Unusual type of TLS/FUS-ERG chimeric transcript in a pediatric acute myelocytic leukemia with 47,XX,+10,t(16;21)(p11;q22)

We report on a case of pediatric acute myelocytic leukemia showing 47,XX,+10,t(16;21)(p11;q22) that resulted in an unusual TLS/FUS-ERG chimeric transcript. The leukemic cells showed erythrophagocytosis, positive reactions for myeloperoxidase and Sudan black B stains, and negative reactions for periodic acid-Schiff and α-naphtyl butyrate esterase stains as well as expression of myeloid antigens. We also confirmed a very rare type of TLS/FUS-ERG chimeric transcript by fusion of the 5′ part of the TLS/FUS gene in chromosome 16p11 and the 3′ part of the ERG gene in chromosome 21q22 using reverse-transcriptase polymerase chain reaction and direct sequencing. After achieving a complete remission with two cycles of induction chemotherapy, the patient received an umbilical cord blood transplantation.