Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (341 page)

   Platelet count is decreased in advanced disease. Occasionally, there is an autoimmune component to thrombocytopenia (ITP). In these cases, the bone marrow reveals a normal number of megakaryocytes. If thrombocytopenia is solely immune in etiology, it does not indicate advanced disease.

   WBC count is increased, usually 50,000–250,000/μL, with >90% lymphocytes. Neutropenia indicates progressive disease, unless it is the result of therapy. Recently, an entity of monoclonal B lymphocytosis has been described, and it refers to monoclonal B lymphocytes in patients with absolute lymphocyte counts <5,000/μL. MBL is best detected by flow cytometric analysis of peripheral blood in the absence of a history of B-cell leukemia or another related lymphoproliferative disease. Some of these patients may eventually evolve into typical CLL and need to be followed closely.

   In stable CLL/SLL, the lymphocytes are small, with clumped chromatin, indistinct nucleoli, and scanty cytoplasm. Smudge cells are numerous; their presence suggests CLL/SLL even if the WBC count is not greatly elevated. Increasing numbers of lymphocytes (lymphocyte doubling time in <1 year) or increased percentage of prolymphocytes indicate progressive disease.

   
Bone marrow
: Bone marrow aspiration and biopsy are seldom required for diagnosis. Bone marrow biopsy may show a pattern of nodular, interstitial, combined nodular and interstitial, or diffuse infiltration by lymphocytes. Progressive replacement of erythroid, myeloid, and megakaryocytic series by lymphocytes takes place over time.

   
Lymph node biopsy
: The histopathologic findings in CLL and SLL are identical. The lymph nodes show diffusely effaced nodal architecture with pale areas corresponding to proliferation centers in a dark background of small cells. The cells in the proliferation are mostly small, noncleaved lymphocytes with condensed chromatin, round nuclei, and occasionally single small nucleoli. There is an admixture of prolymphocytes and paraimmunoblasts usually clustered in proliferation centers. The proliferation index is low.

   
Immunophenotype analysis, usually by flow cytometry, is a key component to the diagnosis of CLL
. A major criterion for the diagnosis of CLL is the demonstration of clonality of circulating B lymphocytes. Flow cytometry reveals the expression of B-cell–associated antigens CD19, CD20 (weak), CD22, CD23, CD43, CD79a, and CD11c (weak). Cyclin D1, CD10, FMC7, CD79b, and CD103 are negative; CD5, a T-cell–associated antigen, is
uniformly present on CLL/SLL cells.
Mantle cell lymphoma cells (Table
9-3
) are also positive for CD5. Staining for surface IgM/κ or IgM/λ (whichever represents the abnormal clone) is dim. Minimal residual disease assessment in posttherapy hematologic remission is determined by multicolor flow cytometry and compared with the initial pattern.

   
Cytogenetics
: Chromosomal abnormalities can be detected in most cases of CLL, particularly with the recent use of CpG-rich oligonucleotides as a mitogen in cell culture. Common abnormalities include trisomy 12, 11q22-23 (ATM) deletion, 13q14.3 deletion, 17p13 (TP53) deletion, and 6q21 deletion. Deletion of 13q is often cytogenetically cryptic and requires detection by FISH. The other deletions may also be cryptic and are typically included in a CLL FISH panel.

   
Prognostic markers

   The expression on leukemic cells of ZAP-70, CD38, and unmutated immunoglobulin heavy chain variable region is associated with aggressive disease. Because of lack of methodologic standardization, immunoglobulin mutation status assays are not recommended at this time.

   Cytogenetic studies segregate prognosis as follows (in order of decreasing survival): isolated deletion 13q14.3 (best survival), normal karyotypes, trisomy 12 (the prognostic value of trisomy 12 is not clear, but so far considered as being intermediate), 11q/ATM deletion, and 17p/p53 deletion (shortest survival).