Cell marker analysis of extranodal lymphoid infiltrates: to what extent does the determination of mono- or polyclonality resolve the diagnostic dilemma of malignant lymphoma v pseudolymphoma in an extranodal site?

Lymphoid cell marker analysis has provided objective immunologic criteria by which to distinguish between benign pseudolymphomas and malignant lymphomas occurring in extranodal sites and has improved our understanding of extranodal lymphoid proliferations, thereby substantially altering our perspective of these lesions. These studies have resulted in a dramatic reclassification of the majority of the extranodal small lymphocytic proliferations (previously designated pseudolymphomas by histopathologic criteria) as malignant lymphomas, based upon immunologic criteria. However, this redefinition has not truly resolved the diagnostic dilemma of the extranodal small lymphocytic proliferation, nor has it measurably improved our ability to accurately predict patient outcome. It appears that the majority of patients with a monoclonal B small lymphocytic lymphoma localized to a solitary extranodal site enjoy a benign clinical course and long survival with only minimal therapeutic intervention.