Light green crystals in May-Grünwald and Giemsa-stained bone marrow macrophages in patients with myeloid leukaemia

A patient in a terminal stage of myelomocytic leukaemia had a number of elongated crystals in many bone marrow macrophages. The crystals were up to 20 micron long, showed a characteristic light green colour with May-Grünwald & Giemsa, but did not stain with Sudan Black B or PAS. Electron microscopy showed that many of the crystals had a rhomboid form, but failed to show periodicity with the magnification used. A search was made for similar light green crystalline inclusions in patients with different types of leukaemia. Identical inclusions were found in 2 out of 5 other cases of myelomonocytic leukaemia, and in 3 out of 5 cases of chronic myeloid leukaemia. In contrast, such inclusions were not found in any of 6 patients with acute lymphoblastic leukaemia, nor in 4 patients with chronic lymphocytic leukaemia.