Cup-like blasts are abnormal blasts in which the nucleus shows a deep, bowl-shaped (cup-like) invagination, or a large, diffusely faded nuclear zone. They are seen primarily in acute myeloid leukemia (AML), particularly in subtypes with NPM1 mutations and CD34 negativity. The presence of cup-like blasts is a morphological clue to NPM1-mutated AML. This nuclear abnormality is often more evident in peripheral blood than in bone marrow.