Molecular diagnosis of skin relapse in acute lymphoblastic leukemia.

Despite improved survival in childhood acute lymphoblastic leukemia (ALL), its recurrence and the recognition of extramedullary dissemination continue to be crucial issues in the management of affected patients. We report the case of a boy with ALL who presented with two skin nodules during maintenance therapy. As histological examination of the routinely stained sections and the study of the immunophenotype of the skin biopsy were not conclusive, molecular analysis was carried out. By means of the heteroduplex analysis of the amplified T cell receptor (TCR) gene products we assessed the clonality of the skin lymphoid infiltrate and showed the same pattern of TCR gamma recombination of the bone marrow at diagnosis. The patient was treated with allogeneic bone marrow transplantation and survives disease-free after 3 years. Since cutaneous relapse in ALL occurs rarely, molecular analysis can be helpful and conclusive in defining the nature of a skin infiltrate.