CD5- small B-cell leukemias are rarely classifiable as chronic lymphocytic leukemia

Area of Science:

• Hematology
• Immunophenotyping
• Oncology

Background:

• CD5 antigen expression is a key diagnostic marker for B-cell chronic lymphocytic leukemia (B-CLL).
• However, some B-CLL cases lack CD5 expression, complicating diagnosis.
• Understanding CD5-negative B-cell lymphoproliferative disorders is crucial for accurate classification.

Purpose of the Study:

• To investigate the spectrum of CD5-negative B-cell lymphoproliferative disorders.
• To reassess the prevalence of CD5-negative B-cell chronic lymphocytic leukemia (B-CLL).
• To differentiate CD5-negative B-cell leukemias from other non-Hodgkin lymphomas.

Main Methods:

• Immunophenotyping of 192 clonal, small lymphocytic, B-cell disorders.
• Detailed analysis of 41 CD5-negative cases.
• Correlation of immunophenotypic findings with pathology and clinical data.

Main Results:

• Only 3 out of 41 CD5-negative cases were classified as B-CLL, exhibiting atypical features.
• The majority of CD5-negative cases were diagnosed as other B-cell lymphomas (e.g., hairy cell leukemia, SMZL, follicular lymphoma).
• Eight cases remained unclassified, with some showing features suggestive of splenic marginal zone lymphoma (SMZL).

Conclusions:

• CD5-negative lymphoproliferative disorders involving peripheral blood or bone marrow are seldom B-CLL.
• Accurate classification of these disorders often leads to a diagnosis of non-Hodgkin lymphoma in its leukemia phase.
• Distinguishing CD5-negative B-cell neoplasms is essential for appropriate patient management and treatment strategies.