Bone and Soft Tissue Tumors

Question 1

• What is osteosarcoma?
• Who does it usually affect and what are the risk factors ?

Answer 1

• Malignant proliferation of osteoblast
• Peak incidence seen in:
  
  • teenagers
    
    • familial retinoblastoma
  • elderly (less common)
    
    • Paget disease
    • radiation exposure

Question 2

• Where does osteosarcoma usually arise?
• What does it present as?

Answer 2

• Arise in metaphysis of long bone
  
  • usually distal femur or proximal tibia (region of knee)
• Present as pathological fracture or bone pain with swelling
  
  • tumor weakens bone

Question 3

What does x-ray imaging of osteosarcoma show?

Answer 3

• Destructive mass with “sunburts” appearance
• Lifting of the periosteum (Codman triangle)
  
  • as tumor grows out into tissue it tears at the periosteum

Question 4

What does biopsy of osteosarcoma show?

Answer 4

Pleomorphic cells that produce osteoid

Question 5

• Osteochondroma is what kind of tumor?

Answer 5

• Tumor of the bone with an overlying cartilage cap
  
  • most common benign tumor of bone

Question 6

• What does osteochondroma arise from?
• What can it transform to?

Answer 6

• Arises from a lateral projection of the growth plate (metaphysis)
  
  • ​cartilage capped tumor that is attached to underlying skeleton by a bony stalk
  • bone is continuous with the marrow space
  • Especially near the knee
• Overlying cartilage can transform to chondrosarcoma (rare)

Question 7

• ​What are chondromas?
• Who do they usually affect?
• Where do they usually arise?

Answer 7

• Benign tumor of cartilage
• Affect 20-50 years of age
• Usually arise in the medulla of small bones of the hand and feet

Question 8

• What is chondrosarcoma?
• Where does it typically arise?

Answer 8

• Malignant cartilage forming tumor
• Arises in medulla of the pelvis or central skeleton

Question 9

• Ewing sarcoma is what kind of proliferation?
• Where are cells derived from?
• Where does it arise and who does it affect?

Answer 9

• Malignant proliferation of poorly differentiated cells
  
  • arise from neuroectoderm
• Arise in diaphysis of long bone
  
  • usually in male children (< 15 yrs)

Question 10

• What mutation does Ewing sarcoma have?

Answer 10

• t (11;22)

Question 11

• What appearance does Ewing sarcoma have on x-ray?
• Why?

Answer 11

• “onion skin” appearance
  
  • tumor grows inside medullary cavity
  • pushes on the bone and pressure on periosteum causes it to lay down layers of new bone

Question 12

• What does biopsy of Ewing Sarcoma show?
• What can it be confused with?
  
  • how to differentiate?

Answer 12

• Biopsy reveals small round blue cells that resemble lyphocytes
• Can be confused with lymphoma or chronic osteomyelitits
  
  • ONLY Ewing sarcoma has t (11;22)

Question 13

• Giant cell tumor (or osteoclastoma) are tumors comprised of?
• Who does it affect?
• Where does it arise?

Answer 13

• Multinucleated giant cells and stromal cells
• Occurs in young adults
• Arise in the epiphysis of long bones (ONLY ONE!)
  
  • usually the distal femur or proximal tibia (region of knee)
• Locally agressive but responds well to treatment

Question 14

• What appearance does Giant cell tumor have on X-ray?

Answer 14

• “soap bubble”: in epiphysis
  
  • neoplastic cells are primitive osteoblast precursor
  • express high levels of RANKL which promote proliferation of osteoclast
    
    • result in localized but highly destructive resorption of bone matrix

Question 15

• Aneurysmal bone cyst is what kind of tumor?
• Who does it affect and where?
• What does x-ray show?

Answer 15

• Benign tumor of bone
• occurs in first two decades of life
• Metaphysis of long bone
  
  • completely lytic on x-ray with thin shell of reactive bone at periphery

Question 16

• What is Fibrous dysplasia?
• Associated with what mutation?

Answer 16

• A benign tumor that has been likened to a localized developmental arrest
  
  • all of the components of normal bone are present but they don’t differentiate into mature structures
  • scar like fibrous tissue replaces bone; bone is weak
• GNAS1
  
  • gain of function mutation during development
  • promotes cell proliferation
• Occurs in early adolescence
  
  • stops enlarging at time of growth plate closure

Question 17

Describe each of the four types of fibrous dysplasia:

• Monostotic
• Polystotic
• Mazabraud syndrome
• McCune-Albright syndrome

Answer 17

Monostotic:

• involvement of a single bone

Polyostotic:

• involvement of mulitple bones

Mazabraud syndrome

• fibrous dysplasia (usually polyostotic) and soft tissue myxomas
• multiple skeletal deformities identified in childhood

McCune-Albright syndrome:

• polyostotic disease
• associated with cafe-au-lait skin pigmentation and endocrine abnormalities
  
  • epecially precrocious puberty (maturation during embryogenesis)

Question 18

• Plexiform neurofibromas can be found in deep or superficial locations associated with?
• Associated with what type of neurofibroma?

Answer 18

• in association with nerve roots or large nerves
  
  • not possible to separate tumor from the nerve
• associated with NF-1

Question 19

• What do tumor cells secrete that interact with bone cells?
• How can sclerotic metastases be produced by tumor cells?

Answer 19

• Secrete substances such as:
  
  • prostaglandins, cytokines, and PTHrP that upregulate RANKL on osteoblast and stromal cells
    
    • stimulate osteoclast activity
• Sclerotic metastases may be produced by tumor cells secreting WNT protein that stimulate osteoblastic formation

Question 20

• Schawnnomas are what kind of tumor?
• Associated with?

Answer 20

• encapsulated benign tumor
• associated with NF2

Question 21

• Malignant peripheral nerve sheath tumors can arise in what two ways?

Answer 21

1. Can be de novo sporadic neoplasms
2. NF1 associated tumors arising through malignant transformation of a (plexiform) neurofibroma