A Highly Abnormal Clone in a Pediatric Patient with B-Lymphoblastic Leukemia.

We present a case of a 14-year-old male who presented with loss of appetite, nosebleeds, and fatigue. He visited the clinic, and bone marrow studies were suggested. Bone marrow, core biopsy and clot section showed hypercellularity (80-90%) with sheets of blasts with suspicion of precursor B acute lymphoblastic leukemia (B-ALL). Chromosome analysis of 20 trypsin-Giemsa banded metaphase spreads showed an abnormal male composite karyotype described as 45~47,XY,+1,add(1)(p13),add(1)(q10),add(7)(q36), add(12)(q24.1),der(12)(p13->q24.1::12p13.2->12p13.1::12q24.1->12qter),-13,-15,add(16)(p13.1),-17,+1~3 mar[cp17]/46,XY[3]. Fluorescence in situ hybridization (FISH) was performed, showing one diminished signal for ETV6 in 99% [198/200] of the nuclei examined with the ETV6/RUNX1 probe. ETV6 break-apart probe on interphase nuclei showed one fusion (normal) and one green signal (5'ETV6) in 92% [184/200] of the nuclei. Metaphase FISH with the ETV6 BA probe showed one fusion on the normal chromosome 12 and one green signal (5'ETV6) on the long arm of the derivative chromosome 12. Additionally, metaphase FISH showed a 1q25 signal (green) in one abnormal copy of chromosome 1 as well as 1p36 signal (orange) in the additional abnormal copy of chromosome 1, and a retinoblastoma (Rb) signal (13q14.2) on the derivative chromosome 7. In light of these studies, the karyotype was described as a highly complex karyotype associated with genomic instability and a poor prognosis.