Normal And Malignant Plasma Cells

Plasma cells are part of the normal cell population of the bone marrow. They comprise approximately 1% of the nucleated cells of normal marrow aspirates, and are equally distributed throughout the red marrow. Bone marrow findings of increased plasma cells, characteristic of myeloma, must always be taken together with other features before definite conclusions can be drawn, as high plasma cell numbers are seen in some reactive states, especially in HIV infection, autoimmune states, and liver disease. Aggregations of normal plasma cells usually occur in a perivascular distribution, with fewer than four or six cells clumped together. Normal plasma cells are of two major morphologic types. The classical "Marschalko" plasma cells are the predominant plasma cells in normal marrow. Such cells have abundant basophilic cytoplasm, paranuclear hof, and are usually devoid of nucleoli. The second appearance is of the lymphoplasmacytoid plasma cells, which are usually IgM secreting and are the predominant cells in Waldenstrom's macroglobu-linemia. These cells are smaller than "Marschalko" plasma cells, with less eccentricity of the nucleus, and are more dispersed in the bone marrow without perivascular cuffing. Malignant plasma cells can be differentiated by aggregation along endosteal surfaces, large clumps, and the presence of nucleated plas-mablasts or proplasmablasts. Binucleated plasma cells are occasionally seen in normal reactive marrow, and do not per se define malignancy. Electron microscopic appearances of normal plasma cells reveal peripheral chromatin condensation in an eccentric nucleus with well-developed paranuclear Golgi apparatus and cyto-plasmic endoplasmic reticulum. Normal plasma cells have an even distribution of kappa and lambda staining, whereas malignant clones are light-chain restricted. Morphologic abnormalities, such as crystal formation, Russell bodies, and "flame" cells are not usually seen in normal marrows, but are by no means pathognomonic of malignancy, as they can occasionally be seen in reactive states.

0 0

Post a comment