Bone marrow trephine morphology and immunohistochemical findings in chronic myelomonocytic leukaemia.

Chronic myelomonocytic leukaemia (CMML) is a clonal disorder with myelodysplastic/myeloproliferative features. Its diagnosis is based on the presence of peripheral blood monocytosis and bone marrow aspirate findings, according to World Health Organization criteria. However, bone marrow trephine biopsy (BMTB) features characteristic of CMML have not been adequately investigated. We studied BMTB in 20 cases of CMML-1 and three cases of CMML-2 and compared with ten cases of polycythaemia vera, ten cases of chronic myeloid leukaemia (chronic phase) and ten cases of florid myeloid hyperplasia (MH). Furthermore, we evaluated the use of CD34, CD117 and CD68 (PGM-1) antibodies in diagnosis and subtyping of CMML and in differentiating from other categories. Hypercellularity, high myeloid:erythroid ratio, increased proportion of 'myelo/monocytic' cells often seen as clusters and/or nodules, absence of eosinophilia, and presence of abnormal localisation of immature precursors (ALIP) and dysmegakaryopoiesis can aid in the diagnosis of CMML in BMTB. CD68 (PGM-1) positive cells amounted to 20.7 +/- 6.1% cells among CMML trephines. The proportion of CD34(+) cells among cases of CMML-1 was </=5% and among CMML-2 was >/=10% cells in two of three cases and 5% in the other case. Morphological and immunohistochemical features of BMTB samples are extremely helpful in the diagnosis of CMML.