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Information

 Bone and Soft-Tissue Disorders

Benign Fibrous Histiocytoma  !!navigator!!

Frequency: 0.1% of all bone tumors

Histo: interlacing bundles of fibrous tissue in storiform pattern (whorled / woven) interspersed with mono- / multinucleated cells resembling histiocytes, benign giant cells, and lipid-laden macrophages; resembles nonossifying fibroma / fibroxanthoma

Age: 23–60 years

  • localized intermittently painful soft-tissue swelling

Location: long bone, pelvis, vertebra (rare)

Site: typically in epiphysis / epiphyseal equivalent

  • well-defined radiolucent lesion with septa / soap-bubble appearance / no definable matrix
  • may have reactive sclerotic rim
  • narrow transition zone (= nonaggressive lesion)
  • no periosteal reaction

Rx: curettage

DDx: nonossifying fibroma (childhood / adolescence, asymptomatic, eccentric metaphyseal location)

Atypical Benign Fibrous Histiocytoma  !!navigator!!

Histo: “atypical aggressive” features = mitotic figures present

  • lytic defect with irregular edges

Prognosis: may metastasize

Malignant Fibrous Histiocytoma  !!navigator!!

= MFH = Undifferentiated pleomorphic sarcoma = Malignant fibrous xanthoma = XANTHOSARCOMA = MALIGNANT HISTIOCYTOMA = FIBROSARCOMA VARIANT

Histo: spindle-cell neoplasm of a mixture of fibroblasts + giant cells resembling histiocytes with nuclear atypia and pleomorphism in pinwheel arrangement; closely resembles high-grade fibrosarcoma (= fibroblastic cells arranged in uniform pattern separated by collagen fibers)

  1. pleomorphic-storiform subtype (50–60%)
  2. myxoid subtype (25%)
  3. giant cell subtype (5–10%)
  4. inflammatory subtype (5–10%)
  5. angiomatoid subtype (<5%)

Mean age: 50 (range, 10–90) years; peak prevalence in 5th decade; more frequent in Caucasians; M÷F = 3÷2

Location: potential to arise in any organ (ubiquitous mesenchymal tissue); soft tissues >>bone

Soft-tissue MFH

Frequency: 20–24–30% of all soft-tissue sarcomas; most common primary malignant soft-tissue tumor of late adult life

◊Any deep-seated invasive intramuscular mass in a patient >50 years of age is most likely MFH!

  • large painless lobulated soft-tissue mass with progressive enlargement over several months

Location: extremities (75%), [lower extremity (50%), upper extremity (25%)], retroperitoneum (15%), head + neck (5%); subcutis (7–10%)

Site: within large muscle groups

Size: usually 5–10 cm → increasing over months / years

  • poorly defined curvilinear / punctate peripheral calcifications / ossifications (in 5–20%)
  • commonly cortical erosion of adjacent bone (HIGHLY SUGGESTIVE FEATURE)

CT:

  • well-defined large lobulated soft-tissue mass with attenuation similar to that of muscle
  • central hypodense area = myxoid MFH (DDx: hemorrhage, necrosis, leiomyosarcoma with necrosis, myxoid lipo- / chondrosarcoma)
  • enhancement of solid components
  • invasion of adjacent organs

MR:

  • inhomogeneous poorly defined lesion:
    • low to intermediate SI similar to muscle on T1WI
    • heterogeneously intermediate to high SI on T2WI
  • contrast enhancement more pronounced in periphery than at center ← central location of hemorrhage + necrosis + myxoid tumor component:
    • myxoid tumor component similar to fluid
    • nodular + peripheral enhancement of nonmyxomatous cellular region

Prognosis: larger + more deeply located tumors have a worse prognosis; 2-year survival rate of 60%; 5-year survival rate of 50%; local recurrence rate of 19–31%; metastatic rate of 31–35% (lung [90%], bone [8%], liver [1%], lymph nodes [4–17%])

DDx:

  1. Liposarcoma (younger patient, presence of fat in >40%, calcifications rare)
  2. Rhabdomyosarcoma
  3. Synovial sarcoma (cortical erosion)

Osseous MFH

Prevalence: 5% of all primary malignant bone tumors

  • painful, tender, rapidly enlarging mass
  • pathologic fracture (20%)

Associated with:

  • prior radiation therapy, bone infarcts, Paget disease, fibrous dysplasia, osteonecrosis, fibroxanthoma (= nonossifying fibroma), enchondroma, chronic osteomyelitis
    • 20% of osseous MFH arise in areas of abnormal bone!

Location: femur (45%), tibia (20%), 50% about knee; humerus (10%); ilium (10%); spine; sternum; clavicle; rarely small bones of hand + feet

Site: central metaphysis of long bones (90%); eccentric in diaphysis of long bones (10%)

Size: 2.5–10 cm in diameter

  • radiolucent defect with ill-defined margins
  • extensive mineralization / small areas of focal metaplastic calcification
  • permeation + cortical destruction
  • expansion in smaller bones (ribs, sternum, fibula, clavicle)
  • occasionally lamellated periosteal reaction (especially in presence of pathologic fracture)
  • soft-tissue extension

Cx: pathologic fracture (30–50%)

DDx:

  1. Metastasis
  2. Fibrosarcoma (often with sequestrum)
  3. Reticulum cell sarcoma
  4. Osteosarcoma
  5. Giant cell tumor
  6. Plasmacytoma

Pulmonary MFH (extremely rare)

  • solitary pulmonary nodule without calcification
  • diffuse infiltrate

NUC:

  • increased uptake of 99mTc-MDP (mechanism not understood)
  • increased uptake of 67Ga-citrate

US:

  • well-defined mass with hyperechoic + hypoechoic (necrotic) areas

CT:

  • mass of muscle density with hypodense areas (necrosis)
  • invasion of abdominal musculature, but not IVC / renal veins (DDx to renal cell carcinoma)

Angio:

  • hypervascularity + early venous return

 Outline