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
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
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
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
Richard L Kempson MD
Original posting: March 1, 2008
Supplemental studies
Immunohistology
Muscle specific actin
Positive
Smooth muscle actin
Positive
S100
Negative
Desmin
Negative
Beta-catenin
Negative
ALK
Negative
Keratin
Negative
MyoD1
Negative
Myogenin
Negative
Differential diagnosis
Proliferative Myositis Nodular Fasciitis
Ganglion-like cells present
No ganglion-like cells
No damage to muscle fibers resulting in a checkerboard pattern with lesional cells between patches of intact muscle
Muscle fibers obliterated or damaged
Nodular fasciitis may occasionally involve muscle
Sarcomas (General)
Nodular Fasciitis
Usually over 4 cm
Rare over 5 cm
Frequent cellular pleomorphism
No pleomorphism
Atypical mitotic figures common
Atypical mitotic figures rare
Coarse, granular, irregular chromatin
Fine, pale, even chromatin
Nodular Fasciitis Low Grade Fibromyxoid Sarcoma
Usually superficial
Usually deep soft tissues
S and C shaped bundleslll of cells
Alternating fibrous and myxoid areas with whorling
Small
Usually large
Essentially never metastasizes
Metastatic rate reported from 6-60%, probably closer to 10%
LGFS may contain areas indistinguishable from nodular fasciitis; both are composed of bland cells
Inflammatory Myofibroblastic Tumor Nodular Fasciitis
Frequently over 5 cm
Rarely over 5 cm
Usually in children
Rare in children
Frequently involves abdominal cavity
Does not involve abdominal cavity
Variable patterns
Usually loose pattern throughout
Prominent inflammatory cells
Only scattered inflammatory cells
Myositis Ossificans
Nodular Fasciitis
Always involves muscle
May involve muscle
Zonal osteoid and bone
Focal bone formation
Intramuscular Myxoma Nodular Fasciitis
Very hypocellular
Moderately cellular
No grouping of cells
Undulating bundles of cells
No tissue culture appearance
Tissue culture appearance with tears and spaces in tissue
Rare mitotic figures
Frequent mitotic figures
Juxta-articular Myxoma Nodular Fasciitis
No grouping of cells
Undulating bundles of cells
No tissue culture appearance
Tissue culture appearance with tears and spaces in tissue
Rare mitotic figures
Frequent mitotic figures
Benign Myxoid Nerve Sheath Tumors
Nodular Fasciitis
Mitotic figures rare
Mitotic figures frequent
S100 essentially always positive
S100 negative
Plexiform Fibrohistiocytic Tumor Nodular Fasciitis
More mature collagenous stroma
Loose, immature stroma
Small, dense nuclei
Vesicular nuclei
Mitotic figures usually rare
Mitotic figures frequent
Nodules of histiocytes frequent
Foam cells and histiocytes infrequent
Plexiform rays of fibrous tissue
Loose C and S shaped bundles of cells
Fibromatosis, Abdominal Desmoid and Extra-abdominal Desmoid
Nodular Fasciitis
Usually dense collagenous stroma
Collagenous stroma focal or rare
Linear fascicles of cells
Undulating bundles of cells
Infrequent mitotic figures
Frequent mitotic figures
Usually >3 cm
Usually <4 cm
Beta-catenin 80-90%
Beta-catenin negative
Nodular Fasciitis Myofibroma
Lacks biphasic pattern
Biphasic nodular pattern
Lacks HPC-like vascular pattern
Frequent HPC-like vascular pattern
Multiple lesions rare
25% of cases multifocal
Desmin variable
Desmin negative
Clinical
Uncommon in children and over age 65 years
Pediatric lesions more commonly in head and neck
Uncommon in lower extremity and hands
Does not involve abdominal cavity
Typically rapid growth
Rarely multiple
Recurrence following excision is very rare
Regression frequent even after partial excision
Bibliography
Kempson RL, Fletcher CDM, Evans HL, Henrickson MR, Sibley RS. Tumors of the Soft Tissues, Atlas of Tumor Pathology, AFIP Third Series, Fascicle 30, 2001
Fletcher CDM, Unni KK, Mertens F. Pathology and Genetics of Tumours of Soft Tissue and Bone, World Health Organization Classification of Tumours 2002
Weiss SW, Goldblum JR. Enzinger and Weiss's Soft Tissue Tumors, 5th edition, 2008
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Patterson JW, Moran SL, Konerding H. Cranial fasciitis. Arch Dermatol 1989 May;125(5):674-8
Hutter R, Foote F, Francis K, et al. Parosteal fasciitis. A self-limited benign process that simulates a malignant neoplasm. Am J Surg 1962; 104:800-12
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