Granulocytic sarcoma in MLL-positive infant acute myelogenous leukemia - Fluorescence in situ hybridization study of childhood acute myelogenous leukemia for detecting MLL rearrangement

Granulocytic sarcoma is considered to be rare and its frequent occurrence i s associated with specific genetic changes such as t(8;21). To investigate an association between MLL (mixed lineage leukemia or myeloid-lymphoid leuk emia) rearrangement and granulocytic sarcoma, we applied fluorescence in si tu hybridization for detection of the 11q23/MLL rearrangements on the bone marrow cells of 40 patients with childhood acute myelogenous leukemia (AML) . Nine (22.5%) of 40 patients exhibited MLL rearrangements. Three (33.3%) o f these nine patients had granulocytic sarcoma and were younger than 12 mon ths of age. Of these three patients one presented as granulocytic sarcoma o f both testes with cerebrospinal fluid involvement, the second case present ed in the form of an abdominal mass, and the third as a periorbital granulo cytic sarcoma. On the other hand, no granulocytic sarcomas were found among MLL-negative patients. It is likely that MLL-positive infant AML may predi spose granulocytic sarcoma. Regarding the findings of our study and those o f other reports, we would guess that the incidence of granulocytic sarcoma in pediatric MLL-positive AML may be equal to or greater than the 18 to 24% described in AML with t(8;21). Further investigations designed to identify 11q23/MLL abnormalities of leukemic cells or extramedullary tumor may be h elpful for die precise diagnosis of granulocytic sarcoma.