MSK: Agressive Lesions Flashcards
What are the most common primary osseous malignancies?
- Myeloma/plasmacytoma (27%)
- Osteosarcoma (20%)
- Chondrosarcoma (20%)
What is the best sign that an osseous lesion is aggressive?
A wide zone of transition (you can’t trace the edges of the lesion with a pencil)
Note: This indicates that the lesion is too fast for the bone to be able to create a sclerotic border around it.
Arrow
Codman triangle, indicating a very aggressive lesion
Note: The lesion grew so fast it burst out of the cortex, leaving the Codman triangle pushed away.
Arrow
Codman triangle, indicating that this is a Pathologic fracture due to a very aggressive lesion
What are the major subtypes of osteosarcoma?
- Intramedullary (85%)
- Parosteal (4%)
- Periosteal (1%)
- Telangiectatic (rare)
Common etiologies for osteosarcoma
- Idiopathic (most common)
- Radiation therapy
- Pagets
- Infarctions
Osteosarcoma is more common in what pt population?
Young pts (10-20 years)
What are the most common locations for osteosarcoma?
- Femur (40%)
- Proximal tibia (15%)
What type of periosteal reactions are suspicious for osteosarcoma?
- Subburst
- Lamellated
- Codman triangle
- Reverse zoning phenomenon
What is the classic cause of occult pneumothorax?
Osteosarcoma metastasis to the lung
Think osteosarcoma
Note: Sunburst periosteal reaction in the femur.
Why is it important to image the entire bone that contains an osteosarcoma?
Skip metastases occur in 5% of cases (usually proximal to the primary tumor)
Note: A bone scan is usually done during staging also for this reason.
What imaging studies are usually performed during osteosarcoma staging?
- Bone scan (monoostotic vs polyostotic)
- Chest CT (to look for lung mets)
- MRI of the entire involved bone (to look for skip lesions and plan biopsy)
When does osteosarcoma recurrence usually occur?
Within 2 years of surgical resection
What is the most common location for osteosarcoma relapse?
Lung (80%)
Note: Bone relapse occurs less frequently (20%).
Why is a second biopsy usually done following Neoadjuvant chemotherapy for osteosarcoma?
To predict outcome
Note: 90% tumor death is a good prognostic feature.
What is the classic location for a parosteal osteosarcoma?
Posterior distal femur metaphysis
Think parosteal osteosarcoma
Note: Posterior distal femur metaphysis is a common location.
Reverse zoning phenomenon…
Think osteosarcoma
Note: This is when you have soft tissue calcification with a denser matrix in the center and less dense matrix peripherally (the opposite of myositis ossificans).
Are parosteal osteosarcomas usually lower or higher grade?
Low grade (typically the lowest grade of all the subtypes of osteosarcoma)
Arrows
String sign, suspicious for parosteal osteosarcoma
Note: The radiolucent string separates the bulky tumor from the cortex.
List the major subtypes of osteosarcoma from best prognosis to worst prognosis
What is the classic location for a periosteal osteosarcoma?
Medial distal femur diaphysis
Think periosteal osteosarcoma
Note: Broad-based cortically attached tumor with aggressive, lamellated/Codman’s triangle periosteal reaction and associated partially mineralized soft tissue mass.
What are the two subtypes of surface osteosarcoma?
- ParOsteal (Outer layer of periosteum)
- PerIosteal (Inner layer of periosteum)
Which subtype of surface osteosarcoma often has marrow extension?
Parosteal (50%)
Note: Periosteal osteosarcomas usually do not have marrow extension.
What is the classic imaging finding for telangiectatic osteosarcoma?
Fluid-fluid levels
Differential for osseous lesion with fluid-fluid levels
- Telangiectatic osteosarcoma
- Aneurysmal bone cyst
- Giant cell tumor
Note: Telangiectatic osteosarcoma should be more nodular and enhancing than the others.
Permeative lesion in the diaphysis of a pediatric pt…
Think Ewings sarcoma
Note: Infection and eosinophilic granuloma can also look like this.
Where do Ewing sarcomas usually metastasize to?
- Bone (most common, often to the spine)
- Lung
Note: Ewings is the most likely sarcoma to metastasize to another bone (often appears polyostotic).
Is it common to have a soft tissue component in Ewings sarcoma?
Yes (80%), most commonly to the spine
Note: Unlike for osteosarcoma, the soft tissue component rarely has calcification.
What is the most common location for Ewings sarcoma?
Femoral diaphysis
Pediatric pt
Think Ewing sarcoma
Note: Permeative/moth-eaten lesion in the femoral diaphysis of a pediatric pt.
Ewings sarcoma is more common in what pt population?
Pediatric (~15 y/o)
Chondrosarcoma is usually seen in what pts?
Older adult males (40-70 y/o)
What is the most common location for chondrosarcoma?
Distal femur
Note: Chondrosarcoma is more common in proximal tubular bones and limb girdles (e.g. triradiate cartilage in pelvis) due to more abundant cartilage.
What is the most common location for chondrosarcoma metastases?
Lung
Note: Bone is second most common.
Chondroblastoma in an adult…
Think clear cell chondrosarcoma
What are the main aggressive osseous lesions?
- Osteosarcoma
- Ewings sarcoma
- Chondrosarcoma
- Chordoma
Risk factors for chondrosarcoma
- Pagets
- Cartilaginous disorders (e.g. osteochondromas, Maffucci, etc.)
What type of matrix does this tumor have?
Chondroid
Note: Rings and arcs.
What features should make you suspicious of a chondrosarcoma rather than an enchondroma?
- Pain
- Cortical destruction
- Scalloping of > 2/3 of the cortex
- Size > 5cm
- Changing matrix
What is the typical age group for chordomas?
30-60 y/o
What is the most common location for a chordoma?
- Sacrum (most common)
- Clivus
- Vertebral body
What is the classic imaging feature of a chordoma?
Very T2 bright
Chordomas can be seen in different locations, but they will ALWAYS be…
Midline
Note: This is because it derived from a notochord remnant.
What is the most common primary malignancy of the spine?
Chordoma
What is the most common primary malignancy of the sacrum?
Chordoma
What is the most common spinal location for a chordoma?
C2
