Which AML subtype is typically associated with strong nonspecific esterase positivity indicating monocytic differentiation?

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Monocytic differentiation in AML is shown by cytochemical staining for nonspecific esterase, which is strongly positive in monocytes and macrophages. This NSE positivity is typically tartrate-sensitive and serves as a hallmark of monocytic lineage.

In the FAB classification, the acute monocytic leukemia category corresponds to AML-M5. It is defined by prominent monocytic proliferation, so strong NSE staining fits this subtype best. The other AML categories show different maturation patterns: AML-M0 lacks differentiation, AML-M4 has myeloid with monocytic features but not as exclusively monocytic, and AML-M3 is acute promyelocytic leukemia with promyelocytes and Auer rods rather than monocytic differentiation evidenced by NSE.

Thus, the strong nonspecific esterase positivity indicating monocytic differentiation points to acute monocytic leukemia.