[Diagnosis of cutaneous B-cell lymphomas]

Skin is the second most common site of extranodal lymphoma. The significance of cutaneous B-cell lymphomas has been underestimated due to the lack of monoclonal antibodies and molecular genetics in former years. Cutaneous B-cell lymphomas represent a heterogeneous group of entities which show variation in histology, immunophenotype and in prognosis. The most common entities presenting in skin are follicular lymphomas, marginal zone B-cell lymphomas, and diffuse large B-cell lymphomas. The majority of primary cutaneous B-cell lymphomas have an excellent prognosis. Whereas in B-cell lymphomas with secondary spread to the skin the clinical course is dependent on the prognosis of the primary lymphoma. It is evident that primary cutaneous lymphomas are distinct from nodal lymphomas and not extranodal manifestations of their lymph-node-based counterparts. In the current review the morphologic spectrum of cutaneous B-cell lymphomas comprising primary and secondary cutaneous B-cell lymphomas is discussed according to the WHO classification scheme.