Soft tissue

Fibroblastic / myofibroblastic

Nodular fasciitis

Editorial Board Member: Jose G. Mantilla, M.D.
Deputy Editor-in-Chief: Borislav A. Alexiev, M.D.
Editor-in-Chief: Debra L. Zynger, M.D.
Brendan C. Dickson, M.D., M.Sc.

Last author update: 9 March 2023
Last staff update: 9 March 2023

Copyright: 2002-2023,, Inc.

PubMed Search: Nodular fasciitis

Brendan C. Dickson, M.D., M.Sc.
Page views in 2022: 47,650
Page views in 2023 to date: 55,817
Cite this page: Dickson BC. Nodular fasciitis. website. Accessed November 29th, 2023.
Definition / general
  • Neoplasm of fibroblastic / myofibroblastic derivation that is typically benign and self limited
  • Virtually all cases contain fusion genes; MYH9::USP6 is the most common fusion product, although other USP6 partners have been identified (Lab Invest 2011;91:1427, Mod Pathol 2017;30:1577)
Essential features
  • Pseudosarcomatous fasciitis (obsolete)
  • Cranial fasciitis
ICD coding
  • ICD-10: M72.4 - pseudosarcomatous fibromatosis
  • Virtually all cases contain fusions genes; MYH9::USP6 is the most common fusion product, although many other genes may partner with USP6 (Mod Pathol 2017;30:1577)
  • Historically tumors were thought to result from trauma, although this is now considered unlikely
  • Tumors appear to be sporadic and of unknown etiology
Clinical features
  • Tumors are morphologically distinctive and typically amenable to classification on the basis of H&E
  • There is a limited role for immunohistochemistry as tumors show a myofibroblastic immunophenotype
  • USP6 rearrangement can be confirmed by FISH, PCR or next generation sequencing
Radiology description
Prognostic factors
  • Not applicable; nodular fasciitis is considered benign
Case reports
  • Simple excision is generally curative
  • Occasionally may spontaneously regress (e.g., following biopsy)
  • Rarely recurs after incomplete excision
Clinical images

Images hosted on other servers:
Digital nerve

Digital nerve

Gross description
Gross images

Images hosted on other servers:


Microscopic (histologic) description
  • Variable cellularity
  • Extracellular matrix ranges from myxoid to collagenous
  • Older lesions may be more collagenous
  • Areas of cystic degeneration may be identified
  • Spindle stellate cells with a loose fascicular to storiform pattern (so called tissue culture-like and feathery growth)
  • Bland ovoid nuclei
    • Mitotic activity may be conspicuous; however, atypical figures are not a feature
  • Scattered lymphocytes, histiocytes and osteoclast type giant cells often present
  • Exceptionally rare tumors may have malignant morphologic features, including pleomorphism or atypical mitotic figures; in this context, a relationship with nodular fasciitis can only be made following molecular confirmation of USP5 rearrangement (Virchows Arch 2021;479:623, Int J Surg Pathol 2021;29:642, Virchows Arch 2021;479:1007)
Microscopic (histologic) images

Contributed by Brendan C. Dickson, M.D., M.Sc.






Extravasated erythrocytes

Extravasated erythrocytes

Collagenous Collagenous


Electron microscopy description
  • Ultrastructural features typical of fibroblasts; in addition, there are peripheral, longitudinal, myofilaments and hemidesmosome-like structures (Cancer 1976;38:2378)
Molecular / cytogenetics description
  • Majority contain MYH9::USP6 fusion genes (Lab Invest 2011;91:1427)
  • USP6 rearrangement can be established by FISH, PCR or next generation sequencing techniques
Molecular / cytogenetics images

Images hosted on other servers:
<i>USP6</i> FISH


Sample pathology report
  • Soft tissue, neck, biopsy:
    • Nodular fasciitis (see comment)
    • Comment: This is a spindle stellate cell neoplasm arranged in short bundles and fascicles. The nuclei are ovoid and monomorphic, with occasional mitotic activity. The stroma is variably myxoid to collagenous, with scattered lymphocytes and extravasated erythrocytes. The cells are positive for smooth muscle actin; they are negative for desmin, S100, CD34 and epithelial membrane antigen.
Differential diagnosis
Board review style question #1
Most cases of nodular fasciitis are characterized by which of the following gene fusions?

  1. ARL17A::USP6
  2. COL1A1::USP6
  3. MYH9::USP6
  4. PPP6R3::USP6
Board review style answer #1

Comment Here

Reference: Nodular fasciitis
Board review style question #2

Which of the following is generally true about the entity seen in the image above?

  1. Benign and self limiting
  2. Benign with frequent local recurrence
  3. Malignant and frequently metastasizing
  4. Malignant with frequent local recurrence
Board review style answer #2
A. Benign and self limiting

Comment Here

Reference: Nodular fasciitis
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