Lymphoplasmacytic lymphoma and other non-marginal zone lymphomas with plasmacytic differentiation.

Small B-cell lymphomas with plasmacytic differentiation frequently present diagnostic challenges. Session 3 of the 2009 Society for Hematopathology/European Association for Haematopathology Workshop focused on lymphoplasmacytic lymphoma (LPL). The submitted cases illustrated classic examples of bone marrow-based and nodal LPL and cases with atypical features, including unusual phenotypes or involvement of extranodal sites. Several cases showed varying degrees of overlap with marginal zone lymphoma, and, as acknowledged in the 2008 World Health Organization classification, a definitive distinction between these 2 possibilities cannot always be established. Session 6 of the workshop focused on other non-marginal zone lymphomas that may display plasmacytic differentiation. This session highlights the wide variety of neoplasms that enter into the differential diagnosis of small B-cell lymphomas with plasmacytic differentiation and demonstrates the use of clinical features and ancillary studies in establishing an appropriate diagnosis by 2008 World Health Organization criteria.