Plasma cells are amazing! Their appearance reflects an extraordinary commitment to antibody production: the eccentric nucleus, the abundant cytoplasm filled with rough endoplasmic reticulum, the pale Golgi hof. Features we learn early in training become more interesting as we come to understand what they represent. Some plasma cells persist for decades, producing antibodies against infections we have long forgotten. I find that remarkable. Part of our immunologic history is maintained by these cells, quietly at work in the marrow. In neoplasia, they may retain that familiar appearance while producing a protein capable of causing profound injury. A seemingly mature plasma cell can belong to a clone whose antibodies damage the kidneys, deposit in tissues, or increase blood viscosity. Its appearance alone tells us surprisingly little about the harm it can cause. (Images of plasma cell myeloma and rouleaux) #Hematopathology #Pathology #hemepath #mmsm