Localized extramedullary relapse after autologous hematopoietic stem cell transplantation in multiple myeloma.

Extramedullary plasmacytomas are rare manifestation of plasma cell malignancies. After hematopoietic stem cell transplantation HSCT, presentation of localized plasmacytoma with extramedullary growth is very unusual. We report a case of a 56-year-old woman with Dune-Salmon stage IIIA immunoglobulin A-kappa multiple myeloma, which presented 120 days after autologous HSCT with extramedullary plasmacytoma arising from a lymph node in supraclavicular region. The patient had no pretransplant-history related with extramedullary disease. There was no increase of plasma cells in bone marrow or monoclonal protein in urine or serum. Aspiration smears of lymph node revealed a population of plasmacytoid cells at various stages of maturation. The patient was successfully treated with local radiotherapy and has remained progression-free for more than 20 months.