Bone and Soft-Tissue Disorders
- PRIMARY CHONDROSARCOMA
no preexisting bone lesion - SECONDARY CHONDROSARCOMA
= complication of a preexisting skeletal abnormality such as- Osteochondroma
- Enchondroma
- Parosteal chondroma
Spread: via marrow cavity / periosteum
Metastases (uncommon) to: lung, epidural space
May be associated with: Ollier disease, Maffucci syndrome, Paget disease
CT:
- chondroid matrix mineralization of “rings and arcs” (CHARACTERISTIC) in 70%
- nonmineralized portion of tumor hypodense to muscle (high water content of hyaline cartilage)
- extension into soft-tissues
MR:
- low to intermediate signal intensity on T1WI
- high SI on T2WI + hypointense areas ← mineralization / fibrous septa
- enhancement of fibrous septations
NUC:
- bone scan uptake intensity compared to anterior iliac crest: greater (82%) + equal to (12%) + less than (6%)
DDx: enchondroma; osteochondroma (marrow + cortical contiguity with cartilage cap); chordoma (calcification at periphery of lesion); chondroblastoma (lytic lesion with thin sclerotic margin; malignant fibrous histiocytoma; metastasis (history of primary tumor)
= INTRAMEDULLARY CHONDROSARCOMA = ENDOSTEAL CHONDROSARCOMA
Frequency: 3rd most common primary bone tumor (after multiple myeloma and osteosarcoma); 20–27% of all primary malignant neoplasms; 8–17% of biopsied primary bone tumors
Path: lobular morphology with variable amounts of calcium; presence of fibrous bands at tumor-marrow interface suggests malignancy (DDx from atypical enchondroma)
Histo: arises from chondroblasts (tumor osteoid never forms)
Age: median 45 years; 50% >40 years; 10% in children (rapidly fatal); M÷F = 2÷1
- hyperglycemia as paraneoplastic syndrome (85%)
Location: neck of femur, pubic rami, proximal humerus, ribs (19%), skull (sphenoid bone, cerebellopontine angle, mandible), sternum, spine (3–12%)
Site: central within medullary canal of meta- / diaphysis
- expansile osteolytic lesion 1 to several cm in size
- short transition zone ± sclerotic margin (well defined from host bone)
- ± small irregular punctate / snowflake type of calcification; single / multiple
- late: loss of definition + break through cortex:
- pathologic fracture (in 3–17% at initial presentation)
- endosteal cortical thickening, sometimes at a distance from the tumor ← invasion of haversian system
- presence of large soft-tissue mass
DDx: benign enchondroma, osteochondroma, osteosarcoma, fibrosarcoma
= EXOSTOTIC CHONDROSARCOMA
= malignant degeneration of hereditary multiple osteochondromatosis and rarely of a solitary exostosis (beginning in cartilaginous cap of exostosis)
Frequency: 8% of all chondrosarcomas
Average age: 50–55 years for solitary exostosis; 25–30 years for hereditary multiple osteochondromatosis; M÷F = 1.5÷1
Histo: low histologic grade in 67–85%
- growth after skeletal maturity
- gradually increasing pain, often worse at night
- local swelling / palpable mass (45%)
Location: pelvis, hip, scapula, sternum, ribs, ends of humerus / femur, craniofacial bones
- growth of a previously unchanged osteochondroma in a skeletally mature patient
- unusually large soft-tissue mass (= hyaline cartilage cap) containing flocculent / streaky chondroid calcifications (CHARACTERISTIC):
- cartilage cap 1.5–12 cm (average, 5.5–6 cm) thick
- >1.5 cm is suspect of malignant transformation
- cartilage cap 1.5–12 cm (average, 5.5–6 cm) thick
- irregular / indistinct lesion surface:
- dense radiopaque center with streaks radiating to periphery + loss of smooth margin
- focal regions of radiolucency in interior of lesion
- erosion / destruction of adjacent bone
Metastases: in 3–7%, most commonly to lung
Rx: wide resection
Prognosis: 70–90% long-term survival
DDx:
- Osteochondroma (densely calcified with multiple punctate calcifications)
- Parosteal osteosarcoma (more homogeneous density of calcified osteoid)
- Usually mistaken for chondroblastoma because of low grade malignancy (both tumors may be related)!
Histo: small lobules of tissue composed of cells with centrally filled vesicular nuclei surrounded by large clear cytoplasm
Age: 19–68 years, predominantly after epiphyseal fusion
Location: proximal femur, proximal humerus, proximal ulna, lamina vertebrae (5%); pubic ramus
Site: epiphysis
- single lobulated oval / round sharply marginated lesion of 1–2 cm in size
- surrounding increased bone density
- aggressive rapid growth to over 3 cm
- may contain calcifications
- bone often enlarged
- indistinguishable from conventional chondrosarcoma / chondroblastoma (slow growth over years)
Extraskeletal Myxoid Chondrosarcoma (most common)
Mean age: 50 years (range 4–92 years); M >F
Histo: surrounded by fibrous capsule + divided into multiple lobules by fibrous septa; delicate strands of small elongated chondroblasts suspended in an abundant myxoid matrix; rare foci of mature hyaline cartilage
- slowly growing soft-tissue mass; pain + tenderness (33%)
◊Metastatic in 40–45% at time of presentation!
Location: proximal extremities (thigh most common)
Site: deep soft tissues; subcutis (25%)
Size: usually between 4 and 7 cm in diameter
- lobulated soft-tissue mass WITHOUT calcification / ossification / cartilaginous differentiation
- usually ill-defined margins
- usually heterogeneous tumor ← necrosis + hemorrhage
MR:
- SI equal to muscle on T1WI + equal to fat on T2WI
- may mimic a cyst / myxoma
- rings + arcs on contrast-enhanced images ← lobulated growth pattern
Prognosis: 45% 10-year survival rate; 5–15 years survival after development of metastases
Extraskeletal Mesenchymal Chondrosarcoma
= MESENCHYMAL CHONDROSARCOMA
Frequency: 2–10% of all chondrosarcomas
- 50% of all mesenchymal chondrosarcomas arise in soft tissues
Histo: proliferation of small primitive mesenchymal cells with scattered islands of cartilage; hemangiopericytoma-like vascular pattern
Bimodal age distribution: M = F
- tumors of head + neck in 2nd–3rd decade (common): meninges, periorbital region
- tumors of thigh + trunk in 5th decade
- frequently metastasized to lungs + lymph nodes
- matrix mineralization (50–100%) characterized as rings + arcs / flocculent + stippled calcification / dense mineralization
MR:
- lobulated soft tissue mass with:
- low signal intensity on T1WI
- variable heterogeneous signal intensity on T2WI
- curvilinear / stippled areas of low signal intensity ← chondroid matrix calcifications
- complex heterogeneous enhancement
Prognosis: 25% 10-year survival rate
= extremely rare intraarticular malignant cartilaginous neoplasm
Etiology: ? de novo / metaplastic transformation of synovial osteochondromatosis
- Concurrent (and presumably preexistent) primary synovial chondromatosis in 50%
Age: 4th–7th decade
Histo: permeation of trabecular bone, spindle-shaped chondrocytes, myxoid change in cellular matrix, shift from normal cell clusters to sheets of tumor cells
- pain + muscle swelling / contracture in presence of a mass
Location: knee, hip, shoulder, smaller joints (rare)
Spread to: lung
- lobulated intraarticular soft-tissue mass:
- mass isointense on T1WI + hyperintense on T2WI
- calcified bodies of low SI on all pulse sequences
- CLASSIC juxtaarticular ring-and-arc pattern
- multiple nodules with peripheral enhancement
- features suggestive of malignancy:
- cortical bone erosion / destruction with marrow invasion
- widespread extraarticular extension of tumor beyond joint capsule
- hematogenous (to lung) / regional lymphatic metastases
DDx: synovial osteochondromatosis (indistinguishable with the exception that evidence of metastatic disease allows a definitive diagnosis)