Primary B-cell lymphomas of the skin are defined as malignant B-cell proliferations pre-senting with cutaneous involvement alone and no evidence of extracutaneous manifestations over a period of at least six months when complete staging has been performed. The major subtypes are fol-licle center-cell lymphoma, marginal zone lymphoma and large B-cell lymphoma of the leg (EORTC classification 1997). Primary B-cell lymphomas of the skin differ significantly from nodal lymphomas especially with respect to their clinical behavior. Pseudolymphomas of the skin are inflammatory dis-eases that simulate malignant lymphomas either clinically, histopathologically, or both. Particular pseudolymphomas may mimic cutaneous B-cell lymphomas. The most important examples are: lym-phomatoid drug reactions, lymphocytoma (borrelia burgdorferi as causative agent), arthropod reac-tions, pseudolymphomas associated with vaccinations or tattoos and inflammatory pseudotumors. In recent years, new immunohistological and molecular techniques have added important criteria for the differentiation of cutaneous lymphomas from pseudolymphomas.