In CLL, the lymphocytes are all genetically identical since they are derived from the same B cell lineage, expressing common B-cell markers CD19 and CD20, with abnormal expression of surface markers CD5 and CD23. These B cells resemble normal lymphocytes under the microscope, although slightly smaller, and are fragile when smeared onto a glass slide, giving rise to many broken cells, which are called "smudge" or "smear" cells and can indicate the presence of the disease. Smudge cells are due to cancer cells lacking in vimentin, a type of cytoskeleton proteins which is a structural component in a cell which maintains the cells internal shape and mechanical resilience). : 1899

Surface markers
The atypical molecular pattern on the surface of the cell includes the coexpression of cell surface markers clusters of differentiation 5 (CD5) and 23. In addition, all the CLL cells within one individual are clonal, that is, genetically identical. In practice, this is inferred by the detection of only one of the mutually exclusive antibody light chains, kappa or lambda, on the entire population of the abnormal B cells. Normal B lymphocytes consist of a stew of different antibody-producing cells, resulting in a mixture of both kappa- and lambda-expressing cells.
See also
Monoclonal B-cell lymphocytosis
Virtual karyotype
B-cell CLL/lymphoma

References
External links
Chronic Lymphocytic Leukemia Archived 2008-12-21 at the Wayback Machine at American Cancer Society
General information about CLL Archived 2004-10-19 at the Wayback Machine from the US National Cancer Institute
Cancer.Net: Chronic Lymphocytic Leukemia