Extramedullary plasmacytoma with crystal inclusions arising from the palatal tonsil

A case of extramedullary plasmacytoma of the left palatal tonsil in a 51-year-old woman is reported. The histological features of the tumor are typical, except for the appearance of crystal inclusions in plasma cells, histiocytes and matrices. The developmental process and the nature of the crystal inclusions are discussed, based on electron-microscopic findings. The patient has been followed for one year post-operatively, and no clinical evidence of recurrence has been observed.