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Myeloproliferative neoplasms (MPNs) are clonal hematopoietic stem cell disorders characterized by the expansion of myeloid lineage cells. Chronic myeloid leukemia (CML) is characterized by a BCR-ABL1 fusion gene that causes constitutive tyrosine kinase activity. Polycythemia vera, essential thrombocythemia, and primary myelofibrosis (PMF) are frequently associated with driver mutations in genes such as JAK2, CALR, and MPL and are mutually exclusive of BCR-ABL1. Herein, we report the first case study of a patient diagnosed with accelerated-phase CML while undergoing treatment for initial JAK2 V617F–positive, BCR-ABL1-negative PMF. This finding emphasizes the importance of BCR-ABL1 testing in patients with an atypical BCR-ABL1-negative MPN disease course.

Myeloid-derived suppressor cells (MDSCs) represent phenotypically heterogeneous populations that suppress tumor-specific T-cell responses. MDSCs are produced from myeloid precursors in emergent states and are increased in several hematologic malignancies. We evaluated the differences in the levels and prognostic significance of MDSCs according to the clinical status of chronic myeloid leukemia (CML). The percentages and numbers of granulocytic (g)MDSCs and monocytic (m)MDSCs in peripheral blood (PB) and bone marrow (BM) aspirates were determined by five-color flow cytometry (HLA-DR/CD11b/CD15/CD33/CD14). The median BM-gMDSC% and PB-gMDSC% of the CML group were lower than those of the complete hematologic response (CHR) and control groups (P

Thromboelastography (TEG) provides assessment of global coagulation. The TEG6s (Haemonetics Corporation) is a newly developed cartridge-based system, fully automated and the first true point-of-care TEG. In this study, we evaluated the precision and established the reference intervals (RIs) for TEG6s.TEG assays were performed on the blood of healthy donors to determine RIs and on the QC materials for precision testing. The study design was developed in accordance with Clinical and Laboratory Standards Institute Guidelines.TEG6s precision testing yielded low variability except R, due to a low value for the mean. The newly established RIs of R, MA, and LY30 were similar to the manufacturer's RIs. Some were different, showing short K and increased α.This study has shown that TEG6s has high precision and each institution should verify the manufacturer's RIs before adopting TEG6s and establish RIs if necessary.

Lupus anticoagulant (LA) are commonly detected during SARS-CoV-2 infection. However, the relationship between LA and clinical significance is still unclear.A retrospective chart analysis was performed on COVID-19 patients who were tested for LA at our hospital from March 2020 to November 2021. We analyzed the patient's characteristics based on the result of the LA test. In addition, subgroup analysis performed the LA-positive group who had undergone serial LA tests.A total of 219 COVID-19 patients were enrolled in the study, 148 patients (67.6%) were positive for LA test. The LA-positive group received more treatment of high flow nasal cannula (LA-positive 73.0%, LA-negative 57.7%, p = 0.024). The LA-positive group showed prolonged aPTT, higher levels of CRP and fibrinogen (all p's 0.05). Among 148 LA-positive patients, 127 patients (86.5%) were found to be LA-positive within 10 days of SARS-CoV-2 positive, and LA-positive group confirmed a median time to LA loss of 10 days. However, there was a group that was negative for LA in the early stages of infection and became positive about 13 days later. A subgroup analysis showed that these patients had different characteristics due to their longer hospital stays and higher D-dimer levels.In COVID-19 patients, LA is expected to be associated to disease severity. Since the clinical significance of LA is different depending on the onset time of LA positivity, the LA test is suggested to be done at diagnosis of SARS-CoV-2 infection, even if LA is negative, follow-up test should be considered within 10 days.

Clonal cytopenia of undetermined significance (CCUS) is characterized by persistent cytopenias with genetic aberrations, which do not meet the diagnostic criteria for myelodysplastic syndrome (MDS). We aimed to compare the clinical and genetic characteristics of CCUS with lower-risk MDS and identify patients with CCUS with a high risk of progression. We performed targeted sequencing of bone marrow (BM) samples from patients with idiopathic cytopenia of undetermined significance (ICUS) (n = 139) and MDS (n = 226). Overall survival (OS) of patients with CCUS (n = 78) was worse than non-clonal ICUS (n = 61) and superior to lower-risk MDS (n = 99). Patients with CCUS showed similar characteristics to those with lower-risk MDS, except for higher haemoglobin, lower BM cellularity, and less frequent SF3B1 mutations. Lower haemoglobin, DDX41 (biallelic germline and somatic), ETV6, and RUNX1 mutations were independent prognostic factors for worse OS. Lower haemoglobin and DDX41 mutations were also associated with lower progression-free survival. Patients with CCUS with high-risk features showed similar or worse OS than patients with lower-risk MDS. Our findings suggest that patients with CCUS having certain clinical or genetic features should be regarded and treated as lower-risk MDS despite lacking significant dysplasia or MDS-associated chromosomal abnormalities.

Malignant cells can increase in number using immune escape mechanisms such as immune checkpoints. In this study, we evaluated the expression of an immune checkpoint programmed death 1 (PD-1) on T-cell subsets in chronic myeloid leukemia (CML). We obtained bone marrow aspirate samples from CML patients and from individuals without evidence of hematologic malignancies (controls). PD-1 expression on T-cell subsets was measured using flow cytometric analysis. PD-1 expression levels on CD8+ T-cells were significantly lower in complete hematologic response (CHR) than in controls, chronic phase, and blast phase (BP). In CML patients receiving imatinib and dasatinib, PD-1 expression levels on CD8+ T-cells were lower than that at diagnosis. PD-1 expression levels on CD8+ T-cells were positively correlated with quantitative levels of the BCR/ABL fusion gene. PD-1 expression levels on CD4+ T-cells were higher in BP than in CHR. PD-1 expression levels on CD4+ T-cells did not differ significantly according to different medications or quantitative BCR/ABL1 fusion gene levels. Low PD-1 expression on CD8+ T-cells might play a role in maintaining CHR in CML patients. Immune monitoring of PD-1 expression on CD8+ T-cells may predict the disease course. In cases of refractory disease or resistance to imatinib or dasatinib, the use of PD-1 inhibitors would be helpful.

Background Waldenström macroglobulinemia (WM) is a subset of lymphoplasmacytic lymphoma (LPL) with bone marrow (BM) involvement and an IgM monoclonal gammopathy of any level. We aimed to identify the clinical, laboratory, and BM findings of patients with WM and to evaluate the usefulness of CD154 for the diagnosis and prognosis of WM. Methods We reviewed the medical records and BM studies and/or flow cytometric immunotyping of 31 patients with untreated WM. Semiquantitative immunohistochemistry (CD20, CD138, tryptase, and CD154) of BM was performed. Results Only six patients presented with symptoms of hyperviscosity syndrome. Eleven patients had solid cancer and/or another hematologic malignancy. Mast cells (MC) increased in all samples, with some in close contact with tumor cells. Tryptase-positive MC (17.1/ high-power fields [HPF], 1.2–72.0/HPF) and CD154-positive MC (8.6/HPF, 0.1–31.1/HPF) were observed. The high CD154-positive MC (≥8.6/HPF) group showed a lower overall five-year survival rate than the low CD154-positive MC (

This retrospective study aimed to investigate the outcomes of allogeneic hematopoietic stem cell transplantation (HSCT) for childhood myelodysplastic syndrome (MDS). Thirty-six patients (low-grade MDS, 24; advanced MDS, 12) received HSCT at the Asan Medical Center over two decades (early period, 1997–2007; recent period, 2008–2017). The transplantation outcomes were analyzed according to disease status, conditioning regimen, various donor types, and period of HSCT. During a median follow-up of 5.6 (range, 1.4–21.1) years, the probability of overall survival (OS) and failure-free survival was 77% and 69%, respectively. The cumulative incidence of transplantation-related mortality (TRM) was 12%. Significantly reduced TRM and improved OS were observed in patients who received HSCT during the recent period vs. the early period (TRM, 4% vs. 30%, P = 0.021; OS, 87% vs. 50%, P = 0.006). Comparable outcomes were observed for HSCT from haploidentical family donors vs. HLA-identical donors (TRM, 10% vs. 14%, P = 0.837; OS, 86% vs. 79%, P = 0.625). This study identified the improved outcomes of allogeneic HSCT for childhood MDS over time, in addition, the feasible outcomes of haploidentical HSCT suggested its use as an attractive alternative in the future procedures.

Myelodysplastic/myeloproliferative neoplasm with ring sideroblasts and thrombocytosis (MDS/ MPN-RS-T) was newly introduced as a full entity in the 2016 revision of the WHO classification. In this study, we investigated the morphologic, laboratory, and clinical features of MDS/MPN-RS-T.We reviewed the bone marrow and genetic studies of patients whose diagnoses were coded as "refractory anemia with ring sideroblasts (RARS)" or "MDS/MPN, unclassifiable" between January 2008 and April 2018.A total of 8 cases fulfilled the criteria for a diagnosis of MDS/MPN-RS-T. All of them had no specific symptoms. Half of the cases had less than 450 × 109/L platelet counts by an automated hematology analyzer; however, all platelet counts exceeded 450 × 109/L when performed manually. JAK2 mutation tests were performed in 7 cases, and a heterozygous mutation was detected in 1 case. SF3B1 mutations were present in 3 of the 4 cases tested.When RARS is suspected in patients without thrombocytopenia, manual platelet counts should be performed. For patients with suspected essential thrombocythemia, RS evaluation through careful observation of an iron-stained slide is crucial. Since the independent evaluation of RS was reflected in the revised classification, the ambiguous disease classification becomes clearer and more consistent.

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).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.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).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.

Myeloid-derived suppressor cells (MDSCs) are heterogeneous populations of immature myeloid cells with immunosuppressive effects that have prognostic potential in patients with malignancies; however, survival analysis studies are sparse. In this study, the prognostic implication of MDSCs was investigated in peripheral blood (PB) and bone marrow (BM) samples from 81 patients with plasma cell myeloma at diagnosis. MDSCs were quantified as monocytic MDSCs (mMDSCs) (CD11b+HLA-DR−/lowCD14+) and granulocytic MDSCs with neutrophils (gMDSCs-N) (CD11b+HLA-DR−/lowCD14−CD33+CD15+). Serum creatinine and lactate dehydrogenase levels showed a moderate correlation with all MDSC types, except BM-gMDSCs-N; mMDSCs correlated with serum β2-microglobulin level, and PB-mMDSCs showed an inverse correlation with hemoglobin. PB-mMDSC levels were significantly higher in patients with progressive disease than those in patients at diagnosis and complete response. BM-mMDSC levels in patients with progressive disease were also higher than those in patients at diagnosis. Patients with high mMDSCs showed significantly poorer prognosis than patients with low mMDSCs. Multivariate analysis showed high PB-mMDSCs (≥0.3%) as a significant adverse prognostic marker for overall survival. This study demonstrated the independent adverse prognostic impact of PB-mMDSCs in patients with myeloma. PB-mMDSC measurement using whole blood is readily accessible in clinical laboratories, and may be used as a prognostic marker in clinical practice.

Background JL1, a CD43 epitope and mucin family cell surface glycoprotein, is expressed on leukemic cells. An anti-JL1 antibody combined with a toxic substance can have targeted therapeutic effects against JL1-positive leukemia; however, JL1 expression on bone marrow (BM) lymphoma cells has not been assessed using flow cytometry. We investigated JL1 expression on BM lymphoma cells from patients with non-Hodgkin lymphoma (NHL) to assess the potential of JL1 as a therapeutic target. Methods Patients with BM involvement of mature B-cell (N=44) or T- and natural killer (NK)-cell (N=4) lymphomas were enrolled from May 2015 to September 2016. JL1 expression on BM lymphoma cells was investigated using flow cytometry. Clinical, pathological, and cytogenetic characteristics, and treatment responses were compared according to JL1 expression status. Results Of the patients with NHL and BM involvement, 37.5% (18/48) were JL1-positive. Among mature B-cell lymphomas, 100%, 38.9%, 33.3%, 100%, and 25.0% of Burkitt lymphomas, diffuse large B-cell leukemias, mantle cell leukemias, Waldenstrom macroglobulinemia, and other B-cell lymphomas, respectively, were JL1-positive. Three mature T- and NK-cell NHLs were JL1-positive. JL1 expression was associated with age (P=0.045), complete response (P=0.004), and BM involvement at follow-up (P=0.017), but not with sex, performance status, the B symptoms, packed marrow pattern, cytogenetic abnormalities, or survival. Conclusions JL1 positivity was associated with superior complete response and less BM involvement in NHL following chemotherapy.

POEMS syndrome is a rare paraneoplastic syndrome, which includes polyneuropathy, organomegaly, endocrinopathy, M-protein, and skin changes due to plasma cell (PC) neoplasm. Diagnosis of this disease is challenging because of its rarity and complex clinical manifestations. We attempted to identify the key clinical features and characteristic bone marrow (BM) findings of POEMS syndrome, by reviewing the medical records and BM analyses of 24 Korean patients. Frequent clinical manifestations included polyneuropathy (100%), monoclonal gammopathy (100%), organomegaly (92%), extravascular volume overload (79%), and endocrinopathy (63%). The BM analyses revealed mild PC hyperplasia (median PCs: 5.5%) and frequent megakaryocytic hyperplasia (88%), megakaryocyte clusters (88%), and hyperlobation (100%). Flow cytometry of BM aspirates using CD138/CD38/CD45/CD19/CD56 showed normal (67%, 4/6) or neoplastic PC immunophenotypes (33%, 2/6). A diagnosis of POEMS syndrome must be considered when a patient suspected of having PC dyscrasia shows the above clinical presentation and BM findings.

BACKGROUND Possible correlations between the expression of immune checkpoint molecules and prognosis in childhood acute leukemia were investigated. MATERIALS AND METHODS The expression of programmed-death 1 (PD1), cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), and B- and T-lymphocyte attenuator (BTLA) was determined by flow cytometry on peripheral αβ+ and γδ+ T-cells from patients with newly diagnosed acute lymphoblastic leukemia (ALL) (n=9) or acute myeloid leukemia (AML) (n=12), and from healthy volunteers (n=7). The expression of programmed-death ligand 1 (PD-L1), B7-1, B7-2, human leukocyte antigen-ABC (HLA-ABC), and herpesvirus-entry mediator (HVEM) ligands was determined on leukemia blasts. RESULTS PD1 expression on αβ+ and γδ+ T-cells was significantly higher in patients with ALL than in those with AML (p=0.0019 and 0.0239, respectively). CTLA-4 expression was moderately higher on αβ+ and γδ+ T-cells in ALL (p=0.077 and 0.077, respectively), whereas HLA-ABC expression was significantly higher in AML blast cells (p=0.0182). The expression of CTLA-4 on γδ+ T-cells and the B7-2 ligand on blasts was higher in patients with high-risk ALL (p=0.02 and 0.02, respectively). In AML, PD1 expression on αβ+ T-cells was higher in the intermediate-risk group (p=0.05), whereas HVEM expression was significantly higher in the low-risk group (p=0.02). Expression of CTLA-4 on γδ+ T-cells and PD-L1 on blasts were both associated with poor relapse-free survival outcomes in ALL (p=0.049). CONCLUSION The higher expression of immune checkpoint molecules, in particular, CTLA-4 and PD-L1 are associated with a poorer prognosis in ALL, suggesting that selective use of the immune checkpoint blockade might improve the clinical outcomes in patients with ALL.

Haploidentical family donors have been used as an alternative source in hematopoietic cell transplantation for patients with severe aplastic anemia. We evaluated and compared the outcomes of transplantation in pediatric acquired severe aplastic anemia based on donor type. Sixty-seven patients who underwent transplantation between 1998 and 2017 were included. Fourteen patients received grafts from matched sibling donors, 21 from suitable unrelated donors, and 32 from haploidentical family donors. Ex vivo CD3+ or αβ+ T cell–depleted grafts were used for haploidentical transplantation. Sixty-five patients (97.0%) achieved neutrophil engraftment at a median of 11 days. Haploidentical transplantation resulted in significantly faster neutrophil engraftment at a median of 10 days, compared with 14 days in cases of matched sibling donors and 12 days in cases of unrelated donor recipients. Nine patients experienced graft failure, and 5 of 7 who underwent a second transplantation are alive. There was no difference in the incidence of acute or chronic graft-versus-host disease based on donor type. The 5-year overall survival and failure-free survival rates were 93.8% ± 3.0% and 83.3% ± 4.6%, respectively, and there was no significant survival difference based on donor type. The survival outcomes of haploidentical transplantation in patients were comparable with those of matched sibling or unrelated donor transplantation. Optimized haploidentical transplantation using selective T cell depletion and conditioning regimens including low-dose total body irradiation for enhancing engraftment may be a realistic therapeutic option for pediatric patients with severe aplastic anemia.

Background JL1 is a newly identified CD43 epitope that specifically recognizes leukemic cells. We analyzed the incidence of JL1 expression and compared the clinical, immunophenotypic, and genetic characteristics of de novo pediatric acute leukemia patients with respect to JL1 expression status to determine the therapeutic potential of an anti-JL1 antibody. Methods Seventy-eight patients with pediatric acute leukemia (52 with ALL, 26 with AML) diagnosed between December 2014 and January 2016 were enrolled prospectively. Flow cytometry for JL1 expression was performed at diagnosis. Clinical, immunophenotypic, and genetic characteristics were compared with respect to JL1 expression status by the Student t-test/Mann-Whitney U test and chi-square test/Fisher's exact test. Results The incidence of JL1 expression was 76.9% and 84.6% in ALL and AML patients, respectively. ALL patients with JL1 expression showed higher CD10 and cytoplasmic IgM expressions than those without JL1 expression (P=0.022 and 0.003, respectively) and were associated with TCF3-PBX1 and KMT2A-MLLT1 translocations. AML patients with JL1 expression showed higher CD13 and lower CD65 and CD15 expressions than those without JL1 expression (P=0.013, 0.007, and 0.024, respectively) and were associated with RUNX1-RUNX1T1, PML-RARA, and CBFB-MYH11 translocations. The JL1 expression incidence did not differ between ALL and AML, and the JL1 expression status did not affect prognosis. Conclusions Our findings support the potential therapeutic role of anti-JL1 monoclonal antibodies; JL1 expression was associated with specific immunophenotypes and genetic abnormalities. Future studies should examine the prognostic impact of JL1 expression in pediatric acute leukemias.

Affordable point-of-care (POC) CD4 + T lymphocyte counting techniques have been developed as alternatives to flow cytometry-based instruments caring for patients with human immunodeficiency virus (HIV)-1. However, POC CD4 enumeration technologies can be inaccurate. Here, we developed a microparticle-based visual detector of CD4 + T lymphocytes (ImmunoSpin) using microparticles conjugated with anti-CD4 antibodies, independent of microfluidic or fluorescence detection systems. Visual enumeration of CD4 + T cells under conventional light microscope was accurate compared to flow cytometry. Microparticle-tagged CD4 + T cells were well-recognized under a light microscope. ImmunoSpin showed very good precision (coefficients of variation of ImmunoSpin were ≤ 10%) and high correlation with clinical-grade flow cytometry for the enumeration of CD4 + T cells (y = 0.4232 + 0.9485 × for the %CD4 + T cell count, R2 = 0.99). At thresholds of 200 and 350 cells/µL, there was no misclassification of the ImmunoSpin system compared to the reference flow cytometry. ImmunoSpin showed clear differential classification of CD4 + T lymphocytes from granulocytes and monocytes. Because non-fluorescence microparticle-tags and cytospin slides are used in ImmunoSpin, they can be applied to an automatic digital image analyzer. Slide preparation allows long-term storage, no analysis time limitations, and image transfer in remote areas. Graphical abstract

Purpose Monocyte distribution width (MDW) has been suggested as an early biomarker of sepsis, but few studies have compared MDW with conventional biomarkers, including C-reactive protein (CRP) and procalcitonin (PCT). This study evaluated MDW as a biomarker for sepsis and compared it with CRP and PCT. Materials and methods Patients aged 18–80 years who visited the emergency department were screened and prospectively enrolled in a tertiary medical center. Complete blood count, MDW, CRP, and PCT were examined. Diagnostic performance for sepsis was tested using the area under the curve (AUC) of receiver operating characteristic (ROC) curves, sensitivity, and specificity. Results In total, 665 patients were screened, and 549 patients with valid laboratory test results were included in the analysis. The patients were categorized into three groups according to the Sepsis-3 criteria: non-infection, infection, and sepsis. MDW showed the highest value in the sepsis group (median [interquartile range], 24.0 [20.8–27.8]). The AUC values for MDW, CRP, PCT, and white blood cells for predicting sepsis were 0.71 (95% confidence interval [CI], 0.67–0.75), 0.75 (95% CI, 0.71–0.78], 0.76 (95% CI, 0.72–0.79, and 0.61 (95% CI, 0.57–0.65), respectively. With the optimal cutoff value of the cohort, the sensitivity was 83.0% for MDW (cutoff, 19.8), 69.7% for CRP (cutoff, 4.0), and 76.6% for PCT (cutoff, 0.05). The combination of quick Sequential Organ Failure Assessment (qSOFA) with MDW improved the AUC (0.76; 95% CI, 0.72–0.80) to a greater extent than qSOFA alone (0.67; 95% CI, 0.62–0.72). Conclusions MDW reflected a diagnostic performance comparable to that of conventional diagnostic markers, implying that MDW is an alternative biomarker. The combination of MDW and qSOFA improves the diagnostic performance for early sepsis.

DDX41 mutations are associated with hematologic malignancies including myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), but the incidence in idiopathic cytopenia of undetermined significance (ICUS) is unknown. We investigated the incidence, genetic characteristics, and clinical features of DDX41 mutations in Korean patients with ICUS, MDS, or AML. We performed targeted deep sequencing of 61 genes including DDX41 in 457 patients with ICUS (n=75), MDS (n=210), or AML (n=172). Germline DDX41 mutations with causality were identified in 28 (6.1%) patients, of whom 27 (96.4%) had somatic mutations in the other position of DDX41. Germline origins of the DDX41 mutations were confirmed in all of the 11 patients in whom germline-based testing was performed. Of the germline DDX41 mutations, p.V152G (n=10) was most common, followed by p.Y259C (n=8), p.A500fs (n=6), and p.E7* (n=3). Compared with non-mutated patients, patients with a DDX41 mutation were more frequently male, older, had a normal karyotype, low leukocyte count, and hypocellular marrow at diagnosis. Three of the four ICUS patients with germline DDX41 mutations progressed to MDS. The incidence of DDX41 mutations in Korean patients was high and there was a distinct mutation pattern, in that p.V152G was a unique germline variant. ICUS harboring germline DDX41 mutations may be regarded as a hereditary myeloid neoplasm. Germline DDX41 mutations are not uncommon and should be explored when treating patients with myeloid malignancies.

Background Plasma cell myeloma (PCM) is caused by immune dysregulation. We evaluated the expression of immune checkpoint programmed cell death protein-1 (PD-1) on T cell subsets in PCM patients according to disease course and cytogenetic abnormalities. This study aimed to find a target group suitable for therapeutic use of PD-1 blockade in PCM. Methods A total of 188 bone marrow (BM) samples from 166 PCM patients and 32 controls were prospectively collected between May 2016 and May 2017. PD-1 expression on BM T cell subsets was measured using flow cytometry. Results At diagnosis, the median PD-1 expression on CD4+ T cells was 24.6%, which did not significantly differ from that in controls. After stem cell transplantation, PD-1 expression on CD4+ T cells was higher than that at diagnosis (P

Assessment of bone marrow (BM) involvement in peripheral T-cell lymphoma, not otherwise specified (PTCL) is straightforward in cases of extensive involvement but difficult in cases of minimal to partial involvement. We evaluated the usefulness of CD3 as an immunohistochemical marker for assessing BM involvement in PTCL patients. BM biopsies of 92 PTCL patients were immunohistochemically stained for CD3, CD4, CD8, CD20, and CD56, and evaluated by two hematopathologists. CD3 positivity was graded according to the proportion of CD3-positive cells and the number of CD3-positive cells in a cluster. These criteria were used to determine the cut-offs at which significant differences in progression-free survival (PFS) and overall survival (OS) were observed. Multivariate analysis controlling the International Prognostic Index (IPI) score and its individual factors revealed that >20 CD3-positive cells in a cluster adversely affected PFS (relative risk [RR], 2.1; 95% confidence interval [CI], 1.0-4.3; P=0.047) and OS (RR, 2.4; 95% CI, 1.1-5.1; P=0.028) independent of IPI score. A cluster with >20 CD3-positive cells is a candidate indicator for BM involvement in PTCL.