Clonal Immunoglobulin Gene Rearrangements and Normal T-Cell Receptor, bcl-2, and c-myc Genes in Primary Cutaneous B-Cell Lymphomas1

Fourteen cases of primary cutaneous B-cell lymphomas were investi gated at the immunohistochemical and molecular level to further char acterise this newly defined entity. Neoplastic cells from all cases, phenotypcd with a panel of monoclonal antibodies, were positive for 111.ADR, f jr the B-cell markers CD19, CD22, but not CD23 (except one case), and negative for the T-cell marker CD2. Monoclonal immunoglobulin li|;ht chains were demonstrated in six cases. The reactivity with the Ki-67 monoclonal antibody indicated that the neoplastic cells are proliferatini;. In five biopsies the presence of dendritic cells infiltrating the neoplsstic areas was revealed using the monoclonal antibody Kim4b. By Soul hern blot analysis, clonal rearrangement of the immunoglobulin heavy chain gene (involving one or both alÃ-eles)was shown in 12 of 14 cases and of the light chain genes in 13 cases. The bcl-2 oncogene, normally involved in nodal follicular lymphomas, was in germ-line con figurai ion. The c-myc and the ,( and •¿ > chain genes of the T-cell receptor were nlso in the germ-line configuration. None of the cases presented Epstein-Barr virus sequences. These data indicate that primary cutaneous lymphomas of B-cell origin share morphological and phenotypic similarities with the nodal B-cell lymphomas of follicular histotype, are proliferating, and express in 45% of cases clear monoclonal immunoglobulin light chain; the molecular analysis confirms the B-cell derivation and the monoclonal nature of this neoplasia; it also shows that neither bcl-2 nor c-myc oncogenes are involved and that no inappropriate rearrangements of the T-cell receptor genes ire found in this lymphoma.