Therapy-related myelodysplastic syndrome with trisomy 1q due to der(1;7) and megakaryoblastic proliferation developing during complete remission of therapy-related acute myeloid leukemia with t(8;21).

Therapy-related acute myeloid leukemia (t-AML) with t(8;21) and therapy-related myelodysplastic syndrome (t-MDS) with trisomy 1q due to der(1;7) developed in the same patient with T-cell lymphoma at intervals of six years. After the development of t-MDS with trisomy 1q, during complete remission of t-AML, the number of megakaryoblasts increased to maximally 74% of leukocytes in the blood. This is a very rare case of two separate therapy-related myeloid malignancies (early t-AML and late t-MDS) and is also a notable case of t-MDS with trisomy 1q due to der(1;7) accompanied by megakaryoblastic proliferation.