Butyrate Esterase is a stain which is specific for white blood cells of the Monocytic proliferation line. It is commonly used in the diagnosis of leukemia

Leukemia

Leukemia or leukaemia is a type of cancer of the blood or bone marrow characterized by an abnormal increase of immature white blood cells called "blasts". Leukemia is a broad term covering a spectrum of diseases...

 when staining touch preparation type slides of bone marrow

Bone marrow

Bone marrow is the flexible tissue found in the interior of bones. In humans, bone marrow in large bones produces new blood cells. On average, bone marrow constitutes 4% of the total body mass of humans; in adults weighing 65 kg , bone marrow accounts for approximately 2.6 kg...

. It is instrumental in the diagnosis of monocytic leukemia

Monocytic leukemia

Monocytic leukemia is a type of myeloid leukemia characterized by a dominance of monocytes in the marrow. When the monocytic cells are predominantly monoblasts, it is subclassified into monoblastic leukemia....

s and the myelomonocytic variant of acute myelocytic leukemia (FAB classification M4).