[PAX5-positive plasma cell leukemia presenting as lymphocytosis]

Area of Science:

• Hematology
• Oncology
• Genetics

Background:

• Plasma cell leukemia (PCL) is an aggressive hematologic malignancy.
• PCL typically presents with distinct clinical and laboratory findings, but atypical presentations can occur.

Observation:

• An 82-year-old male presented with lymphocytosis, initially misdiagnosed.
• Flow cytometry revealed monoclonal CD38+, CD138+, cytoplasmic κ+, IgG-κ M-protein-expressing lymphocytes, confirming PCL.
• Cytogenetic analysis identified a t(9;14)(p13;q32) translocation with high PAX5 expression.

Findings:

• The patient succumbed to the disease despite bortezomib and dexamethasone treatment.
• PAX5 overexpression is implicated in the pathogenesis of PCL presenting as lymphocytosis.
• This presentation may represent a unique subgroup of PCL.

Implications:

• Accurate differential diagnosis is crucial for PCL presenting with lymphocytosis.
• Urgent, multidisciplinary intensive treatment is required for this aggressive condition.
• Further research into the role of PAX5 in PCL pathogenesis is warranted.