Erythroids Information and Courses from MediaLab, Inc.
These are the MediaLab courses that cover Erythroids and links to relevant pages within the course.
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|Rules for Bone Marrow Differentials, continued|
Bone marrow smears can be very cellular and it can be difficult to keep track of where you are on the smear while keeping your correct hand position on the keyboard . Having a good strategy to use when counting cells and performing differentials can make this less difficult. On peripheral blood differentials, it is easy to observe and count each cell individually as the stage is moved to bring the next field into view. However, with bone marrows, the total number of keys that need to be used on the differential counter is greater than the number that need to be used with a peripheral blood smear and the number of cells per field is also increased dramatically, making it easy to lose track of the cells on the smear or one's hand/keyboard placement. It can be simpler and less stressful to work on the quadrant system. There are two different ways to do this: Divide the field into quadrants. Count the individual cells in each quadrant separately. This decreases the number of cells into more manageable bites. However, you still have the increased number of cell types to deal with and possible keyboard frame-shifts. Divide your keyboard into quadrants. Search your field for a limited number of cell types and tally all you see before moving on to the next grouping of cell types. Once you tally all your groups then move on to the next field (e.g., lymphocytes, monocytes, macrophages, eosinophils, basophils, plasma cells, erythroids, segmented neutrophils, bands, etc). You can make these small groupings for any cells as long as you cover the entire list of cell types that your laboratory reports in its bone marrow differential protocol. Remember that blasts are identified by cell type and there will usually be a separate key for pronormoblasts, myeloblasts, lymphoblasts, and possibly monoblasts and plasmablasts. It is possible to combine both methods, using the keyboard quadrant technique with a restricted portion of the total microscope field. This is useful when you are getting close to your total tally and do not want to alter the balance by only counting one cell type for the last few cells.
Lymphocytes mature in the lymph nodes rather than in the bone marrow and therefore are not routinely assessed when deciding if a marrow has "trilinear" (myeloid, erythroid, megkaryocytic) maturation. However, they are normally present in the bone marrow and, when clustered in a lymphoid follicle, can be very prominent. Since lymphocytes mature in the lymph nodes, they will appear identical to peripheral blood lymphocytes when viewed in the bone marrow. They will have the same range of variation in size and cytoplasm and will demonstrate the same types of viral transformations noted in the peripheral blood. Viral/atypical lymphocytes are combined together with normal lymphocytes in a bone marrow differential count and not placed into their own category, as they are in a peripheral blood differential. However, the hematopathologist may include this information in the interpretation, if these changes are noted.Lymphocytes can be found scattered throughout the bone marrow and must be distinguished from early erythroid precursors, which they can closely resemble. Lymphocytes are frequently found in and around early NRBC clusters. In the top image on the right, notice the medium-sized lymphocyte (red arrow) next to the two basophilic normoblasts (blue arrow). The color and texture of the scant lymphoid cytoplasm is almost identical to the NRBC, which can be a bit confusing. However, observe the differences in the nuclei between the two cell types. The lymphocyte has a less distinct chromatin clumping pattern than the basophilic normoblasts and the lymphocyte does not have any "nuclear pores." Also, the lymphocyte has an irregularly-shaped nucleus that is hugging the cytoplasmic border, while the NRBC has a round and regular, centrally-placed nucleus. Identify the three lymphocytes circling the NRBCs in the second image (see red arrows). Notice the chromatin of the lymphocytes; the lymphoid smudgy/clumpy pattern is certainly not as dense and clumped as what is noted in the NRBCs. This nuclear difference becomes more pronounced as the erythroids mature. The cytoplasmic differences should be more apparent as well, since lymphocytes will never produce hemoglobin.