Factor XIIIa

Author: Nat Pernick, M.D. (see Authors page)

Revised: 16 December 2015, last major update August 2012

Copyright: (c) 2003-2015,, Inc.

PubMed Search: Factor XIIIa
Definition / General
  • 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

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Epithelioid fibrous histiocytoma

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Atypical fibroxanthoma

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Fibrohistiocytic proliferation with dermal nevus (fig c)

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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