Primary breast diffuse large B-cell lymphoma shows an activated B-cell-like phenotype

Area of Science:

• Hematology
• Oncology
• Immunohistochemistry

Background:

• Diffuse large B-cell lymphoma (DLBCL) is classified into germinal center B-cell-like (GCB-DLBCL) and activated B-cell-like (non-GCB-DLBCL) subtypes.
• Cell of origin determination, via microarray or immunostain algorithms, holds prognostic value in DLBCL.
• Primary breast DLBCL often presents with poor clinical outcomes, necessitating further stratification.

Purpose of the Study:

• To stratify primary breast DLBCL using established immunostain algorithms (Hans, Choi, Meyer).
• To elucidate the factors contributing to the poor clinical outcome in primary breast DLBCL.
• To analyze histopathologic and immunophenotypic features, including proliferative activity.

Main Methods:

• Retrospective study of 22 primary breast DLBCL cases diagnosed per WHO 2008 classification.
• Immunohistochemical analysis to determine cell of origin subtypes.
• Assessment of Ki-67 labeling index for proliferative activity and analysis of follow-up data.

Main Results:

• The majority of primary breast DLBCL cases were classified as activated B-cell-like subtypes (17/22, 16/22, 17/22 by different algorithms).
• A smaller proportion were classified as GCB-DLBCL subtypes (5/22, 6/22, 5/22 by different algorithms).
• Fourteen out of 22 cases exhibited high proliferative activity (≥40% Ki-67 labeling).

Conclusions:

• Primary breast DLBCL predominantly exhibits activated B-cell-like subtype characteristics.
• High proliferative activity is a common feature in these tumors.
• Activated B-cell-like subtype and high proliferative activity are likely significant factors contributing to the poor prognosis of primary breast DLBCL.