[Small cell B-cell lymphomas: guidelines for differential diagnosis].

Area of Science:

• Hematology
• Oncology
• Immunology

Context:

• The classification of small B-cell lymphomas has evolved, with the World Health Organization (WHO) system replacing the R.E.A.L. (Revised European-American Lymphoma) classification.
• The WHO classification includes chronic lymphocytic leukemia (B-cell type), mantle cell lymphoma, follicular lymphoma, lymphoplasmacytic lymphoma/immunocytoma, hairy cell leukemia, and plasmacytoma.
• A key difference is the WHO's recognition of prolymphocytic leukemia as a distinct disease entity.

Purpose:

• To summarize the diagnostic and categorization characteristics of small B-cell lymphomas according to the latest WHO classification.
• To provide insights into the molecular biological and clinical features of these lymphomas.
• To highlight the differences between the WHO and R.E.A.L. classifications.

Summary:

• Small B-cell lymphomas originate from B cells at various differentiation stages, exhibiting features of their normal counterparts.
• Diagnosis typically involves assessing tumor cell growth patterns, cytology, immunophenotype, growth fraction, and reactive cell infiltrates.
• Molecular characteristics, particularly chromosomal translocations in follicular and mantle cell lymphomas, are crucial for understanding their pathogenesis.

Impact:

• The WHO classification discards the "umbrella grading" of lymphomas, emphasizing grading within specific disease entities due to heterogeneous progression.
• Mantle cell lymphomas, unlike other small B-cell lymphomas, may not have an indolent progression and are not considered "low-grade" tumors.
• Understanding these classifications aids in accurate diagnosis, prognosis, and treatment strategies for small B-cell lymphomas.