Soft tissue
Fibroblastic / myofibroblastic tumors
Nodular fasciitis


Topic Completed: 6 August 2019

Revised: 6 August 2019

Copyright: 2002-2019, PathologyOutlines.com, Inc.

PubMed Search: Nodular fasciitis [title] soft tissue

Brendan C. Dickson, M.D., M.Sc.
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Cite this page: Dickson BC. Nodular fasciitis. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/softtissuenf.html. Accessed August 24th, 2019.
Definition / general
Essential features
Terminology
  • Pseudosarcomatous fasciitis (obsolete)
ICD coding
  • ICD-10: M72.4 - pseudosarcomatous fibromatosis
Epidemiology
Sites
Pathophysiology
  • 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)
Etiology
  • 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
Diagnosis
  • 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

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Images from Radiopaedia.org

MRI digital nerve

Mammogram

MRI shoulder

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

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Digital nerve

Gross description
Gross images

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Small, well circumscribed

Breast

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.

Cellular

Storiform

Myxoid

Extravasated erythrocytes

Colllagenous

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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USP6 FISH

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 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 answer #1
C. MYH9-USP6

Reference: Nodular fasciitis

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Board review 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 answer #2
C. Benign and self limiting

Reference: Nodular fasciitis

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