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Factor XIIIa

Reviewer: Nat Pernick, M.D. (see Reviewers page)
Revised: 9 August 2012, last major update August 2012
Copyright: (c) 2002-2012, PathologyOutlines.com, Inc.


● Fibrohistiocytic marker; note that peritumoral cells may also exhibit Factor XIIIa staining
● Also active form of factor XIII, an enzyme of coagulation system that crosslinks fibrin (Wikipedia)

Uses by pathologists

● Marker of fibrohistiocytic proliferations
● Marker of dermal dencrocytes
● Differentiate dermatofibrosarcoma protuberans (CD34+, D2-40-, Factor XIIIa-) from dermatofibroma (CD34-, Factor XIIIa+, D2-40+)

Micro images

Atypical fibroxanthoma


Epithelioid fibrous histiocytoma

Fibrohistiocytic proliferation with dermal nevus (fig c)

Fibrohistiocytic proliferation with melanoma (fig c)

Positive staining - normal

● Dermal dendrocytes

Positive staining - disease

● Soft tissue: benign fibrous histiocytoma and variants, malignant fibrous histiocytoma
● Also calcifying fibrous tumor (Mod Pathol 2001;14:784), verruciform xanthoma
● Also atypical fibroxanthoma (focal), hemangiopericytoma (scattered), myofibroblastoma in lymph nodes (variable), pleomorphic hyalinizing angiectatic tumor (focal), storiform collagenoma (scattered)
● Cervix: aggressive angiomyxoma
● CNS: Erdheim-Chester disease

Negative staining

● Dermatofibrosarcoma protuberans (usually), Langerhans cell histiocytosis
● Solitary fibrous tumor (Int J Gynecol Pathol 2010;29:189)

End of Stains > Factor XIIIa

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