotypic feature of acute promyelocytic leukaemia (APL) that differentiates APL from other subtypes of acute myeloid leukaemia (AML). However, other subtypes of AML, without expression of CD34 and HLA-DR antigens, have also been reported. METHODS: We analysed the HLA-DR negative de novo non-APL AML cases by dividing HLA-DR negative non-APL group into 2 sub-groups based on CD34 expression and compared the characteristics of CD34 negative HLA-DR negative with CD34 positive HLA-DR negative non-APL AML cases with respect to morphologic, immunophenotypic, molecular and clinical parameters. RESULTS: There were 70 cases (8.54%) which were CD34 negative HLA-DR negative and 52 cases (6.34%) were CD34 positive HLA-DR negative. The median age at diagnosis was higher in CD34 negative HLA-DR negative AML than in CD34 positive HLA-DR negative AML group (38 years vs. 12 years, p < 0.001). DIC rate was higher in CD34 negative HLA-DR negative group than the other group (p < 0.001). Median total leucocyte count was higher with higher blast count in peripheral blood and bone marrow in CD34 negative HLA-DR negative AML cases than the other group (p < 0.05). CD34 negative HLA-DR negative AML was more associated with normal karyotype (96.2% vs. 38.5%; p < 0.001), NPM1 mutation (67.8% vs. 8.3%; p < 0.001) and FLT-ITD mutation (37.3% vs. 13.9%; p < 0.05). In CD34 negative HLA-DR negative group, 16 cases had co-occurrence of NPM1 and FLT3-ITD mutations, whereas no case of CD34 positive HLA-DR negative group had such dual mutation positivity. There was poor median overall survival [3.8 months (95%CI: 2.3-7.8 months) vs. 20.4 months (95% CI: 12.8-25.7 months); p = 0.0148] in CD34 positive HLA-DR negative AML than CD34 negative HLA-DR negative AML cases. CONCLUSION: We found that the CD34 negative HLADR negative non APL AML is highly associated with NPM1 and FLT3-ITD mutation, older age at diagnosis, DIC, higher total leucocyte count, higher blast counts and normal karyotype in comparison to CD34 positive HLA-DR negative AML group. Co-occurrence of NPM1 and FLT3-ITD mutation was also exclusively seen in CD34 negative HLA-DR negative group. There was poor overall survival in CD34 positive HLA-DR negative AML than CD34 negative HLA-DR negative AML cases.

Clinico-Hematological Profile of Acute Myeloid Leukemia: Experience From a Tertiary Care Cancer Center in North India.

INTRODUCTION: Complete diagnosis of acute myeloid leukemia (AML) requires knowledge of clinical information combined with morphologic evaluation, immunophenotyping, karyotyping, and molecular genetic testing. The study intends to evaluate the demographic profile, clinical workup, and investigation, including flow cytometric immunophenotyping, in adult and pediatric age groups of AML. MATERIALS AND METHODS: This is a retrospective study of AML patients treated between January 2017 and December 2021. Clinical and demographic characteristics and investigation findings were recorded from case files and the hematology database. RESULT: A total of 896 cases of AML were registered during the given period, of which 819 cases were de-novo AML. Among those 819 cases, more than two-thirds of cases, i.e., 78.9% (N = 646), received induction chemotherapy. A significantly higher male-to-female ratio was observed (1.5:1). The median age was 22 years. The median time for diagnosis was three days and the median time for treatment intervention was four days. There were significant differences in the Eastern Cooperative Oncology Group (ECOG) performance status scores between pediatric and adult AML patients. Pediatric AML patients presented with better ECOG performance scores (ECOG performance scores 0 and 1) than adult patients (74.76% vs. 43.14%, p < 0.001). Further comparing adult vs. pediatric AML patients, normal karyotype (60.56% vs. 31.93%, p < 0.001) and NPM1 (22.25% vs. 6.72%, p < 0.001) and FLT3-ITD mutations (20.28% vs. 7.98%, p<0.001) were more common in the adult group, whereas AML-ETO (40.76% vs. 16.34%, p < 0.001) was more common in the pediatric group. CONCLUSION: The study highlights the presenting age is lower than global figures. The median time for initial diagnosis and the start of treatment is within the acceptable norms. Normal karyotype and NPM1 and FLT3 mutations were common in adult AML patients, whereas AML-ETO was more common in the pediatric cohort. These findings will help plan prospective studies and see the correlation with treatment outcomes. The laboratory workup practice currently complies with the standard guidelines at our center.

Effect of the sequence of pull of bone marrow aspirates on plasma cell quantification in plasma cell proliferative disorders.

INTRODUCTION: The evaluation of plasma cell (PC) compartment is influenced by the quality of bone marrow aspirate (BMA). Herein, we evaluated the impact of sequence of pull on quality of clinical assessment in plasma cell proliferative disorders (PCPDs). METHODS: Histomorphology along with smears from first pull and second pull BMA and flow cytometric immunophenotyping (FCMI) data from second pull aspirate were evaluated for cellularity and PC%. RESULTS: Of the 484 samples, BMA smears were adequate in 87.4% of first pull (median PC = 7%; IQR = 2-25%) and 51.2% of second pull samples (median PC = 2%; IQR = 0.5-12%; p < 0.001). Recovery of PC was least on FCMI (median PC = 0.59%; IQR = 0.14-3.07%), however, sample adequacy was met in 42.6% of samples with acquisition of ≥3 million events. Second pull smears under-reported PC% in 34% of newly diagnosed multiple myeloma (NDMM) (<10% PC) and 46% of MM on therapy (<5% PC), resulting in suboptimal assessment. Bone marrow biopsy (BMBx) was evaluated in a total of 309 cases (median PC = 10.0%; IQR 4.0-40.0%) with significantly higher numbers of BMPC% on BMBx compared with first pull smears (Mean ± 2SD: 25.9% ± 30.54 vs. 20.77% ± 20.20; p = 0.001). CONCLUSION: First pull BMA smears were of superior quality but inadequate in one-tenth of samples. Second pull smears underreported PC% and recovery of PC compartment was poorest on FCMI. Concurrent bone marrow biopsy and use of the first pull sample for FCMI along with acquisition of a higher number of cells on FCMI may enhance the quality of assessment in PCPDs.

Does minimal central nervous system involvement in childhood acute lymphoblastic leukemia increase the risk for central nervous system toxicity?

Central nervous system (CNS) involvement in childhood acute lymphoblastic leukemia (ALL) implicates enhanced intrathecal chemotherapy, which is related to CNS toxicity. Whether CNS involvement alone contributes to CNS toxicity remains unclear. We studied the occurrence of all CNS toxicities, seizures, and posterior reversible encephalopathy syndrome (PRES) in children with ALL without enhanced intrathecal chemotherapy with CNS involvement (n = 64) or without CNS involvement (n = 256) by flow cytometry. CNS involvement increased the risk for all CNS toxicities, seizures, and PRES in univariate analysis and, after adjusting for induction therapy, for seizures (hazard ratio [HR] = 3.33; 95% confidence interval [CI]: 1.26-8.82; p = 0.016) and PRES (HR = 4.85; 95% CI: 1.71-13.75; p = 0.003).

Identification and validation of suitable housekeeping genes for gene expression studies in BCR-ABL1 positive B-lineage acute lymphoblastic leukemia.

BACKGROUND: The stability of the housekeeping gene (HKG) expression is an absolute prerequisite for accurate normalization of target gene expression in a quantitative real-time polymerase chain reaction (RQ-PCR). In RQ-PCR, the widely used normalization approach involves the standardization of target genes to the most stable HKG control genes. According to the recent literature, in different experimental conditions the HKGs exhibit either up or down-regulation and thus affecting the gene expression profiles of target genes which leads to erroneous results. This implies that it is very important to select the appropriate HKG and verify the expression stability of the HKG before quantification of the target gene. METHODS AND RESULTS: The present study aims to analyze six different HKGs for their expression profiles and stability in BCR-ABL1 negative cases and validate them in BCR-ABL1 positive cases, detected by multiplex reverse transcribed polymerase chain reaction (RT-PCR). Six commonly used reference genes (GAPDH, ABL1, RNA18S, ACTB, GUSB, and EEF2) were selected in this study. RQ-PCR was performed on 24 BCR-ABL1 negative cases and the outcomes were validated on 24 BCR-ABL1 positive cases. RefFinder™, a web-based composite software was used to check the stability of HKG genes by different algorithms and comprehensive ranking of each HKG gene in BCR-ABL1 negative cases and finally validated in BCR-ABL1 positive cases. CONCLUSIONS: It was found that RNA18S, ABL1 and GUSB are good stable HKG genes, which showed minimum variability in gene expression compared to GAPDH, EEF2, and ACTB, the most commonly used HKG.

Comparison of clinical and laboratory characteristics of nonsecretory multiple myeloma and secretory multiple myeloma in a tertiary care hospital.

INTRODUCTION: Nonsecretory multiple myeloma (NSM) is a rare variant of multiple myeloma, accounting for approximately 1%-5% of all reported cases. We compared the characteristics of NSM and secretory multiple myeloma (SM). METHODS: We examined clinical and laboratory characteristics of 17 patients diagnosed with NSM and 40 patients diagnosed with SM. NSM was diagnosed based on findings of bone marrow (BM) examination, serum-free light chain (sFLC) assay, flow cytometric (FCM) immunophenotyping, chromosomal analysis, and imaging studies. RESULTS: No patient with NSM had hypercalcemia or renal insufficiency at diagnosis. Patients with NSM were less anemic (p < .05) but had higher lactate dehydrogenase levels (p < .05) than patients with SM. In addition, patients with NSM had a lower percentage of plasma cells in the BM, confirmed by manual differential count (p < .05) and FCM immunophenotyping (p < .05). The sFLC ratio in patients with NSM was abnormal (15/17, 88.2%) and was lower than that in patients with SM (p < .05). Risk stratification in Revised International Staging System revealed a low-risk tendency in patients with NSM (p = .235). CONCLUSION: NSM patients showed different clinical and laboratory characteristics from SM patients. FCM immunophenotyping and sFLC assay particularly had differences between NSM patients and SM patients. Thus, they are essential for diagnosing NSM.

Extra-nasal NK/T-cell lymphoma: A rare case with a rarer presentation.

Extra-nodal (NK/T) cell lymphoma (NKTCL) of nasal type (ENKL) presents with extranodal involvement and is associated with EBV. They are localized primarily to nasal and upper airway region but can rarely involve skin, testis, intestine, muscle, or present as a disseminated disease. We present a case of a 65-year-old male presented with bilateral orbital swelling, right parotid swelling, fever, mediastinal nodes, pleural effusion and hepatomegaly. Cytology of pleural fluid showed monomorphic lymphoid cells with folded nuclei, vesicular chromatin, inconspicuous nucleoli and granular cytoplasm. Few histiocytes showing hemophagocytosis were also noted in a background of inflammatory cells. Flow cytometric immunophenotyping of pleural fluid showed abnormal lymphoid cells which were positive for CD45, CD2 and CD56. Histopathological examination of the right eye swelling showed many atypical lymphoid cells which were positive for CD56 and negative for B and T cell markers. Based on morphological and immunophenotypic features a diagnosis of NKTCL, extra-nasal type was suggested. Patient succumbed to the disease despite aggressive therapy.

PHi-RACE: PGIMER in-house rapid & cost effective classifier for the detection of BCR-ABL1-like acute lymphoblastic leukaemia in Indian patients.

For the detection of BCR-ABL1-like ALL cases, two methodologies, specifically Gene expression profiling (GEP) or Next-generation targeted sequencing (NGS) and TaqMan based low-density (TLDA) card, are being used. NGS is very costly and TLDA is not widely commercially available. In this study, we quantified the expression of 8 selected overexpressed genes in 536 B-ALL cases. We identified 26.67% (143/536) BCR-ABL1-like ALLs using hierarchical clustering and principal component analysis. BCR-ABL1-like ALL cases were significantly older at presentation (p = 0.036) and had male preponderance (p = 0.047) compared to BCR-ABL1-negative ALL cases. MRD-positivity and induction failure were more commonest in BCR-ABL1-like ALL cases (30.55 vs.19.35% in BCR-ABL1-negative ALL cases). Lastly, we built a PHi-RACE classifier (sensitivity = 95.2%, specificity= 83.7%, AUC= 0.927) using logistic regression to detect BCR-ABL1-like ALL cases promptly at diagnosis. This classifier is beneficial for hematologists in quick decision making at baseline to start tailored treatment regimes.

Flow cytometric immunophenotyping in a liquid-based cytology sample of pleural fluid: Connecting the dots.

Primary mediastinal large B-cell lymphoma (PMBCL) is an uncommon non-Hodgkin lymphoma that is rarely described in cytology samples. The present study highlights the importance of flowcytometric immunophenotyping and immunocytochemistry in an effusion sample of an uncommon case of PMBCL.

Immunophenotypic challenges in diagnosis of CD79a negativity in a patient with B acute lymphoblastic leukemia harboring intrachromosomal amplification of chromosome 21: a case report.

BACKGROUND: Being expressed in all stages of B-cell development and having a significant value on the European Group for the Immunological Characterization of Acute Leukemias scoring system, CD79a is considered as an excellent pan-marker for lineage assignment of B cells by flow cytometry. Therefore, any lack or decrease in CD79a expression makes the diagnosis of B acute lymphoblastic leukemia cases very challenging, especially in developing country laboratories where flow cytometry analyses are not always available and, when they are, they are limited in the number of markers used for lineage assignment. Since this case is potentially interesting, we report a B acute lymphoblastic leukemia case with a lack of expression CD79a associated with intrachromosomal amplification of chromosome 21 genetic abnormality. We further discuss the practical challenges in the diagnosis of this case. CASE PRESENTATION: We present the case of an 8-year-old Caucasian boy from eastern Morocco who was initially hospitalized for a hemorrhagic syndrome. Peripheral blood smear examination showed a significant number of blasts suggesting acute leukemia. Bone marrow was studied for morphology, cytochemistry, immunophenotyping, and cytogenetics. Flow cytometry analyses showed expression of CD19, CD22, CD10, CD34, and HLA-DR markers by leukemic blasts. The expression of CD79a, which was checked with two different monoclonal antibodies, confirms that this marker was severely decreased in this case. Cytogenetic study performed by fluorescence in situ hybridization revealed the presence of intrachromosomal amplification of chromosome 21, a cytogenetic abnormality that is specific for B acute lymphoblastic leukemia. CONCLUSION: CD79a is one of the critical markers in the assignment of B acute lymphoblastic leukemia. In our case, we were lucky enough to be assisted by a few other markers of the B lineage that were positive in this case. Also, we mention the importance of proceeding to cytogenetic study, which in our case helped us to confirm the diagnosis made by flow cytometry by highlighting a cytogenetic abnormality that is specific to B acute lymphoblastic leukemia.

Negative Clinical Evolution in COVID-19 Patients Is Frequently Accompanied With an Increased Proportion of Undifferentiated Th Cells and a Strong Underrepresentation of the Th1 Subset.

The severity of SARS-CoV-2 infection has been related to uncontrolled inflammatory innate responses and impaired adaptive immune responses mostly due to exhausted T lymphocytes and lymphopenia. In this work we have characterized the nature of the lymphopenia and demonstrate a set of factors that hinder the effective control of virus infection and the activation and arming of effector cytotoxic T CD8 cells and showing signatures defining a high-risk population. We performed immune profiling of the T helper (Th) CD4+ and T CD8+ cell compartments in peripheral blood of 144 COVID-19 patients using multiparametric flow cytometry analysis. On the one hand, there was a consistent lymphopenia with an overrepresentation of non-functional T cells, with an increased percentage of naive Th cells (CD45RA+, CXCR3-, CCR4-, CCR6-, CCR10-) and persistently low frequency of markers associated with Th1, Th17, and Th1/Th17 memory-effector T cells compared to healthy donors. On the other hand, the most profound alteration affected the Th1 subset, which may explain the poor T cells responses and the persistent blood virus load. Finally, the decrease in Th1 cells may also explain the low frequency of CD4+ and CD8+ T cells that express the HLA-DR and CD38 activation markers observed in numerous patients who showed minimal or no lymphocyte activation response. We also identified the percentage of HLA-DR+CD4+ T cells, PD-1+CD+4/CD8+ T cells in blood, and the neutrophil/lymphocyte ratio as useful factors for predicting critical illness and fatal outcome in patients with confirmed COVID-19.

EuroFlow Standardized Approach to Diagnostic Immunopheneotyping of Severe PID in Newborns and Young Children.

The EuroFlow PID consortium developed a set of flow cytometry tests for evaluation of patients with suspicion of primary immunodeficiency (PID). In this technical report we evaluate the performance of the SCID-RTE tube that explores the presence of recent thymic emigrants (RTE) together with T-cell activation status and maturation stages and discuss its applicability in the context of the broader EuroFlow PID flow cytometry testing algorithm for diagnostic orientation of PID of the lymphoid system. We have analyzed peripheral blood cells of 26 patients diagnosed between birth and 2 years of age with a genetically defined primary immunodeficiency disorder: 15 severe combined immunodeficiency (SCID) patients had disease-causing mutations in RAG1 or RAG2 (n = 4, two of them presented with Omenn syndrome), IL2RG (n = 4, one of them with confirmed maternal engraftment), NHEJ1 (n = 1), CD3E (n = 1), ADA (n = 1), JAK3 (n = 3, two of them with maternal engraftment) and DCLRE1C (n = 1) and 11 other PID patients had diverse molecular defects [ZAP70 (n = 1), WAS (n = 2), PNP (n = 1), FOXP3 (n = 1), del22q11.2 (DiGeorge n = 4), CDC42 (n = 1) and FAS (n = 1)]. In addition, 44 healthy controls in the same age group were analyzed using the SCID-RTE tube in four EuroFlow laboratories using a standardized 8-color approach. RTE were defined as CD62L+CD45RO-HLA-DR-CD31+ and the activation status was assessed by the expression of HLA-DR+. Naïve CD8+ T-lymphocytes and naïve CD4+ T-lymphocytes were defined as CD62L+CD45RO-HLA-DR-. With the SCID-RTE tube, we identified patients with PID by low levels or absence of RTE in comparison to controls as well as low levels of naïve CD4+ and naïve CD8+ lymphocytes. These parameters yielded 100% sensitivity for SCID. All SCID patients had absence of RTE, including the patients with confirmed maternal engraftment or oligoclonally expanded T-cells characteristic for Omenn syndrome. Another dominant finding was the increased numbers of activated CD4+HLA-DR+ and CD8+HLA-DR+ lymphocytes. Therefore, the EuroFlow SCID-RTE tube together with the previously published PIDOT tube form a sensitive and complete cytometric diagnostic test suitable for patients suspected of severe PID (SCID or CID) as well as for children identified via newborn screening programs for SCID with low or absent T-cell receptor excision circles (TRECs).

VS38 Identifies Myeloma Cells With Dim CD38 Expression and Plasma Cells Following Daratumumab Therapy, Which Interferes With CD38 Detection for 4 to 6 Months.

OBJECTIVES: We report our institutional experience using VS38 to evaluate plasma cells by flow cytometry. METHODS: Flow cytometry data were reanalyzed to compare plasma cell percentages between the standard panel and VS38 panel. Natural killer (NK) and plasma cell CD38 median fluorescence intensity (MFI) values were calculated. RESULTS: Our cohort included 63 specimens from 38 patients. Twenty-six had received daratumumab (monoclonal anti-CD38 therapy) between less than 1 month and 17 months prior. For NK and plasma cells, CD38 MFI values were suppressed for 0 to 4 months and started to increase 4 to 6 months after last exposure. There was no significant difference in clonal plasma cell percentage calculated by the VS38 and standard panels; however, identification and quantification using the VS38 panel were easier. CONCLUSIONS: VS38 is a viable alternative to bright CD38 to identify plasma cells and particularly helpful in myeloma cases with dim CD38 and after daratumumab. Daratumumab interference with CD38 identification persists 4 to 6 months after the last exposure.

Phenotypical T Cell Differentiation Analysis: A Diagnostic and Predictive Tool in the Study of Primary Immunodeficiencies.

Multiparametric flow cytometry (MFC) represents a rapid, highly reproducible, and sensitive diagnostic technology for primary immunodeficiencies (PIDs), which are characterized by a wide range of T cell perturbations and a broad clinical and genetic heterogeneity. MFC data from CD4+ and CD8+ T cell subsets were examined in 100 patients referred for Primary Immunodeficiencies to our center. Naïve, central memory, effector memory, and terminal effector memory cell differentiation stages were defined by the combined expression CD45RA/CD27 for CD4 and CD45RA/CCR7 for CD8. Principal component analysis (PCA), a non-hypothesis driven statistical analysis, was applied to analyze MFC data in order to distinguish the diverse PIDs. Among severe lymphopenic patients, those affected by severe combined and combined immunodeficiency (SCID and CID) segregated in a specific area, reflecting a homogenous, and a more severe T cell impairment, compared to other lymphopenic PID, such as thymectomized and partial DiGeorge syndrome patients. PID patients with predominantly antibody defects were distributed in a heterogeneous pattern, but unexpectedly PCA was able to cluster some patients' resembling CID, hence warning for additional and more extensive diagnostic tests and a diverse clinical management. In conclusion, PCA applied to T cell MFC data might help the physician to estimate the severity of specific PID and to diversify the clinical and diagnostic approach of the patients.

The EuroFlow PID Orientation Tube for Flow Cytometric Diagnostic Screening of Primary Immunodeficiencies of the Lymphoid System.

In the rapidly evolving field of primary immunodeficiencies (PID), the EuroFlow consortium decided to develop a PID orientation and screening tube that facilitates fast, standardized, and validated immunophenotypic diagnosis of lymphoid PID, and allows full exchange of data between centers. Our aim was to develop a tool that would be universal for all lymphoid PIDs and offer high sensitivity to identify a lymphoid PID (without a need for specificity to diagnose particular PID) and to guide and prioritize further diagnostic modalities and clinical management. The tube composition has been defined in a stepwise manner through several cycles of design-testing-evaluation-redesign in a multicenter setting. Equally important appeared to be the standardized pre-analytical procedures (sample preparation and instrument setup), analytical procedures (immunostaining and data acquisition), the software analysis (a multidimensional view based on a reference database in Infinicyt software), and data interpretation. This standardized EuroFlow concept has been tested on 250 healthy controls and 99 PID patients with defined genetic defects. In addition, an application of new EuroFlow software tools with multidimensional pattern recognition was designed with inclusion of maturation pathways in multidimensional patterns (APS plots). The major advantage of the EuroFlow approach is that data can be fully exchanged between different laboratories in any country of the world, which is especially of interest for the PID field, with generally low numbers of cases per center.

The triple-negative (CD34-/HLA-DR-/CD11b-) profile rapidly and specifically identifies an acute promyelocytic leukemia.

INTRODUCTION: The genetic testing to confirm or rule out an acute promyelocytic leukemia (APL) typically takes a minimum of 24-72 hours. Flow cytometric immunophenotyping (FCI) on the other hand provides rapid and objective information to differentiate APL from non-APL. METHODS: FCI features, with single-tube 8-color combination using CD45, CD34, HAL-DR, CD11b, CD13, CD33, and CD117 and CD64, were compared for the 30 consecutive APL and 30 non-APL acute myeloid leukemia (AML) cases which morphologically mimicked an APL. The diagnosis was confirmed by cytogenetic or molecular genetic testing in the form of t (15:17) (q22; q21)/variant translocations or PML-RARA fusion transcript analysis. RESULTS: The APL cells lacked CD34, HLA-DR, and CD11b in 90%, 90%, and 93.3% cases, respectively. Myeloid antigens such as CD33, CD13, CD117, and CD64 were expressed in 96.7%, 96.7%, 76.7%, and 70% cases, respectively. The dual negative profiles, CD34-/HLA-DR- or HLA-DR-/CD11b-, were noted in 90% and 93.3% cases. The triple-negative (CD34-/HLA-DR-/CD11b-) profile was noted in 90% of the cases. The sensitivity, specificity, and positive predictive value (PPV) of CD34-/HLA-DR- and HLA-DR-/CD11b- profiles for the diagnosis of APL were found to be 90%, 80% & 81.1% and 93.3%, 86.7%& 87.5%, respectively. Combining the above two profiles resulted in a triple-negative profile (CD34-, HLA-DR- and CD11b-), which had a better specificity (93.3%) and positive predictive value (93.1%), with similar sensitivity. CONCLUSION: FCI is a rapid and reliable modality for the diagnosis of an APL. The triple-negative profile (CD34-/HLA-DR-/CD11b-) rapidly and specifically identifies an APL case.

A Rare Extramedullary and Extralymphoid Presentation of Mixed Phenotypic Blastic Hematolymphoid Neoplasm: A Study of Two Cases.

Mixed phenotype acute leukemia (MPAL) is a rare hematolymphoid neoplasm, representing only 3%-5% of acute leukemia. Although MPAL has been sufficiently described in the literature, its extramedullary presentation as a solitary lesion without leukemic (bone marrow [BM]) involvement is rarely described. We are presenting two cases of mixed phenotypic blastic hematolymphoid neoplasms without leukemic involvement at disease presentation in 8-year-old female and 21-year-old male patients. Both the cases had extralymphatic bone involvement in the form of solitary bone lesion. Initially, there was no leukemic involvement in both the cases, but the second case progressed to acute leukemia during the course of the disease. On immunophenotypic evaluation, both the cases revealed blasts showing unequivocal evidence of myeloid and B-lymphoid lineage commitment. These cases were difficult to categorize either into MPAL as the BM was not involved or into lymphoblastic lymphoma due to coexpression of myeloid differentiation. Therefore, we chose to classify them as a bi/mixed phenotypic blastic hematolymphoid neoplasm. Detailed immunophenotypic analysis either by immunohistochemistry or flow cytometric immunophenotyping is important for the diagnosis of such cases as they have a poor prognosis.

CD19 negative precursor B acute lymphoblastic leukemia (B-ALL)-Immunophenotypic challenges in diagnosis and monitoring: A study of three cases.

BACKGROUND: CD19 is a B-cell specific marker, expressed on all stages of B-lymphocytes including plasma cells. It is widely used in the flow cytometric immunophenotyping (FCI) of B-cell and plasma cell malignancies. The analysis approach of FCI for the diagnosis and monitoring of B-cell acute lymphoblastic leukemia (B-ALL) is totally based on the CD19-based primary gating strategy and it would be challenging to study B-ALL without CD19 expression. Since CD19 negative B-ALL are extremely rare, we report three cases of B-ALL with negative expression of CD19 and discussed its implication in the diagnosis, residual disease monitoring and future targeted therapy. METHODS: Peripheral blood (PB) and bone marrow (BM) samples from three cases suspicious of acute leukemia were studied for morphology, cytochemistry, immunophenotyping and cytogenetics. FCI was performed using a comprehensive six to eight-color multiparametric assay. The cytogenetic studies for standard recurrent genetic translocations were performed by FISH & Karyotyping. RESULTS: The three cases studied were diagnosed as B-ALL based on the expression of CD10, CD20, CD22, CD34, and CD79a by leukemic blasts. CD19 was studied using two different clones (i.e. J3-119 & HIB-19) and found to be severely down regulated in all three cases. There were no significant differentiating features in morphology. Cytogenetic studies were negative for recurrent translocations. CONCLUSION: We report three cases of extremely rare CD19 negative B-ALL. Lack of awareness of negative CD19 expression in B-ALL can leads to incorrect immunophenotypic diagnosis and monitoring of B-ALL, especially in laboratories using limited markers. © 2016 International Clinical Cytometry Society.