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Presented by Edward McCarthy, M.D. and prepared by Maryam Farinola M.D.
Case 6: A 14-year-old man had pain in his knee for 6 months.
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Question 1 of 1
1. Question
Week 214: Case 6
A 14-year-old man had pain in his knee for 6 months. The radiograph demonstrated a poorly defined radiodense lesion in the distal femur metaphysis with cortical destruction./images/osteosarcoma 1.jpg
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/images/osteosarcoma 4.jpgCorrect
Answer: Osteosarcoma
Histology: Osteosarcoma is the most common primary malignant bone tumor and usually occurs in young adults and adolescents, as in this case. Histologically, sheets of atypical and pleomorphic sarcoma cells make pink seams of osteoid. This feature designates these cells as osteoblasts and the lesion, therefore, as an osteosarcoma. The radiograph in this case is diagnostic.
Discussion: The lesion is not an osteoblastoma. Osteoblastomas are well-defined lytic lesions. They manufacture abundant osteoid, but they are not composed of atypical and pleomorphic osteoblasts.
The lesion is not a malignant fibrous histiocytoma because of the extensive osteoid formation. Some osteoid osteogenic sarcomas may have a predominant histologic pattern of malignant fibrous histiocytoma, the presence of osteoid formation requires the diagnosis of osteosarcoma.
The lesion is not a parosteal osteosarcoma because parosteal osteosarcoma is entirely a surface lesion. This case involves the medullary canal of bone. Occasionally, a CT scan must be performed to see if the medually canal is involved when there is extensive soft tissue involvement with osteosarcoma. Moreover parosteal osteosarcomas are low-grade sarcomas and do not show severe pleomorphism.
Incorrect
Answer: Osteosarcoma
Histology: Osteosarcoma is the most common primary malignant bone tumor and usually occurs in young adults and adolescents, as in this case. Histologically, sheets of atypical and pleomorphic sarcoma cells make pink seams of osteoid. This feature designates these cells as osteoblasts and the lesion, therefore, as an osteosarcoma. The radiograph in this case is diagnostic.
Discussion: The lesion is not an osteoblastoma. Osteoblastomas are well-defined lytic lesions. They manufacture abundant osteoid, but they are not composed of atypical and pleomorphic osteoblasts.
The lesion is not a malignant fibrous histiocytoma because of the extensive osteoid formation. Some osteoid osteogenic sarcomas may have a predominant histologic pattern of malignant fibrous histiocytoma, the presence of osteoid formation requires the diagnosis of osteosarcoma.
The lesion is not a parosteal osteosarcoma because parosteal osteosarcoma is entirely a surface lesion. This case involves the medullary canal of bone. Occasionally, a CT scan must be performed to see if the medually canal is involved when there is extensive soft tissue involvement with osteosarcoma. Moreover parosteal osteosarcomas are low-grade sarcomas and do not show severe pleomorphism.
