<p>The French-American-British subtype acute myelomonocytic leukemia with abnormal eosinophils (FAB AML M4Eo) with pericentric inversion of chromosome 16 is cytomorphologically defined by a myelomonoblastic blast population and abnormal eosinophils. Until now, it remained an open question whether these abnormal eosinophils are part of the malignant clone or an epiphenomenon. We analyzed five cases of AML M4Eo with inv(16) and combined May-Grünwald-Giemsa staining with fluorescence in situ hybridization using yeast artificial chromosome clone 854E2, which spans the inv(16) breakpoint on 16p. In the case of inv(16), three instead of the normal two hybridization signals can be observed both on metaphase spreads and in interphase cells. With this approach, we were able to show inversion 16 in abnormal eosinophils and, therefore, identified them as a part of the leukemic cell population.</p>

<p>Purpose: To examine the influence of α-particle radiation exposure from internally deposited plutonium on chromosome aberration frequencies in peripheral blood lymphocytes of workers from the Sellafield nuclear facility, UK. Materials and methods: Chromosome aberration data from historical single colour fluorescence in situ hybridization (sFISH) and Giemsa banding (G-banding) analyses, together with more recent sFISH results, were assessed using common aberration analysis criteria and revised radiation dosimetry. The combined sFISH group comprised 29 men with a mean internal red bone marrow dose of 21.0 mGy and a mean external γ-ray dose of 541 mGy. The G-banding group comprised 23 men with a mean internal red bone marrow dose of 23.0 mGy and a mean external γ-ray dose of 315 mGy. Results: Observed translocation frequencies corresponded to expectations based on age and external γ-ray dose with no need to postulate a contribution from α-particle irradiation of the red bone marrow by internally deposited plutonium. Frequencies of stable cells with complex aberrations, including insertions, were similar to those in a group of controls and a group of workers with external radiation exposure only, who were studied concurrently. In a similar comparison there is some suggestion of an increase in cells with unstable complex aberrations and this may reflect recent direct exposure to circulating lymphocytes. Conclusions: Reference to in vitro dose response data for the induction of stable aberrant cells by α-particle irradiation indicates that the low red bone marrow α-particle radiation doses received by the Sellafield workers would not result in a discernible increase in translocations, thus supporting the in vivo findings. Therefore, the greater risk from occupational radiation exposure of the bone marrow resulting in viable chromosomally aberrant cells comes from, in general, much larger γ-ray exposure in comparison to α-particle exposure from plutonium.</p>