[The study of 4 cases of myeloid neoplasm with t (5;12) (q33;p13) and the literatures review].

OBJECTIVE: To report clinical and laboratory features of 4 cases of myeloid neoplasm with t (5;12) (q33;p13).

METHODS: Cytogenetic examination of bone marrow cells obtained from patients was performed by 24 h culture method. R banding technical was used for karyotype analysis. PDGFRβ gene rearrangement was detected by FISH using dual color break apart PDGFRβ probe. ETV6-PDGFRβ fusion genes were detected by multiple-reverse transcription polymerase chain reaction (RT-PCR). Direct sequencing analysis was performed on the PCR products in case 1. Immunophenotype analysis was carried out by flow cytometry. Four cases were treated with imatinib (IM) and followed up.

RESULTS: The diagnoses included 3 MPN and 1 AML-M2. The t (5;12) (q33;p13) was a primary abnormality in 3 cases of MPN and a secondary abnormality in 1 case of AML-M2. PDGFRβ gene rearrangement and ETV6-PDGFRβ fusion genes were detected by FISH and multiple-RT-PCR in 4 cases, respectively. The immunophenotypical analysis of leukemia cells showed positive for CD13, CD33 and CD34. Two cases obtained MMR after the treatment of IM, one case complete hematologic and complete cytogenetic response. ETV6-PDGFRβ was negative detected by multiple-RT-PCR after the treatment of IM, but relapsed and died soon in case 4.

CONCLUSIONS: The t (5;12) myeloid neoplasm was a subtype with unique features. The t (5;12) maybe a primary chromosome abnormality in MPN and a secondary in AML. MPN with t (5;12) could benefit from IM, but not for AML. Dual-FISH was a reliable tool for detecting PDGFRβ rearrangement.