Diagnostic principles and new developments in primary cutaneous B-cell lymphomas.

The most common subtypes of primary cutaneous B-cell lymphomas are marginal zone B-cell lymphoma/immunocytoma, follicle center cell lymphoma, and large B-cell lymphoma of the leg. Precise classification (European Organization for Research and Treatment of Cancer (EORTC) scheme) can be achieved only after a complete synthesis of clinical, histopathological, immunophenotypic, and molecular features. It is extremely important to emphasize that primary cutaneous B-cell lymphomas differ significantly from their nodal counterparts and are frequently characterized by an excellent prognosis. Awareness of this special clinical behavior should prevent the application of unnecessarily aggressive treatment protocols. Future definitions of primary cutaneous B-cell lymphomas will be based on their etiology and pathogenesis and especially on their molecular features. Some important areas are presented where exciting findings have been detected.