Light micrograph of a myelolipoma. A myelolipoma is a benign tumour which is composed of immature hematopoietic (blood forming) cells outside of the bone marrow. The cells making up a myelolipoma are identical to those normally found in the bone marrow. The large pink cells are megakaryocytes, precursors for platelets. The smaller cells throughout are a variety of precursor cells for red and white blood cells. The white circular structures are fat cells intermixed with the blood precursor cells. Haematoxylin and eosin stained tissue section. Magnification: 200x when printed at 10 cm.