Blastoid high-grade B-cell lymphoma initially presenting in bone marrow: a diagnostic challenge

Area of Science:

• Hematopathology
• Oncology
• Molecular Diagnostics

Background:

• The 2016 WHO classification includes high-grade B-cell lymphoma (HGBL), with blastoid-HGBL being poorly understood.
• Distinguishing blastoid-HGBL from B-acute lymphoblastic leukemia (B-ALL) in bone marrow presents diagnostic challenges.

Purpose of the Study:

• To identify distinct features differentiating blastoid-HGBL from B-ALL in bone marrow.
• To develop and validate a scoring system for classifying challenging blastoid lymphoid tumors.

Main Methods:

• Immunophenotyping, fluorescence in situ hybridization (FISH), and targeted next-generation sequencing (NGS) were used.
• 31 blastoid-HGBL cases were compared with 36 B-ALL cases.
• A six-feature scoring system was developed and validated on separate cohorts.

Main Results:

• Blastoid-HGBL cases showed increased CD20, CD38, CD45, BCL-6, and MYC expression, and decreased CD10 and TdT expression compared to B-ALL.
• MYC rearrangement, complex karyotype, and TP53 mutation were more frequent in blastoid-HGBL.
• The developed scoring system achieved 100% sensitivity and 94% specificity in distinguishing the two entities.

Conclusions:

• Blastoid-HGBL exhibits unique immunophenotypic, cytogenetic, and molecular characteristics compared to B-ALL.
• The proposed scoring system aids in the classification of difficult-to-diagnose blastoid lymphoid tumors presenting in bone marrow.