Alpha Naphthyl Esterase Staining Method

**Semantic type:** Laboratory Procedure

**Definition:** A cytochemical staining technique using the alpha-naphthyl esterase staining method or a nonspecific esterase staining method to identify and quantify monoblasts and monocytes and to detect esterase activity. The esterase enzyme contained within monocytes and macrophages reacts strongly with the substrate alpha-naphthyl butyrate. The test is useful in diagnosis of acute leukemias. It marks immature monocytes, and thus is useful in the diagnosis of acute myelogenous leukemia of monocytic type.

**Synonyms:** - Alpha Naphthyl Esterase Stain