Primary cerebral diffuse large B-cell lymphoma relapsed solely in the skin with the same clonal origin.

Diffuse large B-cell lymphoma is the most common type of primary central nervous system (CNS) lymphoma(PCNSL) with poor prognosis. Relapse occurs early and most commonly in CNS, whereas systemic relapse solely in skin is exceptional. We presented a unique case of PCNSL in an 82-year-old man with 2 consecutive skin relapses without concomitant local failure or other systemic involvement. The lymphoma cells of all 3 specimens were of the same histology and immunophenotype with expression of CD20, IgM, bcl-2, bcl-6, and MUM1 but not CD3, CD10, CD30, IgD, cyclin D1,or cutaneous lymphocyte-associated antigen. The skin tumors were in the dermis and subcutis with a spared grenz zone. The brain and skin tumors demonstrated the same clonal origin by B-cell clonality study followed by cloning and sequencing. To our knowledge, this is the first case of PCNSL relapsed solely in the skin with proven clonal identity.