MPO and acute myeloid leukemia: However, a subset of patients with a PICALM-MLLT10 fusion (3 of 23 in one series) have a mediastinal mass, no expression of T-cell antigens, and positive expression of myeloid antigens such as CD33, CD34, or MPO, and were given a diagnosis of M1 AML or acute undifferentiated leukemia (AUL)43.