Bone marrow is hypo-, normo- or hypercellular with normal or reactively changed hematopoiesis depending on the offending agent. Small granulomas consisting of epithelioid histiocytes are also dispersed throughout the marrow. Langhans-type giant multinucleated cells may also occur. Granulomas sometimes blend or even necrotize in the centre. Sometimes, peripheral lymphoplasmacytic cellulization is present.