Tumour regression following stem cell infusion from daughter to microchimeric mother.

Fetal cells are known to persist in mothers for many years. We report a patient with poorly differentiated epithelial thymic carcinoma who had a large anterior mediastinal tumour, pericardial mass, left upper and right middle lobe tumour masses, and right liver mass. She received a single infusion of 10(10) stem cells from her 32-year-old daughter. Before the transfusion, she had had persistent chimeric cells from her daughter. The tumour regressed after stem cell infusion and has remained in regression for over 1 year. The daughter's cells were present at 330 days post infusion.