title: Differentiation of monoclonal B lymphocytosis of undetermined significance (MLUS) and chronic lymphocytic leukemia (CLL) with weak CD5 expression from CD5(-) CLL.
abstract: Chronic lymphocytic leukemia (CLL) is recognized as a unique lymphoproliferative disorder of CD5(+) B cells. However, many published series of CLL included a subgroup of CD5(-) cases. CD5(-) B cell CLL is a topic of controversy and its nature and true incidence remain unclear. We in this study performed a retrospective analysis of a total of 128 consecutive patients with a diagnosis of CLL and available immunophenotypic record. Of these, 14 cases were previously considered CD5(-) CLL. From a further analysis of clinical, hematological and immunophenotypic results, we have reclassified seven of the patients as having weak or dim expression of CD5 and four patients as being monoclonal B lymphocytosis of undetermined significance (MLUS). The remaining three cases had clinical and morphological features consistent with prolymphocytic leukemia (PLL) or mixed CLL/PLL. Our results suggest that the CD5(-) phenotype probably does not qualify for CLL. Previous CD5(-) CLL may include false negatives due to heterogeneity of the intensity of CD5 expression, CD5(-) MLUS and variant CLL; the latter likely represents CLL in transformation. All the patients with MLUS were found to have a mild and non-progressing lymphocytosis with CD5(-) phenotype. These features may be used to differentiate them from CLL.
authors.affiliation: Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, University of Toronto, Ontario, Canada. cwang@mtsinai.on.ca
authors.forename: Chen
authors.initials: C
authors.lastname: Wang
authors.forename: Dominick
authors.initials: D
authors.lastname: Amato
authors.forename: Rola
authors.initials: R
authors.lastname: Rabah
authors.forename: Jianing
authors.initials: J
authors.lastname: Zheng
authors.forename: Bernard
authors.initials: B
authors.lastname: Fernandes
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001402:B-Lymphocytes / Q000276:immunology / Q000473:pathology; D018956:CD5 Antigens / Q000032:analysis*; D002999:Clone Cells / Q000276:immunology / Q000473:pathology; D003937:Diagnosis, Differential; D003951:Diagnostic Errors; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D016130:Immunophenotyping; D015448:Leukemia, B-Cell / Q000175:diagnosis*; D015451:Leukemia, Lymphocytic, Chronic, B-Cell / Q000175:diagnosis* / Q000276:immunology*; D008218:Lymphocytosis / Q000175:diagnosis*; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies
chemical_list: D018956:CD5 Antigens