Nonspecific esterase

Topic Completed: 4 November 2019

Revised: 4 November 2019

Copyright: 2002-2019,, Inc.

PubMed Search: Nonspecific esterase stain

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Cite this page: Cai C. Nonspecific esterase. website. Accessed November 21st, 2019.
Definition / general
  • Enzyme histochemical stain that relies on endogenous esterase activity to hydrolyze exogenous alpha naphthyl acetate substrate, which yields naphthol, a reddish brown product visible under light microscopy
Essential features
  • Routinely used in skeletal muscle biopsies to detect macrophages, myophagocytosis and denervated myofibers
  • Differentiates macrophages (positive) from lymphocytic inflammation (negative) in muscle biopsies
  • Also highlights neuromuscular junctions and myotendinous junctions in normal skeletal muscle
  • Used in hematopathology to differentiate the monocytic lineage (strongly positive) from the lymphoid and other myeloid lineage cell types (weak punctate or negative)
  • Other names: alpha naphthyl acetate, alpha naphthyl butyrate esterase
  • Note: the abbreviation NSE also refers to neuron specific enolase
  • Cytoplasmic
Uses by pathologists
Microscopic (histologic) description
  • Staining pattern varies depending on structure highlighted
    • Macrophages: strong cytoplasmic (lysosomes)
      • Macrophage associated with myophagocytosis are located within the sarcoplasm of myofibers
      • Macrophages associated with inflammatory myositis are typically located outside myofibers in the perimysial or endomysial connective tissue (Curr Protoc Immunol 2001;Appendix 3)
    • Neuromuscular junction: strong, discrete, subsarcolemmal, clustered around intramuscular nerve (Histochem J 1998;30:7)
    • Denervated myofibers: weak diffuse sarcoplasmic (J Neurol Sci 1975;26:133)
    • Myoteninous junction: irregular linear (Neuromuscul Disord 1996;6:211)
    • Type I fibers are slightly more darkly stained than type II fibers (J Anat 1988;157:79)
Microscopic (histologic) images

Contributed by Chunyu "Hunter" Cai, M.D., Ph.D.

Neuromuscular junction

Myotendinous junction



Denervated myofibers

Inflammatory myositis

Macrophagic myofasciitis

Images hosted on other servers:
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IgA myeloma

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AML M5b (fig 2)

Positive staining - normal
Positive staining - disease
Negative staining - disease
Board review question #1
Which of the following correctly describes the finding in the pictured nonspecific esterase stained muscle?

  1. Denervation
  2. Myophagocytosis
  3. Myotendinous junction
  4. Neuromuscular junction
  5. Type II atrophy
Board review answer #1
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