In the tissue sections of axillary lymph nodes surgically removed from a case of malignant lymphoma (non-Hodgkin's, diffuse, large cell type), many large cells were observed to contain lymphoma cells in their cytoplasm. From the findings of light microscopy in serial sections and electron microscopy, this phenomenon was confirmed to be "emperipolesis." By immunohistochemistry, the large cells that contained lymphoma cells possessed most of the monocyte/macrophage markers, whereas the lymphoma cells revealed some B-cell markers, suggesting that they were of germinal center cell origin. In a survey of the literature, we found no report describing emperipolesis in the tissue sections of malignant lymphoma. Although the precise mechanisms and biological significance of emperipolesis in the present case are not fully understood, the existence of some interactions between macrophages and lymphoma cells is suggested.