Extranodal Marginal Zone B Cell Lymphoma
Definition
- Neoplasm composed primarily of small B lymphocytes frequently with moderately abundant pale cytoplasm (monocytoid cells) and a predilection for involvement of mucosal sites
Alternate/Historical Names
- Maltoma
- Monocytoid lymphoma
- Immunoproliferative small intestinal disease (variant)
- IPSID (variant)
- Alpha heavy chain disease (variant)
- Mediterranean Lymphoma (variant)
Diagnostic Criteria
- Other than monocytoid cells, lymphoepithelial lesions, marginal zone involvement and follicular colonization, most of the findings are rather nonspecific for distinction from other small B lymphomas
- Small to medium sized cells
- Nuclei round or indented
- Clumped chromatin
- Cytoplasm inconspicuous to moderately abundant and pale (monocytoid)
- Plasmacytoid differentiation frequent
- Can be extensive, resembling plasmacytoma
- Many head and neck plasmacytomas may actually be marginal zone lymphomas
- May form lymphoepithelial lesions
- Infiltration of non-neoplastic epithelium by lymphoma cells
- Three or more lymphoid cells
- Destruction of epithelium
- Typically increased eosinophilia
- Relatively specific finding if present
- Infiltration of non-neoplastic epithelium by lymphoma cells
- May involve marginal zones of reactive follicles
- Cells in marginal zone frequently monocytoid
- Infiltrate usually extends from marginal zone into adjacent regions
- May become interfollicular
- May show follicular colonization
- Infiltration of germinal centers by lymphoma cells
- Typically large cells
- In spite of large cells, no worsening of prognosis
- Relatively specific finding if present
- Lacks specific markers of other small cell lymphomas
- Negative to infrequent for CD23, bcl1, CD5, CD10
- Positive for B lineage markers and bcl2
- No specific positive immunologic marker
- Immunologically, a diagnosis of exclusion
- Preferentially involves epithelial organs or sites
- Location not diagnostic as other lymphomas may involve the same sites
- Same histologic and immunologic findings in lymph node or spleen is designated nodal or splenic marginal zone lymphoma
- Transformation reported in 20% of cases
- Either at diagnosis or subsequently
- Usually large B cell lymphoma
- Hodgkin lymphoma has been rarely reported
- Immunoproliferative small intestinal disease variant produces only alpha heavy chains
Yasodha Natkunam MD PhD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting:: October 11, 2006
