Abnormal chromatin clumping can be observed in myelodysplastic syndromes, myeloproliferative syndromes, acute leukemias and the abnormal chromatin clumping syndrome. It occurs mainly in mature and semimature blood cells. We report a case of acute myeloid leukemia with trilineage myelodysplasia (AML/TMDS) in which there was chromatin clumping in blast cells.