Therefore, a combination of cMPO, CD34, HLADR, CD117, CD33, CD15, CD11c, CD64, CD9, and CD18 can diagnose APL with high specificity and sensitivity by excluding other hypergranular AML as few cases of NPM1-positive AML mimicking APL on morphology and also in cases showing CD34 and HLA-DR negativity on flow cytometry, that can pose a diagnostic dilemma. The gene discussed is CD9; the disease is acute promyelocytic leukemia.