We describe a patient with a neoplasm derived from the histiocytic-monocytic lineage associated with t(2;5) detected by FISH. The patient presented with bone marrow involvement, no organomegaly and subsequently developed a leukaemic picture. The clinical course was aggressive and the patient died four months from diagnosis. Cell morphology, immunophenotype (CD30-, EMA-, Lisozyme+, cy CD68+ and CD45+) and DNA analysis showing germ-line configuration of the Ig/TCR chain genes ruled out the diagnosis of anaplastic large cell lymphoma (ALCL). This unusual case ilustrates that t(2;5) is not exclusive for ALCL but may be found in a few cases of rare neoplasms derived from the histiocytic-monocytic cells.