The lack of the normal distribution of these B cells is one basis for demonstrating clonality, the key element for establishing a diagnosis of any B cell malignancy (B cell non-Hodgkin lymphoma).The Matutess CLL score allows the identification of a homogeneous subgroup of classical CLL, that differs from atypical/mixed CLL for the five markers expression (CD5, CD23, FMC7, CD22, and immunoglobulin light chain)
Matutess CLL scoring system is very helpful for the differential diagnosis between classical CLL and the other B cell chronic lymphoproliferative disorders, but not for the immunological distinction between mixed/atypical CLL and mantle cell lymphoma (MCL malignant B cells). Discrimination between CLL and MCL can be improved by adding non-routine markers such as CD54 and CD200. Among routine markers, the most discriminating feature is the CD20/CD23 mean fluorescence intensity ratio. In contrast, FMC7 expression can surprisingly be misleading for borderline cases. Clinical staging
Staging, determining the extent of the disease, is done with the Rai staging system or the Binet classification (see details) and is based primarily on the presence of a low platelet or red cell count. Early-stage disease does not need to be treated. CLL and SLL are considered the same underlying disease, just with different appearances.
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.