Extramedullary T lymphoblastic transformation of chronic myeloid leukaemia occurring after double allogeneic transplantation.

The clinical course of chronic myeloid leukaemia (CML) is characterised by a chronic phase followed by an acute phase or blast crisis. Lymphoid transformation accounts for 20-30% of such events, with the majority of cases being of B cell origin. Extramedullary transformation occurs in approximately 10% of cases. We report a case of T cell lymphoblastic transformation in CML presenting as an extramedullary mass after allogeneic stem cell transplant. This case supports the growing evidence that CML arises in the pluripotent stem cell.