You have not mentioned that which organ was transplanted in you? Because incidence of PTLD and its reversion also depends upon the organ transplanted. The PTLD is type of B cells lymphoma which occur in the patients of organ transplant and are on immunosuppressent medicines. The person after transplant take immunospressant medicine and a virus called, Epstein Barr causes infection so the proliferation of B cells lymphocytes become uncontrolled. The PTLD can be treated by stopping immunospressant and taking antiviral medicines. In some patients, it leads to non-Hodgkin's lymphoma which is dangerous. So, wait for the doctor and see what treatment he starts.