Chapter 10 Answers to self-check questions

10.1 These include pallor and lethargy, a consequence of anaemia; pharyngitis and recurrent infections, due to reduced production of normal effector white blood cells; easy bruising, caused by a reduction in the platelet count or the production of dysfunctional platelets; pyrexia, night sweats and flu-like symptoms, a consequence of increased inflammatory cytokines; bone pain, due to either myeloid expansion within the marrow or the activation of osteoclasts and bone remodelling in myeloma; lymphadenopathy, due to accumulation of malignant lymphocytes; splenomegaly and hepatomegaly, due to the accumulation of malignant haemopoietic cells or as a consequence of extramedullary haemopoiesis. Patients may also be asymptomatic.

10.2 The FBC can only provide quantitative data, i.e. the numbers or quantity of a particular type of cell or substance. Examples include the white cell count, red cell count, haemoglobin concentration, mean cell volume platelet count, mean cell haemoglobin concentration, neutrophils, eosinophils, basophils, lymphocytes, and monocytes.

10.3 They signify a myeloid population of cells. The presence of Auer rods excludes a lymphoid leukaemia. However, the absence of Auer rods does not exclude a myeloid malignancy.

10.4 The bone marrow aspirate contains cells with preserved morphology which makes the assessment of cellular structure and identification relatively straightforward. Aspirate samples should be taken from the iliac crest, or on occasion from the sternum; and these samples can be used for further investigation including cytogenetic analysis, immunophenotyping, or molecular techniques. An aspirate is processed by the haematology laboratory, with results ready in as little as an hour.

The bone marrow trephine is a core biopsy and so the architecture of the tissue is maintained. Although tissue cellularity can be determined from bone fragments in an aspirate, cellularity and cellular interactions can be much more accurately determined from the trephine. Areas of fibrosis and necrosis can be appreciated. A trephine biopsy required decalcification and sections to be processed and therefore needs to be processed by a histopathology laboratory with results available in one to two days.

10.5 40–70% is considered normocellular.

10.6 An increased bone marrow cellularity is called hypercellularity. The percentage of cells exceeds 70%. A reduced bone marrow cellularity (<40%) is called hypocellularity.

10.7 The process of malignant cells becoming deposited within the bone marrow from extramedullary sources.

10.8 The myeloperoxidase reaction produces a brown granular appearance to myeloid lineage cells. Early myeloblasts appear negative, but the intensity of the staining increases as the cells mature.

Sudan black B produces a black granular appearance comparable to the brown staining characteristics of myeloperoxidase.

Periodic acid–Schiff shows a pink/red reaction with all haemopoietic cells except for normal erythroid cells. Leukaemic erythroblasts show a positive reaction, and this helps in the identification of erythroleukaemia.

10.9 Immunophenotyping can help us identify particular cell lineages by quantifying the expression of CD markers on the cell surface or within the cytoplasm. Immunophenotyping can also help determine whether a population of cells is monoclonal or polyclonal, helping us determine whether we have a malignant or reactive population of cells.

10.10 Forward scatter represents the size of cells by measuring the amount of light passing through the cell of interest. Side scatter represents the internal complexity of cells by measuring light at 90º to the source. By correlating forward and side scatter using a scatter gram, the identity of cell populations based on size and complexity can be established.

10.11 Once a population of cells has been selected (or gated), any antibody reactions subsequent to the gating procedure will be applied to the selected population of cells. Gating enables the specific immunophenotype for a particular population of cells of be characterized.

10.12 They are important for the classification of certain haematological malignancies, for example acute promyelocytic leukaemia of chronic myeloid leukaemia; for the use of specific therapies, in certain cases—for example ATRA therapy in acute promyelocytic leukaemia and imatinib mesylate in chronic myeloid leukaemia; for assessing a patient’s prognosis; and for identifying clonal progression.

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