Plasma cells can contain cytoplasmic vacuoles, granules, crystals and inclusions. These cytoplasmic structures may be observed both in reactive plasmacytosis (e.g. chronic infections) as well as plasma cell neoplasms. Russell bodies are multiple round cytoplasmic hyaline inclusions that are frequently seen in bone marrow aspirates in myeloma. They are composed of immunoglobulin molecules within vesicular structures derived from rough endoplasmic reticulum. Plasma cells containing them are sometimes referred to as Mott cells. Several Mott cells containing numerous Russell bodies can be seen in this image. Image courtesy of: Julie Feldstein, M.D., Director of Hematopathology, Professor of Pathology, Icahn School of Medicine at Mount Sinai, New York, NY, USA.