Osteosarcoma vs Ewing sarcoma, chondrosarcoma, and osteoid osteoma
How to tell Osteosarcoma and Ewing sarcoma, chondrosarcoma, and osteoid osteoma apart when a board question makes them look alike.
Osteosarcoma is metaphyseal osteoid sunburst; Ewing is diaphyseal onion-skin t(11;22); chondrosarcoma is older cartilage pelvis; osteoid osteoma is night pain relieved by NSAIDs.
Side by side
Osteosarcoma occurs in adolescents near metaphyses around the knee or in older Paget/radiation patients, with sunburst periosteal reaction and Codman triangle.
Ewing is a diaphyseal small round blue cell tumor with onion-skin periosteum and t(11;22); chondrosarcoma is older pelvic cartilage tumor; osteoid osteoma is nocturnal NSAID-responsive pain.
Malignant osteoblasts produce osteoid matrix, classically creating an aggressive metaphyseal bone tumor with periosteal elevation.
Ewing arises from primitive neuroectodermal cells; chondrosarcoma produces cartilage; osteoid osteoma is a benign prostaglandin-producing nidus.
Osteoid-producing malignant cells, metaphyseal lesion, sunburst pattern, and Codman triangle support osteosarcoma.
CD99 and t(11;22) support Ewing; malignant cartilage supports chondrosarcoma; small nidus relieved by NSAIDs supports osteoid osteoma.
The trap
Bone tumors overlap by pain, so age, site, matrix, x-ray pattern, and molecular clue separate them.
The repair move
For bone tumors, pair age, location, and X-ray pattern before naming the lesion: (1) METAPHYSEAL location (distal femur, proximal tibia, proximal humerus) in an ADOLESCENT or young adult plus Codman triangle plus sunburst periosteal reaction plus osteoid production on biopsy equals osteosarcoma (associated with Paget disease in the elderly second peak and with prior retinoblastoma; treat with neoadjuvant chemotherapy plus limb-sparing surgery); (2) DIAPHYSEAL location in a CHILD or young adult plus onion-skin periosteal reaction plus small round blue cells with CD99 positivity plus t(11;22) EWS-FLI1 fusion equals Ewing sarcoma (treat with multimodal chemotherapy plus radiation plus surgery); (3) older adult (40 to 60 plus) plus pelvis or proximal femur or humerus plus popcorn or punctate calcifications plus malignant cartilage on biopsy equals chondrosarcoma; (4) young adult plus painful lesion WORST AT NIGHT plus complete pain relief with aspirin or NSAIDs plus small central nidus under 2 cm with surrounding sclerosis on X-ray equals osteoid osteoma (benign; treat with NSAIDs or radiofrequency ablation).
Try a free question
CoreA 14-year-old boy has 3 weeks of progressive pain and swelling above his right knee. X-ray shows a metaphyseal lesion of the distal femur with sunburst periosteal reaction and Codman triangle. Biopsy reveals malignant pleomorphic cells producing osteoid. Which diagnosis is most likely?
Show answer and explanation
Answer: A. Osteosarcoma. Osteosarcoma is the most common primary malignant bone tumor in adolescents, classically at the metaphysis of long bones around the knee, with sunburst periosteal reaction, Codman triangle, and malignant osteoid-producing cells; treatment is neoadjuvant chemotherapy plus limb-sparing surgery.
Why the other choices are tempting
- B. Ewing sarcoma is diaphyseal with onion-skin periosteal reaction and t(11;22) EWS-FLI1 translocation.
- C. Chondrosarcoma occurs in older adults in the pelvis/proximal femur with cartilage matrix.
- D. Osteoid osteoma is benign with night pain dramatically relieved by NSAIDs and a small central nidus on imaging.
- E. Giant cell tumor occurs at the epiphysis of young adults (post-physeal closure) with soap-bubble lytic appearance.
Flashcards
Tap a card to flip it.
What x-ray pattern supports osteosarcoma?
Sunburst periosteal reaction or Codman triangle supports osteosarcoma.
What translocation supports Ewing sarcoma?
t(11;22) supports Ewing sarcoma, especially a diaphyseal small round blue cell tumor with onion-skin periosteum.
Quick answers
What is the fastest way to tell Osteosarcoma from Ewing sarcoma, chondrosarcoma, and osteoid osteoma?
Osteosarcoma is metaphyseal osteoid sunburst; Ewing is diaphyseal onion-skin t(11;22); chondrosarcoma is older cartilage pelvis; osteoid osteoma is night pain relieved by NSAIDs.
What is the key clue for Osteosarcoma?
Osteosarcoma occurs in adolescents near metaphyses around the knee or in older Paget/radiation patients, with sunburst periosteal reaction and Codman triangle.
What is the key clue for Ewing sarcoma, chondrosarcoma, and osteoid osteoma?
Ewing is a diaphyseal small round blue cell tumor with onion-skin periosteum and t(11;22); chondrosarcoma is older pelvic cartilage tumor; osteoid osteoma is nocturnal NSAID-responsive pain.
What is the common trap with Osteosarcoma vs Ewing sarcoma, chondrosarcoma, and osteoid osteoma?
Bone tumors overlap by pain, so age, site, matrix, x-ray pattern, and molecular clue separate them.