A 50-year-old man presents with fatigue and easy bruising. A complete blood count and peripheral blood smear shows leukocytosis with 56% circulating blasts. The patient has no previous history of myeloid neoplasm or treatment with chemotherapy. Which of the following findings would definitively establish a diagnosis of acute myeloid leukemia?

This chapter provides a comprehensive review of benign hematopoietic disorders affecting white blood cells and platelets. The chapter focuses on acquired and inherited conditions that lead to qualitative and quantitative defects in neutrophils, monocytes, and platelets. Topics include reactive neutrophilia and lymphocytosis, acquired and congenital neutropenia, inherited bone marrow failure syndromes associated with neutropenia and/or thrombocytopenia, and sources of laboratory error in automated white blood cell and platelet counts.

The dense granules of platelets contain many molecules. Which of the following is found in dense granules?

Regarding a normal secondary follicle in a lymph node:

Which of the following statements is true regarding monoclonal B-cell lymphocytosis (MBL)?

A 55-year-old Caucasian woman presents for evaluation of fatigue. The patient states that her symptoms have been present for approximately 8 months and reports two episodes of cellulitis over the last year. Physical examination reveals mild splenomegaly; no skin lesions, lymphadenopathy, or other abnormalities are identified. Review of a complete blood count and peripheral blood smear shows absolute neutropenia, normocytic, normochromic anemia, and mild absolute lymphocytosis composed of numerous large lymphocytes with abundant cytoplasm and prominent red-pink granules. Which of the following is the most likely diagnosis?

The following are features of normal erythropoiesis except.

This chapter discusses the clinicopathologic features of a unique subgroup of aggressive B-cell lymphoma with plasmablastic morphology and immunophenotype, including plasmablastic lymphoma, primary effusion lymphoma, KSHV/HHV8-positive diffuse large B-cell lymphoma (DLBCL), and ALK-positive large B-cell lymphoma. The differential diagnosis among these entities and their key immunophenotypic features, particularly using multiparametric flow cytometric analysis, are compared and highlighted in detail. Differential diagnosis with other unrelated malignant neoplasms such as plasmablastic plasma cell myeloma, immunoblastic variant of DLBCL, non-hematopoietic neoplasms, anaplastic large cell lymphoma, and several other benign and malignant diseases/conditions resembling diagnostic mimics and pitfalls are also discussed.

This chapter describes the normal maturation pattern of plasmacytoid dendritic cells (pDCs), as well as the dynamic antigenic changes during pDC differentiation. Common markers used to define the pDC lineage are included, with their advantages and limitations discussed. Key immunophenotypic features associated with neoplastic pDC proliferations (blastic plasmacytoid dendritic cell neoplasm, myeloid neoplasms with plasmacytoid dendritic cell differentiation, and mature plasmacytoid dendritic cell proliferation associated with myeloid neoplasm) are covered. Minimal residual disease evaluation of pDC neoplasms is also discussed. Finally, the differential diagnosis associated with pDC proliferations is addressed.

nTFHL is a heterogenous group of mature T-cell lymphomas with follicular helper T-cell (TFH) immunophenotype. It is designated when at least two of the following markers are expressed: CD10, PD1 (CD279), ICOS, BCL6, CXCL13, CXCR5, SAP, MAF, or CD200. It is characterized by frequent loss of surface CD3, almost exclusively CD4, frequently diminished CD7, and retained CD2 and CD5. TFH markers studied by flow cytometry include CD10, PD1, CD200, ICOS, and CXCR5, but they can be expressed in reactive T-cells. nTFHL has three morphologic subtypes: angioimmunoblastic, follicular, and not otherwise specified. nTFHL angioimmunoblastic type or angioimmunoblastic T-cell lymphoma (AITL) is the prototype. All three subtypes share similar immunophenotypic characteristics, indistinguishable by flow cytometry. In nFFHL, lymphoma cells are frequently detected in blood and bone marrow by flow cytometry, often without morphologic involvement by lymphoma. The nTFHL immunophenotype is detailed and differential diagnoses are reviewed. Lymphocyte-variant hypereosinophilic syndrome and CD10-positive reactive T-cells in healthy individuals are discussed as immunophenotypic mimickers of nTFHLs.

Chimeric antigen receptor (CAR) T-cell therapy represents a revolution in cancer immunotherapy. Currently, seven FDA-approved CAR T-cell therapies target hematological malignancies such as B-cell lymphoblastic leukemia (B-ALL), B-cell lymphoma, and multiple myeloma. More than 250 ongoing clinical trials are exploring its application in various cancers. This rapid progress highlights the urgent need for dynamic and reliable monitoring of CAR T cells. Multiparameter flow cytometry (MFC) plays a critical role in quality control during manufacturing and also enables the detection of live CAR T cells after infusion in tracking and quantifying CAR T cells in vivo. By incorporating disease markers, MFC also provides a fast and accurate tool in addressing clinical concerns of disease relapse versus CAR T-cell proliferations. This chapter provides an overview of CART construction, recent developments, and clinical applications, followed by the introduction and illustration of CAR T by MFC tests as Laboratory Development Tests (LDT). Of the latter, we focus on CAR-CD19, CAR-BCMA, and allogeneic CART assays and discuss reagent choice, assay set-up, validations, and applications.