Proliferative Fasciitis

Definition

Subcutaneous or fascial reactive process composed of large ganglion-like cells, fibroblasts and myofibroblasts set in a myxoid stroma

Predominantly involves subcutaneous tissue
- May appear grossly infiltrative
- May extend along fascia
Generally loose myxoid stroma
- May contain collagen
  - May hyalinize
- May have central arborizing vascular pattern
- Small vessels often arranged in clusters or in a linear fashion
Spindled and stellate fibroblasts and myofibroblasts
- Vesicular nuclei
- No cytologic atypia
Ganglion-like cells
- Characteristic feature of this process
- Large round regular nuclei
- Occasional binucleate and trinucleate cells may be seen
- Prominent nucleoli
- Dispersed chromatin
- Basophilic to amphophilic cytoplasm
- May be clustered and may mold each other
Mitotic figures frequent
- No atypical mitotic figures
Rare lesions in children have some differences
- Reported age range 2 months to 13 years
- Better circumscription
- Lobulated
- More cellular
- More ganglion-like cells, fewer fibroblasts
- May show focal necrosis and acute inflammation

Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342