Table of Contents
Definition / general | Clinical features | Case reports | Treatment | Gross description | Microscopic (histologic) description | Microscopic (histologic) images | Cytology description | Positive stains | Negative stains | Differential diagnosisCite this page: Walsh M. Proliferative fasciitis. PathologyOutlines.com website. https://www.pathologyoutlines.com/topic/softtissueproliferativefasciitis.html. 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
- 35 year old Japanese woman with rapid involution of mass (Skeletal Radiol 2004;33:300)
Treatment
- Local excision
Gross description
- Usually 3 cm or less, poorly circumscribed subcutaneous mass that may extend horizontally along fascia
Childhood variant:
- Circumscribed, lobulated white firm mass, 1.5 to 3 cm (Am J Surg Pathol 1992;16:364)
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
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:
Images hosted on other servers:
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
- Spindle cells: smooth muscle actin, muscle specific actin
- Ganglion-like cells: vimentin, focal or membranous actin
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+