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WHAT WE DO
Hematopathology is one of the most diverse areas of pathology, since it represents a hybrid discipline involving clinical pathology (i.e., laboratory medicine) and anatomic pathology (surgical pathology of lymph nodes and extranodal tissues involved by hematolymphoid disorders). This field of pathology also uses cytomorphology and histology in combination with numerous ancillary tools (i.e., enzyme cytochemical and immunohistochemical staining, flow cytometric immunophenotyping, and cytogenetic and molecular techniques) in diagnosing and prognosticating hematolymphoid disorders. In some instances, the appropriate diagnosis of the hematolymphoid disorder also relies heavily on clinical and radiologic data.
For example, acute promyelocytic leukemia (APL) (as described later in this chapter) has characteristic cytomorphological, enzyme cytochemical, and flow cytometric immunophenotypic features that are defined by the ever-present t(15;17)(q24;21) or similar chromosomal variant. This translocation may be detected most rapidly by fluorescence in situ hybridization (FISH) performed in the cytogenetics laboratory. It is important to recognize this subtype of acute myeloid leukemia (AML) as soon as possible, since it is often associated with disseminated intravascular coagulation (DIC) and has a specific therapy (different from all other forms of AML).
As an additional example, evaluation of plasma cell proliferations relies heavily on cytomorphological and histological features in combination with immunohistochemical and in situ hybridization studies for clonality. However, even with these techniques, the appropriate classification (and prognostication) of the plasma cell neoplasm (PCN) must be based on close integration of the clinical, radiologic, and cytogenetic data in each case, as described again later in this chapter.
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DISORDERS OF ERYTHROID CELLS
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Group of erythroid disorders, due to nonneoplastic and neoplastic etiologies, resulting in anemia.
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Anemias represent a decrease in red cell mass or hemoglobin (Hgb) concentration, and often manifest with clinical features related to overall inadequate oxygen transport and/or volume depletion. The diverse underlying pathophysiologic mechanisms can be conceptually divided into three broad categories: decreased red cell production, increased destruction or turnover, and blood loss. In principle, the latter is most straightforward, but the source of bleeding is not always easily identified. Causes of decreased production, also referred to as hypoproliferative anemias, and increased destruction, can be related to a variety of neoplastic and nonneoplastic etiologies. Common causes of anemia are listed in Table 15-1. A thorough history and physical examination along with an appropriately directed laboratory investigation are paramount to properly identifying the cause and guiding therapy.
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Automated peripheral blood (PB) analyzers in clinical laboratories provide measurements of Hgb and hematocrit (HCT) concentration, or the percent of blood volume composed of red blood ...