Tissue chimerism analysis after donor lymphocyte infusion: a case of deceptive evidence

A 31-year-old female with refractory extramedullary myeloid leukemia relapse underwent peripheral blood stem-cell transplantation from her HLA-identical brother. Hematopoietic recovery followed disappearance of the lesions. Studies three-months post-transplant showed complete chimerism (CC). Fourteen months after transplantation, the patient presented with an increasing number of extramedullary sites of biopsy-proven disease relapse (as nodular skin lesions). Bone marrow was in remission with maintenance of CC. However, tissue chimerism analysis showed full recipient-cell population. After one course of conventional dose chemotherapy followed by mobilized donor-lymphocyte infusions (DLI), a complete response was achieved. DLI continued monthly but she developed new skin lesions accompanied by multiple cervical masses. Bone marrow and tissue chimerism revealed both recipient and donor cell population. We conclude that tissue chimerism analysis after DLI may not accurately document the cell origin.