Bone Tumors
Dedifferentiated Chondrosarcoma

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James C. Wittig, MD
Sarcoma Surgeon
Orthopedic Oncologist

Dedifferentiated chondrosarcoma consists of a low grade malignant hyaline cartilage tumor associated with a high-grade nonchondroid spindle sarcoma. The two components are juxtaposed with abrupt clear demarcation line
     The high grade sarcoma is most commonly an MFH, osteosarcoma or fibrosarcoma although 
     others may occur
     It is an extremely aggressive tumor with a high metastatic rate and dismal prognosis
     Constitutes approximately 10% of chondrosarcomas
     50% arise from a secondary chondrosarcoma

Radiology emulates pathology: Biphasic Tumor
     One region low grade chondrosarcoma
     Second more aggressive area with bone destruction, lysis of calcification, soft tissue mass
     Cortical permeation and a soft tissue mass in 70% of cases

Ill-defined, lytic intraosseous lesion
     Or extraosseous soft tissue mass
     Devoid of calcifications
           in continuity with lesions having the features of a cartilaginous tumor

Characteristically abrupt transition between chondroid tumor and dedifferentiated, lytic component

Bone may be expanded and adjacent cortex thickened

Plain X-Ray:
Dedifferentiated Chondrosarcoma of Proximal Tibia

Low Grade Cartilaginous Area Heavily Calcified

Aggressive Lytic Area (Dedifferentiated Sarcomatous Component) Cortical Destruction Soft Tissue Mass without Calcification

Plain X-ray:
Dedifferentiated Chondrosarcoma of Humerus

Low Grade Cartilage Component Stippled Calcifications Aggressive Dedifferentiated Sarcomatour Component Lysis, Cortical Destruction Soft Tissue Mass without Calcification

Plain X-ray/CT:
Dedifferentiated Chondrosarcoma of Proximal Humerus 

Lytic, Dedifferentiated Component   Low Grade Cartilage Component Heavily Calcified

Soft Tissue Extension on CT     Ring and Arc Calcifications

Plain Xray:
Dedifferentiated Chondrosarcoma of Acetabulum 

Ring and Arc Calcification	Lysis, Dedifferentiated Component

Bone Scan:
Increased Uptake in Dedifferentiated
Chondrosarcoma of Left Acetabulum

CT and MRI:
Dedifferentiated Chondrosarcoma of Left Acetabulum


Soft Tissue Extension

Plain X-ray:
Dedifferentiated Chondrosarcoma
of Proximal Femur

Cortical Thickening	High Grade, Lytic Dedifferentiated Sarcoma Component Cortical Destruction Soft Tissue Extension
Heavily Mineralized Low Grade Cartilage Component

CT Scan:
Dedifferentiated Chondrosarcoma of Proximal Femur

Chondroid Calcification	Cortical Destruction and Soft Tissue Extension

MRI:
Dedifferentiated Chondrosarcoma of Proximal Femur

TI Weighted Image Cortical Destruction and Soft Tissue Extension

T2 Weighted Image

MRI:
Dedifferentiated Chondrosarcoma of Proximal Femur

X-ray and CT Scan:
Dedifferentiated Chondrosarcoma of Scapula

Large Soft Tissue Mass from Scapula Calcifications

Dedifferentiated Chondrosarcoma of Distal Femur with Minimal Cortical
Destruction and Soft Tissue Extension (Very Rare Presentation)

Heavily Calcified Low Grade Component Destruction

Minimal Cortical Destruction

MRI: Dedifferentiated Chondrosarcoma of Distal Femur with Minimal Cortical Destruction and Soft Tissue Extension (Very Rare Presentation)

Bone Scan: Dedifferentiated Chondrosarcoma of Distal Femur
Intense Uptake on Bone Scan

Areas with typical lobular, blue-gray myxoid hyaline cartilage tissue
      Or overtly cartilaginous appearance of mature hyaline cartilage
Zones of brown, tan, or hemorrhagic tissue
      Lacking the consistency of cartilage
Dedifferentiated component may only be a minor portion of the overall tumor
May also be so extensive that little cartilage is recognizable

Dedifferentiaed Chondrosarcoma of Distal Humerus

Low Grade                      & Dedifferentiated Component
Cartilage Componenet

Low Grade Cartilage     High Grade Dedifferentiated Specimen Component

Chondrosarcoma component is often grade I (Low Grade Hyaline Type Cartilage)
Dedifferentiated component
      Predominant noncartilaginous/spindle sarcoma component varies
          Fibrosarcoma and MFH most frequently reported
               MFH is a high grade pleomorphic spindle cell tumor with a storiform pattern
     Osteosarcoma is third most common dedifferentiated component
     Rhabdomyosarcoma and angiosarcoma also reported

Junction of cartilaginous and noncartilaginous components is sharp and distinct. There are no dedifferentiated areas admixed in the middle of the cartilaginous areas

	Malignant Spindle                Low Grade Cartilage Cell Component                  Component

High Grade Dedifferentiated Spindle Cell Sarcoma Component   Low Grade Cartilage Component

Microscopic Pathology:
Dedifferentiated Chondrosarcoma

Low Grade Cartilage          High Grade Malignant
Component                        Spindle Cell Component

Microscopic Pathology:
Dedifferentiated Chondrosarcoma

Low Grade Cartilage                          Dedifferentiated Component
Component

Microscopic Pathology: 
Dedifferentiated Chondrosarcoma

Low Grade Cartilage               Dedifferentiated Component
Component

Dedifferentiated Chondrosarcoma:  High PowerView of Dedifferentiated High Grade Pleomorphic Spindle Cell Component

Malignant Fibrous Histiocytoma with Storiform Pattern

High Grade Chondrosarcoma with Spindle Cell Areas
Mesenchymal Chondrosarcoma
Chondroblastic Osteosarcoma
Malignant Fibrous Histiocytoma
Fibrosarcoma

Very aggressive locally
     Frequently cortical perforation
     Mass is usually large if extraosseous extension occurs
Extremely high metastatic rate
     Metastasizes primarily to lungs
     Also bones and other organs

Wide/Radical limb sparing resection whenever feasible
Amputation may be necessary for large tumors
Chemotherapy may be considered for high grade dedifferentiated component but is controversial and no clear cut benefit has ever been demonstrated
Radiation may be considered if the tumor is unresectable or if a wide margin can not be achieved with surgery such as with large pelvic tumors. Radiation would be used as an adjuvant to eradicate any residual microscopic disease.
Prognosis almost hopeless, regardless of extent of resection
          90% of patients are dead of metastatic disease within 2 years
               Most of these die within 1 year
         Metastases consist solely of high-grade dedifferentiated component
               Predominantly in lungs
               Also bones and other organs