The heavy chain gene is germline, but shows a pattern of faint bands indicating a polyclonal B-cell population. The Epstein-Barr virus probe demonstrates a strong clonal band, and two additional weak bands.
The EBV study demonstrates a clonal cell population characteristic of PTLD. The weaker bands probably represent rearrangements of the episomal EBV-DNA within this clone, but might instead indicate additional minor clonal populations. The lack of heavy chain gene rearrangement is observed in several categories of PTLD. Possible explanations include:
Despite the absence of a useful heavy chain marker, the EBV probe provides a sensitive test for detecting dissemination or recurrence in this patient. Ordinary Hodgkin's Disease frequently shows a weak clonal EBV band as is illustrated next to the patient sample. Hodgkin's Disease, like the present case, frequently does not show clonal immunoglobulin heavy chain gene rearrangment.
Dr. Nalesnik and I have reviewed the case and we believe that this patient has a variant form of PTLD that resembles Hodgkin's disease. We have recently reported a similar case*. That a PTLD might resemble Hodgkin's disease is not surprising, since the latter is also frequently associated with EBV, but in non-immunosuppressed patients. This tumor could also be diagnosed as the "polymorphic immunoblastic sarcoma" variant of PTLD, because of the presence of very large cells mixed with smaller cells.
*Nalesnik, M.A., Randhawa, P., Demetris, A.J., Casavilla, A., Fung, J.J., and Locker, J. (1993) Lymphoma resembling Hodgkin's disease following post-transplant lymphoproliferative disorder (PTLD) in a liver transplant recipient. Cancer 72(9):2568-2573.
Contributed by Joseph Locker, MD, PhD