Soft tissue

Fibroblastic / myofibroblastic

Proliferative fasciitis

Last author update: 1 June 2013
Last staff update: 6 June 2022

Copyright: 2002-2022,, Inc.

PubMed Search: Proliferative fasciitis [title]

Meggen Walsh, D.O., M.S., P.A.
Jerad M. Gardner, M.D.
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Cite this page: Walsh M. Proliferative fasciitis. website. Accessed July 3rd, 2022.
Definition / general
  • Subcutaneous or fascial proliferation similar to nodular fasciitis, but with large basophilic cells resembling ganglion cells (Cancer 1975;36:1450, Stanford University)
  • Histologically the same as proliferative myositis, but not located in muscle
Clinical features
  • Usually adults (mean age 50 years)
  • Forearm is most common location (2/3 located in the forearm), also trunk or proximal extremities
  • Rare in patients under 15 years old (but see childhood variant below
  • Rapid growth but benign behavior
Case reports
  • Local excision
Gross description
  • Usually 3 cm or less, poorly circumscribed subcutaneous mass that may extend horizontally along fascia

Childhood variant:
Microscopic (histologic) description
  • Resembles nodular fasciitis due to zonation effect, tissue culture type growth and plump fibroblastic and myofibroblastic spindle cells, but has large ganglion-like cells with abundant amphophilic to basophilic cytoplasm, round vesicular nuclei (occasionally 2 - 3 nuclei) and prominent nucleoli
  • Ill defined margins
  • Stroma is collagenous or myxoid, often with focal myxoid cystic degeneration
  • Often arborizing vascular pattern
  • Variable mitotic figures but no atypical ones

Childhood variant:
  • More cellular than adult form with prominent ganglion-like cells and pleomorphism resembling rhabdomyoblasts
  • May have many mitotic figures
  • May have acute inflammatory cells and focal necrosis (unusual in adult form)
  • Often no / minimal fibroblasts
  • Pushing border instead of infiltrative like adult form
Microscopic (histologic) images

AFIP images

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Fig 1: Prominent hemorrhage and vague centering of cellular proliferation on interlobar septa of subcutaneous fat
Fig 2: Mixture of ganglion-like cells, myofibroblasts and inflammatory cells
Fig 3: Ganglion-like cells have abundant amphophilic cytoplasm and prominent nucleoli
Fig 4: Ganglion-like cells mixed with inflammatory cells within myxohyaline matrix
Fig 5: Condensed around thin walled vascular channel

Contributed by Mark R. Wick, M.D.

Contributed by Dr. Meggen Walsh and Dr. Dana Richards
Childhood variant:

Ganglion-like cells

Ganglion-like cells with infiltrate

Lobulated growth pattern

Images hosted on other servers:

Myofibroblasts and fibroblasts

Ganglion-like cells

van Gieson stain

Alcian blue-PAS

Cytology description
  • Cellular smear with spindle cells and large cells with abundant cytoplasm, one to two eccentric nuclei and macronucleoli (Acta Cytol 1985;29:882)
Positive stains
Negative stains
Differential diagnosis
  • Ganglioneuroma: background spindle cell proliferation similar to neurofibroma, ganglion cells and spindle cells are positive for neural markers such as S100
  • Nodular fasciitis: no or very few ganglion-like cells
  • Proliferative myositis: histologically identical, but intramuscular location
  • Rhabdomyosarcoma: background spindle cells appear malignant rather than fasciitis-like; rhabdomyoblasts may have striations; desmin+, myogenin+
  • Sarcoma: large mass, nuclear atypia and pleomorphism in background spindle cells, atypical mitotic figures, often tumor necrosis

Childhood variant:
  • Rhabdomyosarcoma: rhabdomyoblasts may have cross striations (unlike ganglion-like cells); desmin+, myogenin+
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