Clinical Pathology: General Principles, Hematology & Coagulation, Immunology & Histocompatibility, Urinalysis, Body Fluids, Clinical Microscopy, Genetic Testing


A 63-year-old woman with hypertension and hyperlipidemia presents to her primary care physician for a routine checkup. She feels well and has well-controlled blood pressure and lipid levels; however, a complete blood cell count shows mild leukocytosis (white blood cell [WBC] count, 13.0 × 109/L; reference range, 3.54 to 9.06 × 109/L) with atypical lymphocytosis (60% neutrophils, 5% lymphocytes, 30% atypical lymphocytes, 3% monocytes, and 2% eosinophils; reference ranges, 40% to 70% neutrophils, 20% to 50% lymphocytes, 2% to 8% monocytes, 0% to 6% eosinophils, 1% to 2% basophils). Her physician chooses to send a sample for flow cytometry evaluation. Representative flow cytometry results are shown in Figures 1, 2, and 3. Use this scenario to answer the following four questions.

Which one of the following is the most appropriate diagnosis for this patient?

• Monoclonal B-cell lymphocytosis (MBL) is characterized by a clonal proliferation of atypical B cells with a similar phenotype to chronic lymphocytic leukemia (CLL)/small lymphocytic lymphoma (SLL) but with a lower absolute lymphocyte count (<5 × 109/L).

• CLL/SLL is a low-grade B-cell neoplasm.

• CLL/SLL is characterized by CD5+, CD23+, CD20 dim, mature B cells.

• The diagnosis of CLL requires an absolute lymphocyte count of at least 5 × 109/L for 3 months.

• The diagnosis of SLL requires infiltration of organs or lymph nodes with a neoplastic infiltrate.

• CLL/SLL can progress to classical Hodgkin lymphoma (CHL) or diffuse large B-cell lymphoma (DLBCL), but more classically undergoes Richter’s transformation to DLBCL.

• Several factors are associated with poor prognosis in CLL/SLL. These include: CD38 and ζ-chain (T-cell receptor)-associated kinase 70 (ZAP-70) expression, germline (unmutated) immunoglobulin heavy variable cluster (IGHV) gene, del11q22-23, del17p, and del7q.

• Isolated del13q14.3 and mutated IGHV gene are associated with a good prognosis in CLL/SLL.

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