Therapy-related acute lymphoblastic leukemia with t(4;11)(q21;q23) masqueraded as marrow lymphocytosis in a patient with breast cancer.

Therapy-related acute leukemia develops in patients after chemotherapy and/or radiotherapy for a prior cancer, and most cases are acute myeloid leukemia with a much lower frequency of acute lymphoblastic leukemia (ALL). One unique feature of these therapy-related ALL (t-ALL) is an increased incidence of chromosome band 11q23 aberrations as compared with de novo ALL. In adult female patients, breast cancer is the most common primary cancer.