Acute lymphocytic leukemia with microblastosis and near haploidy (26 chromosomes): a case report.

A three-year-old acute lymphocytic leukemia (ALL) patient had a modal chromosome count of 26 in her bone marrow metaphases. The leukemia was "common" ALL by cytochemical and immunologic studies. Five other cases had been reported previously, and all have had a near haploidy varying from 26 to 32 chromosomes. Disomy of chromosomes 18 and 21 is a consistent feature of this disease. Severe hypodiploidy correlates with microblastosis requiring morphologic separation from non-neoplastic small lymphocytes.