Soft tissue

Fibroblastic / myofibroblastic

Nodular fasciitis

Editor-in-Chief: Debra L. Zynger, M.D.
Brendan C. Dickson, M.D., M.Sc.

Last author update: 6 August 2019
Last staff update: 10 November 2022 (update in progress)

Copyright: 2002-2023,, Inc.

PubMed Search: Nodular fasciitis [title] soft tissue

Brendan C. Dickson, M.D., M.Sc.
Page views in 2022: 47,650
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Cite this page: Dickson BC. Nodular fasciitis. website. Accessed February 8th, 2023.
Definition / general
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 be the result of 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 RNA sequencing
Radiology description
Radiology images

Images hosted on other servers:

Images from

MRI digital nerve


MRI shoulder

Prognostic factors
  • Not applicable; nodular fasciitis is considered benign
Case reports
Clinical images

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Digital nerve

Gross description
Gross images

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Small, well circumscribed


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
  • Areas of extravasated erythrocytes often present
Microscopic (histologic) images

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




Extravasated erythrocytes


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 NGS techniques
Molecular / cytogenetics images

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Sample pathology report
  • Soft tissue, neck, biopsy:
    • Nodular fasciitis
    • Comment: This is 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. COL1A1-USP6
  2. PPP6R3-USP6
  3. MYH9-USP6
  4. ARL17A-USP6
Board review style answer #1

Comment Here

Reference: Nodular fasciitis
Board review style question #2

    Which of the following is true about this entity?

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

Comment Here

Reference: Nodular fasciitis
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