CD7, CD34-positive stem cell leukemia arising in agnogenic myeloid metaplasia.

Agnogenic myeloid metaplasia (AMM) is a chronic myeloproliferative disorder arising from a single hematopoietic cell. Approximately 5% of reported cases of AMM have terminated in leukemic crisis; however, the precise characteristics of the leukemic cells have rarely been reported. We report a case of AMM that occurred in a 42-year-old man and was complicated by leukemic transformation. The leukemic cells were morphologically lymphoblastoid cells with a negative reaction to peroxidase staining, and phenotypically characterized as CD7+, CD34+, HLA-DR+, CD4-, CD8-, CD10-, CD13-, and CD33-. Southern blot analysis revealed that T cell receptor-beta, gamma, and immunoglobulin heavy chain genes in leukemic cells were retained in germ-line configuration. These observations suggest that leukemic cells in our case involved early hematopoietic stem cells rather than those strictly committed to myeloid or lymphoid precursors. To our knowledge, this is the first report of stem cell leukemia arising in a patient with AMM.