New variant translocation in acute myelomonocytic leukemia with bone marrow eosinophilia

Uneven frequencies of secondary chromosomal abnormalities in acute myeloid leukemias with t(8;21), t(15;17), and inv(16)

The types and incidences of secondary chromosomal abnormalities were analyzed in three subtypes of leukemia with recurrent abnormalities, translocations t(8;21), t(15;17), and inversion inv(16). The main types of clonal secondary abnormalities were similar to those described in the literature, loss of sex chromosome associated with t(8;21), trisomy 8 with t(15;17), and trisomies 8 or 22 with inv(16). On the whole, the incidence of clonal abnormalities was significantly higher in t(8;21) leukemia than in the two other subtypes. This difference was not related to a chromosomal instability peculiar to this leukemia subtype, because the incidence of nonclonal abnormalities was the same in the three types of leukemia studied. The significance of secondary clonal abnormalities remains speculative. A careful comparative analysis of structural rearrangements of the chromosomes usually involved in secondary abnormalities must be carried out as a first step to identify the key genes altered.

Variant three-way translocation of inversion 16 in AML-M4Eo confirmed by fluorescence in situ hybridization analysis

The inv(16) and t(16;16) characterize a subgroup of acute myelomonocytic leukemia (AML) with distinct morphological features and a favorable prognosis. Both cytogenetic abnormalities result in a fusion of CBF beta at 16q22 and MYH11 gene at 16p13, whose detection by PCR and fluorescence in situ hybridization (FISH) is useful for diagnosis and monitoring of the disease. Variant translocations of inv(16)/t(16;16) are very rare and whether they are also associated with a favorable prognosis is unknown. We report a patient presenting with typical AML-M4Eo and a three-way translocation of inv(16) involving 16p13, 16q22, and 3q22. FISH studies on bone marrow (BM) chromosomes using CBFB and MYH11 DNA probes revealed a fusion of CBFB and MYH11 on 16q of the der(16), as well as a signal from MYH11 on 16p but not from CBFB; normal signals for both probes were present on the normal 16. Neither of these labeled probes was on the der(3), but the translocation between the der(3) and der(16) was confirmed by using a chromosome 16 painting probe. Molecular analysis of BM cells using RT-PCR identified a CBFB-MYH11 fusion transcript type D. After achieving complete remission, the patient relapsed. We conclude that FISH and PCR are feasible tools to distinguish cases with variant abnormalities of inv(16) from cases with other chromosome 16 abnormalities. Variant abnormalities of inv(16) may be not associated with favorable prognosis.

Deletion of the long arm of chromosome 7 in myelomonocytic leukemia with bone marrow eosinophilia

We report a 62-year-old man with acute myelomonocytic leukemia with bone marrow eosinophilia (M4Eo), and a deletion of the long arm of chromosome 7. The patient presented with pancytopenia, which shortly after evolved to overt leukemia. There was no response to the daunorubicin-cytosine arabinoside (Ara-C) regimen, and a remission achieved with amsacrine (AMSA)-Ara-C lasted only for a short time. On relapse, a peculiar skin rash accompanied the hematologic picture. While ANLL with chromosome 7 abnormalities usually carries adverse prognosis, patients with M4Eo (which is usually associated with chromosome 16 abnormalities) do better. The patient described here examplifies that M4Eo may be associated with del(7)(q22), and that it is the chromosomal abnormality rather than the type of leukemia that might determine the clinical outcome.

Inversion-associated translocations in acute myelomonocytic leukemia with eosinophilia

Cytogenetic studies of three acute myelomonocytic leukemias with bone marrow eosinophilia (M4EO) revealed chromosome 16 inversion associated with additional abnormalities. The inverted chromosome 16 was involved in two patients. Fluorescence in situ hybridization (FISH) experiments with a YAC probe detecting inv(16) showed that the translocation breakpoints involving chromosome 16 did not implicate the inversion breakpoints. FISH can thus distinguish between true variant translocations and translocations with other breakpoints on chromosome 16 in M4EO.