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Reviewer: Nat Pernick, M.D. (see Reviewers page)
Revised: 29 June 2012, last major update June 2012
Copyright: (c) 2002-2012, PathologyOutlines.com, Inc.


● Also called muramidase
● Histiocytic enzyme that cuts muramic acid linkages in walls of bacterial cells (Wikipedia)

Uses by pathologists

● Common marker for histiocytes / monocytes, including monocytic component of leukemias (M4, M5)

Micro images

Acute myelomonocytic leukemia (M4)

Orbit: myeloid sarcoma

Soft tissue: hemosiderotic fibrohistiocytic lipomatous lesion

Thyroid gland: histiocytes stain strongly in palpation thyroiditis

Vagina: myeloid sarcoma

Positive staining - normal

● Nonspecific stain for histiocytes (granulomas), monocytes, neutrophils
● May also stain some epithelial cells (pleomorphic adenoma)
● Goblet cells and related lesions (goblet cell carcinoid)
● Breast lactating lobules

Positive staining - disease

● Acinic cell carcinoma (breast, salivary gland, Am J Surg Pathol 2009;33:1137)
● Acute myelomonocytic leukemia (M4), acute monocytic leukemia (M5)
● Adenocarcinoma (various sites)
● Ampulla: Paneth cell carcinoma
● CNS: chordoma
● Eye: oncocytoma of conjunctiva
● Histiocytic lesions: histiocytoma, histiocytic sarcoma, Rosai Dorfman disease
● Langerhans cell histiocytosis
● Mastocytosis
● Myeloid sarcoma
● Renal collecting duct / Bellini duct carcinoma
● Salivary gland intercalated duct lesions (Am J Surg Pathol 2009;33:1322)
● Skin: granuloma annulare, multicentric reticulohistiocytosis, synovial metaplasia, xanthogranuloma
● Spleen: angiosarcoma and hemangioma (often, Mod Pathol 2000;13:978), littoral cell angioma

Negative staining

● Breast: histiocytoid variant of lobular carcinoma
● Dendritic cells
● Inflammatory pseudotumor
● Interdigitating dendritic cell sarcoma
● Skin: necrobiosis lipoidica

End of Stains > Lysozyme

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