Bone marrow nonneoplastic
Benign changes
Systemic polyclonal B immunoblastic proliferation
Last author update: 1 March 2014
Last staff update: 7 December 2023
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PubMed Search: Systemic polyclonal B immunoblastic proliferation
Table of Contents
Definition / general | Laboratory | Prognosis | Case reports | Treatment | Microscopic (histologic) description | Cytology description | Peripheral smear description | Positive stains | Negative stains | Flow cytometry description | Molecular / cytogenetics description | Differential diagnosisCite this page: Zhao X. Systemic polyclonal B immunoblastic proliferation. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/bonemarrowsystemicpolyclonal.html. Accessed April 20th, 2024.
Definition / general
- See also lymphoid aggregates, plasmacytosis and polymorphous reactive lymphoid hyperplasia
- A florid, systemic polyclonal proliferation of B immunoblasts accompanied by polyclonal hypergammaglobulinemia
- Rare, reactive, often associated with an acute immune disorder
- Involves peripheral blood, bone marrow, lymph nodes; often liver and spleen
- In peripheral blood, usually elevated WBC count with high percentage of B immunoblasts
- In middle aged / elderly, may be related to EBV (Pathol Res Pract 2006;202:609) or Pseudomonas (Am J Clin Pathol 1992;98:222)
- > 10% circulating lymphocytes with immunoblastic morphologic features may be seen in hantavirus cardiopulmonary syndrome (Am J Clin Pathol 2001;116:665)
- May mimic a neoplastic process
Laboratory
- CBC: usually leukocytosis with absolute lymphocytosis; neutrophilia with left shift may be present
- Anemia and thrombocytopenia are almost always present
- Positive antiglobulin test, as the anemia is frequently immune mediated
- Hypergammaglobulinemia, polyclonal per immunofixation electrophoresis (IFE)
Prognosis
- Rapid regression of disease process may occur
- Most patients who recover do not relapse but patients may die in acute phase (Cancer 1988;61:1350)
Case reports
- 43 year old woman (J Forensic Sci 2001;46:156)
- With marked peripheral blood and bone marrow plasmacytosis (Am J Clin Pathol 1992;98:222)
Treatment
- Supportive care and treatment tailored to associated immune disorder
- Variable response to treatment; many respond to steroids while others require chemotherapy (vincristine and cyclophosphamide) (Cancer 1988;61:1350)
Microscopic (histologic) description
- Hypercellular marrow with extensive infiltration resembling lymphoma or plasmablastic myeloma, due to lymphocytes, immunoblasts, plasma cells, intermediate forms
- Focal lymphocytic aggregates are characteristically present, varying from inconspicuous to large
- Similar infiltrate may be seen in lymph nodes with complete effacement of nodal architecture
- Immunohistochemistry is critical to demonstrate polytypic nature of process
Cytology description
- Bone marrow aspirate smear shows numerous lymphocytes, immunoblasts, plasma cells
- Prominent immunoblastic cytomorphology with intensely basophilic cytoplasm, relatively coarse chromatin pattern, distinct central nucleoli
- Frequently, evidence of maturation to plasma cells can be seen
Peripheral smear description
- Elevated WBC count with absolute lymphocytosis including reactive lymphocytes, immunoblasts, plasma cells
- Neutrophilia with left shift may be present
- Anemia and thrombocytopenia are almost always present
Positive stains
- B cell markers and plasma cell markers in appropriate cellular components
- Plasma cells and immunoblasts are polytypic for immunoglobulin light chain staining pattern
Negative stains
- No aberrant antigen expression
- No light chain restriction
Flow cytometry description
- Polytypic B cells per surface (B cells) or cytoplasmic (plasma cells) light chain expression
- No aberrant antigen loss or expression
Molecular / cytogenetics description
- PCR reveals germline immunoglobulin and T cell receptor genes in polyclonal rearrangement pattern
- Rarely, oligoclonal B and T cell populations are demonstrated by PCR
- Clonal cytogenetic abnormalities have been identified in a subset of patients, raising the possibility of a cryptic neoplastic proliferation
Differential diagnosis
- Non-Hodgkin lymphoma with immunoblastic morphologies and some plasma cell dyscrasias (plasmablastic myeloma) have monotypic light chain expression
