Alpha Naphthyl Butyrate Esterase Staining Method

**Semantic type:** Laboratory Procedure

**Definition:** A cytochemical staining technique used to detect esterase enzyme contained within monocytes and macrophages, which reacts strongly with the substrate alpha-naphthyl butyrate. Monoblastic [FAB M5a (without differentiation) or M5b (with differentiation)] and acute myelomonocytic (M4) leukemias blasts stain when the butyrate substrate is used. Myeloid cells (either malignant or non-malignant) do not stain with nonspecific esterase techniques.

**Synonyms:** - Alpha Naphthyl Butyrate Esterase Stain