Bi-clonal, multifocal primary cutaneous marginal zone B-cell lymphoma: report of a case and review of the literature.

Bi-clonality is a rare phenomenon seen in approximately 5% of chronic B-cell lymphoproliferative disorders. Both true bi-clonality and somatic hypermutation resulting in intraclonal evolution have been described. We present the case of a 37-year-old female who developed extranodal marginal zone B-cell lymphoma with immunohistochemical studies showing monotypic immunostaining of plasma cells for immunoglobulin lambda light chain on her right arm in 2008. Three years later, she developed a second focus of extranodal marginal zone B-cell lymphoma on her left arm, but immunohistochemical studies demonstrated monotypic immunostaining of plasma cells for immunoglobulin kappa light chain confirmed after repeat analysis. Evaluation for systemic lymphoma with laboratory and imaging studies was negative. Together, the findings were consistent with bi-clonal, multifocal extranodal primary cutaneous marginal zone B-cell lymphoma. We present this case to highlight a rare phenomenon within primary cutaneous marginal zone lymphomas.