2005 Volume 15 Issue 2 Pages 7-14
We performed flow cytometric and ultrastructural studies of pure erythroid leukemia (M6b) with carbonic anhydrase I (CA I) expression. A total of fifteen patients (mean age 46 years, range 1 to 85 years) were examined. The initial diagnoses were chronic myeloid leukemia in two, myelodysplastic syndrome in nine including four cases of Down syndrome, pancytopenia or bicytopenia in three, and myelofibrosis in one. Flow-cytometrically, almost all tumor cells were positive for CD36. CD4 and CD7 (T-cell markers), as well as CD13 and CD33 (panmyeloid markers) were also expressed in more than 90% of cases. Blood type antigens were also positive in 8 of 10 cases. CD34, CD117 and HLA-DR (immature myeloid markers) were also expressed in approximately 80% of cases. Other positive myeloid markers were CD45RA (7/13, 54%), CD11b (5/12, 42%) and CD45RO (9/13, 69%). Blast cells were positive for CD41, 61, 42a and 42b (megakaryocytic markers) in 60% of cases, but CD235a (specific marker for erythroid cells) was expressed in 7 of 15 cases (47%). Electron microscopic studies of platelet peroxidase (PPO) reaction revealed that in five of fourteen cases a very small number of tumor cells showed positive reaction. In conclusion, to make diagnosis of M6b, investigation of erythroid markers are mandatory, because tumor cells of M6b showed variable antigens, such as CD4, 7, 13, 33, 34, 36, 41, 42b, 61, 117, HLA-DR and PPO. CD36 is suitable for screening erythroid lineage marker, and blood type antigens and CA I are specific antigens for M6b besides CD235a.