Nodular Fasciitis
Definition
- Reactive soft tissue lesion composed of undulating bundles of loosely arranged fibroblasts and myofibroblasts
Diagnostic Criteria
- Cells loosely arranged in C or S shaped bundles
- May be storiform
- Feathery or tissue culture-like appearance
- Appears to have holes and tears in tissue
- Stromal mucin accumulates in pools
- Uniform elongate nuclei
- No pleomorphism
- Usually enlarged and vesicular
- Pale, fine, even chromatin
- Small nucleoli
- Frequent normal mitotic figures
- Abnormal mitotic figures very rare
- Small thin walled blood vessels
- May have an arborizing pattern
- Extravasated blood cells
- Hemosiderin and foamy macrophages rare
- Scattered lymphocytes, frequently near periphery
- Noncircumscribed, may infiltrate along fascial planes
- Virtually always under 5 cm diameter
- Usually under 3 cm
- May occur from subcutis to skeletal muscle or periosteum
- Occasional features, may be focal or predominant
- Bone or cartilage formation
- Most often in parosteal or cranial variants
- Rarely may be seen focally in other sites
- Vascular involvement
- If prominent may be termed intravascular fasciitis
- Hyalinization of stroma
- May resemble keloid or desmoid fibromatosis
- Multinuclear osteoclast-like giant cells
- Cyst formation due to abundant mesenchymal mucin
- Central necrosis and fibrin
- Bone or cartilage formation
- Variants defined by location
- Parosteal fasciitis
- Forms metaplastic bone
- Focal metaplastic bone may be seen rarely in lesions not near bones
- Such lesions have been termed ossifying fasciitis or fasciitis ossificans
- Intravascular fasciitis
- Small to large veins and arteries may be involved
- More often contains giant cells
- Variable patterns
- Typically extravascular nodular fasciitis with focal or extensive vascular involvement
- Predominantly or exclusively intravascular
- May extend through vessel and become multinodular
- Cranial fasciitis
- Most common in infants and children
- Involves skull and soft tissue of scalp
- May involve dura and meninges
- Giant cells common
- May have necrosis, bone formation
- May be larger than 3 cm
- Intramuscular fasciitis
- Involves skeletal muscle
- Damaged muscle fibers may have large hyperchromatic nuclei
- Usually multinucleated
- Parosteal fasciitis
Richard L Kempson MD
Robert V Rouse MD
Department of Pathology
Stanford University School of Medicine
Stanford CA 94305-5342
Original posting: March 1, 2008
Last update: June 15, 2008
