Chapter 13: Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus

Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus provides an in-depth exploration of the pathology, etiology, and clinical manifestations of diseases affecting white blood cells, lymph nodes, the spleen, and the thymus. The text begins by establishing the fundamentals of normal hematopoiesis before delving into non-neoplastic leukocyte disorders, including leukopenias such as neutropenia and agranulocytosis, alongside reactive cellular proliferations like leukocytosis, acute and chronic nonspecific lymphadenitis, and hemophagocytic lymphohistiocytosis. The primary focus of the chapter centers on the complex landscape of hematologic malignancies, meticulously detailing the genetic, chromosomal, and environmental driver mutations responsible for white cell neoplasia. It systematically categorizes lymphoid neoplasms into precursor B-cell and T-cell tumors, notably acute lymphoblastic leukemia and lymphoma, as well as mature peripheral B-cell neoplasms such as chronic lymphocytic leukemia, follicular lymphoma, diffuse large B-cell lymphoma, Burkitt lymphoma, and mantle cell lymphoma. Peripheral T-cell and natural killer cell malignancies are also thoroughly examined, encompassing conditions like mycosis fungoides, Sézary syndrome, and anaplastic large-cell lymphoma. Furthermore, the text distinguishes non-Hodgkin lymphomas from Hodgkin lymphoma, highlighting the latter's unique Reed-Sternberg cells and its specific clinicopathologic subtypes. Plasma cell dyscrasias, prominently multiple myeloma and its associated skeletal and renal complications, alongside monoclonal gammopathy of undetermined significance, are extensively detailed. Transitioning to myeloid neoplasms, the chapter provides comprehensive insights into acute myeloid leukemia, myelodysplastic neoplasms characterized by ineffective hematopoiesis, and myeloproliferative neoplasms driven by mutated tyrosine kinases, including chronic myeloid leukemia, polycythemia vera, essential thrombocythemia, and primary myelofibrosis. The text also covers rare macrophage and dendritic cell disorders such as Langerhans cell histiocytosis. Concluding with the secondary lymphoid organs, the chapter outlines splenic pathologies including congestive splenomegaly, hypersplenism, splenic infarcts, and traumatic rupture, before finishing with an overview of thymic developmental anomalies, thymic hyperplasia associated with autoimmune conditions like myasthenia gravis, and thymic epithelial tumors known as thymomas.