Preponderant mitotic activity of nonleukemic cells plays an important role in failures to detect abnormal clone in childhood acute lymphoblastic leukemia.

At diagnosis, clonal chromosomal abnormalities are found in the bone marrow blasts in more than two thirds of children with acute lymphoblastic leukemia (ALL). Practically, however, failure to detect these abnormalities is frequent and usually attributed to poor marrow sampling, inadequate metaphases, and/or a preponderant mitotic activity among nonleukemic cells. The authors applied fluorescence in situ hybridization (FISH) techniques to re-examine 30 cases of karyotypically "normal" childhood ALL to explore the role of preponderant mitotic activities of nonleukemic cells in failures to detect clonal abnormalities.

Transient myeloproliferative disorder in a phenotypically normal infant with i(21q) mosaicism.

We report a case of transient myeloproliferative disorder (TMD) that occurred in a phenotypically normal infant with low level constitutional mosaicism of i(21q). To the best of our knowledge, this is the first documented case of TMD with constitutional i(21q) mosaicism.