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 Bone and Soft-Tissue Disorders

= DESMOID TUMOR [desmos, Greek = band / tendon]

= AGGRESSIVE FIBROMATOSIS = DEEP FIBROMATOSIS = MUSCULOAPONEUROTIC FIBROMATOSIS

= musculoaponeurotic mass characterized by fibrous soft-tissue proliferation disrupting adjacent muscle + soft-tissue planes

Frequency: 1.5–3.0% of all soft-tissue masses

Origin: connective tissue of muscle, fascia, aponeurosis

Genetics: trisomies on chromosomes 8 + 20 (in many cases)

Association:

  1. sporadic
  2. familial polyposis, Gardner syndrome

Classification: according to location

Peak age: 3rd decade (range, puberty to 40 years)

Histo: elongated spindle-shaped cells of uniform appearance, separated by dense bands of collagen, infiltration of adjacent tissue (DDx: low-grade fibrosarcoma, reactive fibrosis)

Location: extraabdominal, abdominal wall, intraabdominal

Imaging appearance:

CT:

MR:

  1. early-stage hypercellular and myxoid lesion
    • predominantly hyperintense lesion on T2WI
  2. mature collagenous lesion
    • decrease in signal intensity on T2WI
    • hypointense bands in 62% (= conglomeration of collagen bundles)
    • moderate to marked enhancement

Prognosis: rapid aggressive growth; 50% recurrence rate after local excision; spontaneous regression (rare); malignant transformation (rare)

DDx:

  1. Malignant tumor: metastasis, soft-tissue sarcoma (fibro-, rhabdomyo-, synovio-, liposarcoma), malignant fibrous histiocytoma, lymphoma
  2. Benign tumor: neurofibroma, neuroma, leiomyoma, giant cell tumor of tendon sheath
  3. Acute hematoma

Abdominal Wall Fibromatosis  !!navigator!!

= ABDOMINAL WALL DESMOID

= solitary slow-growing neoplasm characterized by its progressive, locally infiltrative, and aggressive behavior

Frequency: similar to desmoid-type fibromatosis

◊The most common abdominal wall soft-tissue neoplasm!

Cause: ? genetics; estrogenic hormones (← regression after menopause / oophorectomy); trauma + surgery (= cicatricial fibromatosis of cesarean section scar)

Associated with:

  1. Familial adenomatous polyposis
  2. Gardner syndrome

Peak age: 3rd decade; M÷F = 13÷87 esp. young woman of childbearing age

  • during 1st year after childbirth
  • during pregnancy
  • with use of oral contraceptives

Path: solid firm mass with often infiltrative spiculated margin toward skeletal muscle and subcutis; positive for estrogen receptors (in 79%)

  • palpable firm slowly growing deep-seated mass

Location: musculoaponeurosis of rectus abdominis / internal oblique muscle; occasionally external oblique m.

Average size: 3–7 cm in diameter

  • identical to desmoid-type fibromatosis

MR:

  • hypo- to isointense mass to muscle on T1WI
  • variable intensity on T2WI
  • infiltrative border
  • nonenhancing low-signal-intensity bands
  • “fascial tail” sign = linear extension along superficial fascia

CT:

  • ill-defined / well-circumscribed mass
  • iso- / hypoattenuating mass compared to muscle
  • ± enhancement
  • retraction, angulation, distortion of small / large bowel with mesenteric infiltration

US:

  • sharply defined + smoothly marginated mass of low / medium / high echogenicity

Prognosis: locally aggressive; 25–65% recurrence rate

Rx: local resection + radiotherapy, antiestrogen therapy

DDx: scar endometriosis

Intraabdominal Fibromatosis

Age: peak age in 3rd decade, 70% between 20 and 40 years of age; M÷F = 1÷3

Location: mesentery, retroperitoneum, pelvis

  • Most common mesenteric primary tumor!

In 9–18% associated with: familial adenomatous polyposis (Gardner syndrome)

  • masslike with significant displacement of contiguous structures / infiltrative causing compressive encasement

Cx: compression / displacement of bowel / ureter; vascular occlusion and ischemia; intestinal perforation

DDx:

  1. Malignant neoplasm of the mesentery (lymphoma, metastasis, soft-tissue sarcoma, malignant fibrous histiocytoma)
  2. Inflammatory pseudotumor, extrapleural solitary fibrous tumor, GIST

Desmoid-type Fibromatosis  !!navigator!!

= AGGRESSIVE FIBROMATOSIS = MUSCULOAPONEUROTIC FIBROMATOSIS = EXTRAABDOMINAL DESMOID TUMOR

= common benign aggressively growing soft-tissue tumor arising from connective tissue of muscle, fascia, aponeurosis outside abdominal cavity of intermediate malignant potential

Frequency: 2–4÷1,000,000 per year

Peak age: 25–35 years (range, 2nd–4th decade); M÷F = 1÷1.8; more aggressive behavior in children than in adults

  • painless soft-tissue mass with slow insidious growth
  • decreased mobility, reduced joint motion
  • neurologic complaints: numbness, tingling, sharp pain, motor weakness; history of trauma (30%)

Path: firm mass often with spiculated tumor margins infiltrating muscle + subcutaneous tissue

Histo: proliferation of uniform spindle-shaped fibroblasts → poorly defined fascicles within a collagenous stroma

Associated with: Gardner syndrome (1–2%)

Genetics: activation of b-catenin signaling pathway ← APC (adenomatous polyposis coli) gene mutation on long arm of chromosome 5q21-22 (in Gardner syndrome) or somatic b-catenin mutation

Location: shoulder + upper arm (28%), chest wall and paraspinal region (17%), thigh (12%), neck (8%), knee (7%), pelvis / buttock (6%), lower leg (5%), forearm / hand (5%), head (2%); synchronous multicentricity in same extremity (10–15%)

  • head & neck (7–27%): supraclavicular neck >face

Site: centered in an intermuscular location with rim of fat (“split-fat” sign)

Size: mostly 5–10 cm in diameter

  • Imaging appearance depends on cellularity of lesion + amount of collagen and myxoid material within it
  • poorly circumscribed mass infiltrating surrounding soft tissues + fixation to underlying muscle / bone (often)

US:

  • poorly defined hypoechoic soft-tissue mass
  • ± posterior acoustic shadowing in large lesion
  • ± hypervascularity

CT:

  • homogeneous / heterogeneous attenuation
  • iso- / hyper- / hypodense compared to muscle
  • indistinct lesion margins (often)
  • variable degree of enhancementX

MR:

  • poorly defined lesion with irregular margin (50%) ← invasion of fat / muscle
  • lobulated well-defined lesion (50%)
  • “fascial tail” sign = linear extension along fascial planes (83%)
  • slightly hyper- / iso- (90%) / hypointense relative to muscle on T1WI
  • hyperintense (hypercellular) / hyperintense with areas of low intensity (intermixed with fibrous components) / hypointense (hypocellular) on T2WI
  • heterogeneous texture ← linear + curvilinear strands of low SI on CEMR / T2WI (62–91%) ← collagen fibers
  • moderate to marked enhancement (90%)
  • Bone (6–37%)
    • extensive pressure erosion / cortical scalloping without extension into medullary canal
    • skeletal dysplasia of multicentric desmoid-type fibromatosis (19%):
      • Erlenmeyer flask deformity: polyostotic / on affected side only
      • cortical thickening, focal lucent lesions
      • bone islands, osseous excrescences
        Bone scintigraphy:
        • increased uptake on blood flow + blood pool images

        Angio:
        • marked vascular staining ← hypervascularity
  • Breast
    • palpable firm / hard mass
    • history of minor trauma / breast surgery

    Location: pectoralis fascia
    • round / irregular noncalcified mass
    • indistinct / spiculated margins
    • retraction of pectoralis muscle, skin, nipple

Prognosis: 20–75% recurrence within 2 years after surgical excision depending on location + extent (up to 87% local recurrence in <30 years of age; 20% recurrence rate in >20 years of age)

Infantile Myofibromatosis / Myofibroma  !!navigator!!

= GENERALIZED HAMARTOMATOSIS = CONGENITAL MULTIPLE / GENERALIZED FIBROMATOSIS = MULTIPLE VASCULAR LEIOMYOMAS = DESMOFIBROMATOSIS= INFANTILE F / JUVENILE FIBROMATOSIS

= rare disorder characterized by proliferation of fibroblasts

Cause: unknown

Frequency: 22% of all myofibroblastic lesions in childhood

  • Most common fibromatosis in childhood!

Path: well-marginated soft-tissue lesion with scarlike consistency ± infiltration of surrounding tissues

Size: 0.5–7.0 cm in diameter

Histo: spindle-shaped cells in short bundles and fascicles in periphery of lesion with features of both smooth muscle + fibroblasts; centrally hemangiopericytoma-like pattern with necrosis, hyalinization, calcification

Types: solitary÷multicentric form = 1÷2 to 4÷1

  1. Solitary lesion = myofibroma
    • Age:<2 years of age; M >F
    • Histo: contractile myoid cells arranged around thin-walled blood vessels
    • Location (ordered in diminishing frequency):
      • head & neck (⅓): scalp, forehead, orbit, oral cavity (tongue, mandible, maxilla, mastoid bone), parotid
      • trunk >extremities
    • Site: skin muscle, SQ tissue (86%), bone (9%), GI tract (4%)
    • Prognosis: spontaneous regression in 100%; recurrence after surgical excision in 7–10%
  2. Multicentric disease (2–100 lesions) = myofibromatosis
    • Age: at birth (in 60%), <2 years (in 89%); M <F
    • Location: lung (28%), heart (16%), GI tract (14%), pancreas (9%), liver (8%)
    • Site: skin (98%), subcutis (98%), muscle (98%), bone (57%), viscera (25–37%)
    • Prognosis: related to extent + location of visceral lesions with cardiopulmonary + GI involvement as harbingers of poor prognosis (death in 75–80%); spontaneous regression (33%)
  • firm nontender painless nodules in skin, subcutis, muscle
  • ± overlying scarring of skin with ulceration
  • Skeleton
    • Location: any bone may be involved; commonly in calvarium, femur, tibia, rib, pelvis, vertebral bodies; often symmetric
    • Site: metaphysis of long bones
    • Age: early infancy (usually not present at birth)
      • circumscribed eccentric lytic foci with smooth margins 0.5 –1.0 cm in size:
        • sparing of region immediately adjacent to epiphysis
        • well-defined with narrow zone of transition
        • osseous foci may increase in size and number
      • unusual osseous findings:
        • periosteal reaction, pathologic fracture
      • vertebra plana, kyphoscoliosis with posterior scalloping of vertebral bodies
      • with healing → little residual abnormality:
        • resolution of osteolysis
        • formation of sclerotic margin (initially no sclerosis)
        • ± mineralization of center

        NUC (bone scan):
        • increased / little radiotracer uptake

        DDx:
        1. Langerhans cell histiocytosis (skin lesions)
        2. Neurofibromatosis (multiple masses)
        3. Osseous hemangiomas / lymphangiomatosis / lipomatosis
        4. Metastatic neuroblastoma
        5. Multiple nonossifying fibromas
        6. Enchondromatosis
        7. Hematogenous osteomyelitis (unusual organism)
        8. Fibrous dysplasia
  • Soft tissue
    • Most common fibrous tumor in infants
    • round well- / ill-defined solid mass with central necrosis
    • central / peripheral solitary / multiple calcifications
    • prominent vascularity of skin lesions resembling hemangioma

    US:
    • hypo- to isoechoic mass
    • thick peripheral wall / septa
    • anechoic / partially anechoic center
    • echogenic shadowing foci ← calcifications

    CT:
    • attenuation similar to muscle / mildly increased
    • central area of low attenuation ± calcifications
    • peripheral enhancement

    MR:
    • lesion isointense to muscle on T1WI:
      • mildly T1-hyperintense center of myofibroma
    • lesion hyperintense to muscle on T2WI
    • intense occasionally targetlike enhancement

    DDx:
    1. Neurofibromatosis
    2. Infantile fibrosarcoma, leiomyosarcoma
    3. Angiomatosis
  • Lung
    • interstitial fibrosis, reticulonodular infiltrates
    • discrete mass
    • generalized bronchopneumonia
  • GI tract
    • diffuse narrowing / multiple small filling defects
  • Orbit

Aggressive Infantile Fibromatosis  !!navigator!!

= childhood equivalent of deep fibromatosis

Age: first 2 years of life; rarely >5 years of age; M >F

Histo: may mimic infantile fibrosarcoma

  • firm nodular soft-tissue mass within skeletal muscle / fascia / periosteum

Location: head, neck (tongue, mandible, mastoid), shoulder, thigh, foot

 Outline