CASE 33
By: Dr. Waleed Althobaity, MD
HISTORY: 14-year-old male with left knee swelling.
What are your findings?
What is the deferential diagnosis?
What is your diagnosis?
What is the next step?
FINDINGS:
Anteroposterior(A) and lateral (B) radiographs of the left knee show sclerotic lesion affecting distal meta-diaphysis of the femur, associated with destruction of the cortex, aggressive periosteal reaction, and a soft-tissue mass. There is additional sclerotic lesion at proximal diaphysis of femur which represent a skip lesion.
DIFFRENTIAL DIAGNOSIS:
Osteosarcoma.
Ewing sarcoma.
DIAGNOSIS:
Osteosarcoma (Conventional Type) With Skipped Lesion.
Next Step:
Orthopedic oncology referral and tumor workup including MRI (for local staging), bone scan and chest X-ray +/- low dose CT-scan of chest.
PEARLS AND DISCUSSION:
Conventional osteosarcoma is primary intramedullary high-grade malignant sarcoma in which neoplastic cells produce osteoid or bone. Most common primary nonhematopoietic malignancy of bone. Most common in second decade of life with 60% of tumors in patients younger than 25 years. About 30% occur in patients over 40 years of age (predisposing conditions include radiation therapy and Paget disease of bone). Osteosarcoma most commonly involves long bones of the appendicular skeleton with preference to the distal femur, proximal tibia, and proximal humerus. Most of the tumors are centered in metaphysis of long bones (90%), followed by diaphysis (9%), and rarely epiphysis.
Conventional tumors usually present as a large, destructive, poorly defined, mixed lytic and blastic lesions exhibiting wide zone of transition and moth-eaten bone destruction, accompanied by cortical invasion and extension into the soft tissues with periosteal reactive bone formation. Periosteal reaction such as Codman triangle, perpendicular or radiating coarse striations (“sunburst” periosteal reaction), or less common lamellated periosteal layers (onion skin type of periosteal reaction).
In contrast to osteosarcoma, Ewing sarcoma location is usually in diaphysis. Permeative type of bone destruction more common. Usually there is lack of mineralization of the matrix. Onion skin (lamellated) type of periosteal reaction is more common than sunburst. Some time, there will be soft-tissue mass disproportionally larger in comparison to the osseous involvement.
FURTHER READINGS:
Greenspan, Adam; Borys, Dariusz (2015-09-21). Radiology and Pathology Correlation of Bone Tumors: A Quick Reference and Review (Kindle Locations 1607-1609). LWW. Kindle Edition.
