The electron microscopic study of an extramedullary plasmacytoma of the pharynx was performed and the results were as follows: plasma cells. 2) The tumor cells had a mature-appearing , well-organized cytoplasm with abundant rough endoplasmic reticulum. 3) In contrast to the cytoplasm, cells had immature nuclei with very little chromatin aggregation or with scattered small aggregations of chromatin. Nucleoli were frequent, and in some cells were prominent. 4) Tumor cells demonstrated

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... plasmic asynchrony with cytoplasms disproportionately mature in comparison to the degree of nuclear differentiation. The degree of nuclear/cytoplasmic asynchrony was compatible with moderate asynchrony proposed by Graham and Bernier. 5) The phagocytosis of erythrocyte by the neoplastic plasma cell was observed. We reviewed the literature on the ultrastructural study of extramedullary plasmacytoma from the viewpoint of nuclear/cytoplasmic asynchrony. The correlation between ultrastructural features of the tumor cells and the clinical course of the disease was discussed.