Cavity-based lymphomas: challenges and novel concepts. A report of the 2022 EA4HP/SH lymphoma workshop.

The 2022 European Association for Haematopathology/Society for Hematopathology lymphoma workshop session on cavity-based lymphomas included sixty-eight cases in seven sections. The disease entities discussed include primary effusion lymphomas (PEL), extracavitary primary effusion lymphomas and confounding entities (ECPEL), HHV8-negative B-lineage lymphomas-effusion based (EBV-negative, EBV-positive, and plasmablastic types), diffuse large B-cell lymphoma associated with chronic inflammation, fibrin-associated diffuse large B-cell lymphoma (FA-DLBCL), breast implant-associated anaplastic large cell lymphoma (BIA-ALCL), and other lymphomas presenting as an effusion. All entities above are discussed; however, three are delved into greater detail given the challenges with classification: ECPEL, HHV8-negative effusion-based lymphomas, and FA-DLBCL. Cases exemplifying the diagnostic difficulty in differentiating ECPEL from HHV8-positive diffuse large B-cell lymphoma and germinotropic lymphoproliferative disorder were discussed. The more recently recognized effusion-based HHV8-negative large B-cell lymphoma is explored, with several cases submitted raising the question if this subset should be carved out as a specific entity, and if so, what should be the refining diagnostic criteria. Case submissions to the FA-DLBCL section yielded one of the largest case series to date, including classic cases, cases furthering the discussion on disease sites and prognosis, as well as novel concepts to be considered in this entity. The 2022 EA4HP/SH workshop cases allowed for further confirmation of the characteristics of some of the more historically accepted cavity-based lymphomas, as well as further inquiry and debate on relatively new or evolving entities.

Fatal Microangiopathic Hemolytic Anemia Due to Sézary Syndrome.

Sézary syndrome (SS) is a form of cutaneous T-cell lymphoma (CTCL), demonstrating leukemic involvement of malignant T-cells. Known systemic sequelae of SS include hemophagocytic syndrome-induced anemia, normocytic anemia secondary to bone marrow infiltration, and pancytopenia. We report a patient with SS, initially demonstrating widespread morbilliform eruption, who presented with malignancy-related microangiopathic hemolytic anemia (MAHA). Our findings represent a novel presentation of SS that will inform the differential diagnosis and treatment of future SS patients presenting with anemia and thrombocytopenia.

Secondary cytogenetic abnormalities in core-binding factor AML harboring inv(16) vs t(8;21).

Patients with core-binding factor (CBF) acute myeloid leukemia (AML), caused by either t(8;21)(q22;q22) or inv(16)(p13q22)/t(16;16)(p13;q22), have higher complete remission rates and longer survival than patients with other subtypes of AML. However, ∼40% of patients relapse, and the literature suggests that patients with inv(16) fare differently from those with t(8;21). We retrospectively analyzed 537 patients with CBF-AML, focusing on additional cytogenetic aberrations to examine their impact on clinical outcomes. Trisomies of chromosomes 8, 21, or 22 were significantly more common in patients with inv(16)/t(16;16): 16% vs 7%, 6% vs 0%, and 17% vs 0%, respectively. In contrast, del(9q) and loss of a sex chromosome were more frequent in patients with t(8;21): 15% vs 0.4% for del(9q), 37% vs 0% for loss of X in females, and 44% vs 5% for loss of Y in males. Hyperdiploidy was more frequent in patients with inv(16) (25% vs 9%, whereas hypodiploidy was more frequent in patients with t(8;21) (37% vs 3%. In multivariable analyses (adjusted for age, white blood counts at diagnosis, and KIT mutation status), trisomy 8 was associated with improved overall survival (OS) in inv(16), whereas the presence of other chromosomal abnormalities (not trisomy 8) was associated with decreased OS. In patients with t(8;21), hypodiploidy was associated with improved disease-free survival; hyperdiploidy and del(9q) were associated with improved OS. KIT mutation (either positive or not tested, compared with negative) conferred poor prognoses in univariate analysis only in patients with t(8;21).

Impact of Double- or Triple-Hit Pathology on Rates and Durability of Radiation Therapy Response Among Patients With Relapsed or Refractory Large B-Cell Lymphoma.

PURPOSE: Double-hit lymphomas and triple-hit lymphomas (DHL/THL), also known as high-grade B-cell lymphoma with MYC and BCL2 or BCL6 rearrangements, are associated with chemoresistance and inferior survival. However, whether radiation therapy (RT) efficacy is altered in DHL/THL is less well characterized. Among patients with relapsed or refractory large B-cell lymphoma (R/R LBCL), we compared rates and durability of response between patients with and without DHL/THL. METHODS AND MATERIALS: We retrospectively reviewed consecutive R/R LBCL patients who were irradiated at a single institution from January 2008 to June 2017. Patients in whom c-MYC rearranged status was known were evaluated for response to RT, in-field control, progression-free, and overall survival. RESULTS: Among 245 irradiated patients with LBCL, 41 patients with confirmed c-MYC status were treated for R/R disease (14 DHL/THL, 27 non-DHL/THL) and formed our cohort. Compared with non-DHL/THL, more DHL/THL patients had progressive disease at RT (71% vs 48%), had larger gross tumor volumes (GTV; median 696 mL vs 117 mL), and were treated with palliative intent (71% vs 41%). Despite similar RT doses (median 35 Gy), radiographic complete response rate was lower among DHL/THL patients: 14.3% versus 64.7% (P = .01). With a median 2 years of follow-up, one in-field failure was observed in each group. DHL/THL patients had inferior progression-free survival (7% vs 46%; P = .02) and overall survival (14% vs 68%; P = .03) at 6 months. CONCLUSIONS: R/R LBCL is responsive to RT, although rates of response are lower among DHL/THL patients. Given poor survival after RT, in-field control was hard to evaluate in this cohort. Larger cohorts are required to better elucidate whether differences in response rates are driven by larger disease burden at RT versus tumor biology. These findings are of increasing pertinence in light of use of RT as bridging therapy to cellular immunotherapies.

Flow cytometric features of incidental indolent T lymphoblastic proliferations.

Indolent T lymphoblastic proliferations have been reported rarely in extramedullary and extrathymic tissues. Recent work has identified these indolent T lymphoblast populations to be mostly CD4+/CD8+ (characterized by immunohistochemistry), with only limited immunophenotypic evaluation of these populations by flow cytometry (FC). We retrospectively reviewed our institutional FC archives and identified 12 samples from 10 patients with incidental T lymphoblastic populations. Samples were characterized with respect to expression of T-cell antigens, CD45, TdT, CD1a, and T/NK antigens, and light scatter properties. Overall, the proportion of T lymphoblasts was small (range 0.01-8.8% of white cells; mean, 1.7%). Histologic correlation showed scattered immature T lymphoblasts in samples without overt distortion of underlying architecture. T lymphoblasts were identified most frequently in association with Castleman disease (four) or tissues with Castleman features (four), marginal zone B-cell lymphoma (one), or tissue with reactive/atypical changes (three cases). Although three cases were composed predominantly of CD4+/CD8+ T cells, the majority of cases in our cohort (eight) included a major subset of CD4-/CD8- T lymphoblasts by FC (one case CD8+/CD4-), which has not been described previously. There was no evidence of subsequent progression to T lymphoblastic leukemia. Incidental, indolent T lymphoblastic proliferations may be detected by clinical FC. In contrast to reports, we find that these proliferations in clinical samples may contain not only CD4+/CD8+ immature T cells but also CD4-/CD8- immature T cells, expanding the immunophenotypic spectrum of this entity.

Flow Cytometry for Non-Hodgkin and Hodgkin Lymphomas.

Multiparametric flow cytometry is a powerful diagnostic tool that permits rapid assessment of cellular antigen expression to quickly provide immunophenotypic information suitable for disease classification. This chapter describes a general approach for the identification of abnormal lymphoid populations by flow cytometry, including B, T, NK, and Hodgkin lymphoma cells suitable for the clinical and research environment. Knowledge of the common patterns of antigen expression of normal lymphoid cells is critical to permit identification of abnormal populations at disease presentation and for minimal residual disease assessment. We highlight an overview of procedures for processing and immunophenotyping non-Hodgkin B- and T-cell lymphomas and also describe our strategy for the sensitive and specific diagnosis of classical Hodgkin lymphoma and nodular lymphocyte predominant Hodgkin lymphoma.

Pattern associated leukemia immunophenotypes and measurable disease detection in acute myeloid leukemia or myelodysplastic syndrome with mutated NPM1.

BACKGROUND: The presence of measurable residual disease after therapy is a significant risk factor of relapse in patients with acute myeloid leukemia (AML). By detecting cells with leukemia-associated immunophenotype (LAIP), multiparameter flow cytometry (MFC) can detect residual leukemia at a level significantly lower than that detected by morphology. However, changes in LAIPs during or after therapy may pose a challenge to MRD testing. AML with mutated NPM1 represents the largest subtype of AML sharing a common leukemogenic mechanism and similar LAIPs. Here, we identified a common pattern of LAIPs in myeloid blasts with mutated NPM1, and studied its stability and limit of detection after therapy. METHODS: We summarized aberrancies of leukemic blasts with mutated NPM1 at diagnosis in 61 patients and paired relapse in 25 patients. In addition, we examined the detection of leukemic blasts in 590 specimens collected from 152 patients in complete remission after induction for AML/MDS-EB with mutated NPM1. RESULTS: Our findings demonstrate myeloid blasts with mutated NPM1 have a characteristic pattern of LAIPs that is present in nearly all cases of AML/MDS-EB with mutated NPM1 at initial diagnosis and relapse, regardless of morphologic variations, FLT3 ITD status, or karyotype abnormality. The myeloid blasts with mutated NPM1 can be detected at an approximate level of 0.1% of total leukocytes in morphologic remission with high specificity validated by clinical outcome. CONCLUSION: The characteristic pattern of LAIPs of myeloid blasts with mutated NPM1 is common and stable, and allows sensitive and specific detection of AML or MDS with mutated NPM1 after therapy. © 2018 International Clinical Cytometry Society.

Macrophage activation syndrome in a patient with axial spondyloarthritis on adalimumab.

Macrophage activation syndrome (MAS) is a rare and potentially fatal condition characterized by excessive activation and uncontrolled proliferation of T lymphocytes and macrophages, leading to overwhelming systemic inflammation and cytokine release. MAS has been reported with viral infections, autoimmune disorders, malignancies, and medications. We describe a case of a patient with axial spondyloarthritis (axSpA) treated with adalimumab, who presented with MAS.

Core-binding factor acute myeloid leukemia with t(8;21): Risk factors and a novel scoring system (I-CBFit).

BACKGROUND: Although the prognosis of core-binding factor (CBF) acute myeloid leukemia (AML) is better than other subtypes of AML, 30% of patients still relapse and may require allogeneic hematopoietic cell transplantation (alloHCT). However, there is no validated widely accepted scoring system to predict patient subsets with higher risk of relapse. METHODS: Eleven centers in the US and Europe evaluated 247 patients with t(8;21)(q22;q22). RESULTS: Complete remission (CR) rate was high (92.7%), yet relapse occurred in 27.1% of patients. A total of 24.7% of patients received alloHCT. The median disease-free (DFS) and overall (OS) survival were 20.8 and 31.2 months, respectively. Age, KIT D816V mutated (11.3%) or nontested (36.4%) compared with KIT D816V wild type (52.5%), high white blood cell counts (WBC), and pseudodiploidy compared with hyper- or hypodiploidy were included in a scoring system (named I-CBFit). DFS rate at 2 years was 76% for patients with a low-risk I-CBFit score compared with 36% for those with a high-risk I-CBFit score (P < 0.0001). Low- vs high-risk OS at 2 years was 89% vs 51% (P < 0.0001). CONCLUSIONS: I-CBFit composed of readily available risk factors can be useful to tailor the therapy of patients, especially for whom alloHCT is not need in CR1 (ie, patients with a low-risk I-CBFit score).

Small, abnormal B lymphoid blast populations in chronic myelogenous leukemia at diagnosis: Does this finding indicate an accelerated course?

BACKGROUND: The 2008 WHO is not specific regarding subclassification of chronic myelogenous leukemia (CML) with less than 20% abnormal B lymphoid blasts (ABLB), and suggests patients with ABLB often show rapid progression (Swerdlow, 2008). Recent studies have shown variable outcomes when small abnormal B cell populations are seen by flow cytometry (El Rassi et al., Cancer 2015; 121:872-875; Vrotsos et al., Cytometry B Clin Cytom 2015). METHODS: The hematopathology database was searched (7.4-year period), and patients identified through routine clinical study, who were BCR-ABL1 positive CML and had an ABLB of less than 20%. Flow cytometric (FC) and histologic data was evaluated to determine immunophenotypic abnormalities, immunohistochemical patterns, and percentage of ABLB, hematogones, and mature B cells. RESULTS: Seven patients with CML and ABLB identified by FC studies were found, five of which also had available histologic material to review. ABLB by FC ranged from 0.006% to 3.4%, typically demonstrated an immunophenotype with increased CD10, increased CD19, and decreased CD38, without myeloid antigens, abnormalities similar to that reported previously (Vrotsos et al., Cytometry B Clin Cytom 2015). The ABLB population was found only in diagnostic samples and always with more numerous hematogones. By immunohistochemistry, three of five patients showed ≥10% TdT positive cells. All patients showed a response to tyrosine kinase inhibitor therapy, and no patients progressed to clinical lymphoid blast phase. CONCLUSIONS: Immature B cells, occasionally including a small subset with an abnormal phenotype can be observed in chronic phase CML at diagnosis. We believe an approach incorporating clinical data, cytogenetic/molecular findings, and morphologic evaluation may be helpful when determining the best management of CML patients at diagnosis if small ABLB populations are identified by FC. © 2016 Clinical Cytometry Society.

Interactive Tutorial of Normal Lymph Node Histology for Pathology and Laboratory Medicine Residents and Medical Students.

INTRODUCTION: Computer-based e-learning modules have been shown to be an effective learning tool in medical education. However, readily available, interactive, computer-based modules specifically educating on the histology of the normal lymph node have not been developed. METHODS: Using Microsoft PowerPoint, I developed a macro-enabled slide show illustrating and describing the architectural, cytomorphologic, and immunophenotypic features of the normal lymph node. This resource can be made available to medical students and residents prior to their hematopathology service rotation, as well as during their rotation should they want to review the module. The tutorial is interactive, with mixed-media features, links to pre- and postquizzes, and an interactive quiz at the end to solidify understanding and address areas of confusion. RESULTS: After 1 year of elective implementation, eight out of 13 students chose to use the tutorial, four of whom gave formal feedback in the form of a survey and three verbal feedback. All feedback was positive, finding the tutorial a useful adjunct. DISCUSSION: Although extensive implementation was limited given the small numbers that rotate through the hematopathology service on a yearly basis, an interactive, computer-based module was found helpful by the students in learning normal lymph node histology. This 1-year experience demonstrated that the normal lymph node tutorial can be used as an effective adjunct in educating pathology residents and medical students on normal lymph node cytomorphology and immunoarchitecture in the context of a busy clinical patient care setting. Continued learner feedback will be necessary to further enhance the quality of this platform for education.