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Salivary glands

Epithelial / myoepithelial tumors

Keratocystoma

Reviewer: Adriana Handra-Luca, M.D. (see Reviewers page)
Revised: 1 February 2013, last major update September 2012
Copyright: (c) 2003-2013, PathologyOutlines.com, Inc.

General
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● Rare benign tumor with multicystic spaces lined by squamous cells with focal solid epithelial nests
● First reported by Seifert (as choristoma, Virchows Arch 1999;434:355) and Nagao (Mod Pathol 2002;15:1005)

Clinical features
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● Very rare neoplasm of children/adults, < 20 cases reported
● Usually parotid gland; may derive from salivary ducts undergoing squamous metaplasia
● Excision appears to be adequate treatment

Case reports
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● 37 year old man with parotid nodule (J Clin Pathol 2010;63:758)

Gross images
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Multicystic tumor filled with keratin

Micro description
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● Benign tumor with multicystic spaces, without lobular architecture, lined by squamous cells with focal solid epithelial nests
● Parakeratotic and orthokeratotic keratinization without a granular layer
● Outer layer has bud-like protrusions
● Cells have abundant eosinophilic cytoplasm and bland, uniform nuclei
● May have collageneous stroma, expansive growth
● Focal foreign-body reaction against keratin
● Occasional normal mitotic figures
● No necrosis, no invasion, no angiolymphatic invasion, no perineurial invasion, no atypia, no mucous cells

Micro images
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Squamous lined cysts filled with keratin


Immunostains

 
37 year old man with parotid tumor

Positive stains
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● Cytokeratin (AE1-AE3, CK14, CK17; focal CK13, focal CK19), Ki-67 (outer basal layer only), collagen type IV positive material around cysts/cell nests

Negative stains
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● Alpha smooth muscle actin, S100, CK8, CK18

Differential diagnosis
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● Epidermal/dermoid cysts
● Mucoepidermoid carcinoma
● Necrotizing sialmetaplasia
● Squamous cell carcinoma
● Squamous metaplasia in other conditions

End of Salivary glands > Epithelial / myoepithelial tumors > Keratocystoma

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