Deletion of the long arm of chromosome 20 (del 20q) has been observed in patients with myelodysplastic syndrome (MDS) or myeloid malignancies. We experienced an MDS female case of del 20q accompanied by clusters of plasmacytic cells in bone marrow. Her bone marrow cells showed morphological abnormalities in three lineages and the chromosomal abnormality of 46, XX, del (20) (q11.2q13.3). Although the percentage of plasma cells was low in free cells, such cells showed nuclear abnormalities. In bone marrow clots, we also observed clusters of anti-CD38 and anti-CD138 antibody-positive cells. According to the FAB or WHO classification, the diagnosis was unclear. Therefore, we were obliged to term this case as MDS with plasma cell dysplasia. This patient was considered to be a rare case of MDS related to abnormalities in myeloid and B-lymphoid cells.

T-cell Pro-Lymphocytic Leukemia (T-PLL) is a rare disease caused by malignancy of mature post-thymic T-cell. Myelodysplastic Syndrome (MDS) is caused by abnormal differentiation of myeloid lineage cells resulting in myeloid leukemia. Both of these hematological disorders are frequently diagnosed in elderly persons. Myeloid lineage is believed to be situated at the position far from lymphoid one as it is regarded on a tree diagram about the blood cell maturation. We reported herein a rare case of T-PLL accompanied by plural M-proteins with MDS a nonagenarian. The 96 years old patient was admitted to our hospital because of lymphocytosis and abnormal lymphocytes. From the bone marrow aspirate, biopsy and hematological findings, abnormalities were observed in cells of three different lineages, namely, (i) neutrophils with hypersegmented-nuclei (ii) erythroblasts with nuclear division, large platelets and megakaryoblastic cells, and (iii) reticulum cells with phagocytosed iron in their cytoplasm. Lymphocytes showed CD3 (+), CD4 (±), CD5 (+), CD8 (+), CD10 (+), CD56 (-) and CD57 (-). Mast cells and large lymphocytic cells with nuclear pockets were also seen. Anti-HTLV-1 antibody was negative. Soluble IL-2 receptor was significantly elevated to 7910 U/ml. Both IgGλ and IgGκM-protein were detected. No Bence-Jones protein was detected in the urine. Chromosomal abnormality of 45 (X, 0) or loss of Y chromosome was also demonstrated. Due to his high age, it was difficult to classify his condition according to the conventional classification. Thus, what we had experienced is truly a rare case that coincidentally showed T-PLL and MDS with plural M-proteins.