dr james c wittig, orthopedic oncologist, new york, new jersey
About Dr. Wittig
Low Grade Intraosseous Osteosarcoma

GENERAL INFORMATION

Low Grade Intraosseous Osteosarcoma is a low grade malignant bone tumor that accounts for 1% to 2% of all Osteosarcomas. Constituent cells of the tumor form osteoid or immature woven bone. 

CLINICAL DATA

 More frequent in second and third decades of life. 
 Long bones are the most frequent location (80%) 
 Tumors most commonly arise around the knee 
 Patients commonly present with pain and perhaps an enlarging soft-tissue mass 

Differential Diagnosis
 Fibrous dysplasia
• Low-grade fibrosarcomas
• Parosteal osteosarcoma
• Other benign lucent lesions such as osteoblastoma, chondroblastoma, giant cell tumor and non ossifying fibroma depending on location

RADIOGRAPHIC PRESENTATION

Plain x-ray
 Radiographs of low grade intraosseous osteosarcoma may demonstrate a benign appearance (Fig. 1 & 2).
• However, most lesions show intramedullary extension, cortical violation, and soft tissue involvement.
• The majority arise centrally in the bone, from the medullary cavity and more frequently are methaphyseal. 

MRI
 MR Imaging, demonstrates intermediate to hypointense signal on T1-weighted images (Fig. 4 & 5) and hyperintensity on T2-weighted images (Fig. 6 & 7).
• Most cases show an extraosseous mass and cortical disruption on MRI. 
• Bone scintigraphy frequently display an increase radiotracer uptake (Fig. 8).


Fig. 1


Fig. 2

Fig. 1 & 2: Plain X Ray of Low Grade Intraosseous Osteosarcoma. AP (Fig. 1) and Lateral (Fig. 2) view of the left knee, shows a mixed sclerotic-lytic lesion in the supracondylar area of the femur. There is no periosteal reaction, cortical destruction, or extraosseous soft tissue mass. The lesion is fairly well circumscribed with a sclerotic margin. The lesion deceptively looks benign


Fig. 3: CT Scan of the left knee showing a lytic lesion within the lateral supracondylar femur with surrounding sclerosis.  No definite osseous or cartilaginous matrix was seen.


Fig. 4


Fig. 5

Fig. 4 & 5:  MR Imaging. Axial (Fig. 4) and Coronal (Fig. 5) T1 weighted image demonstrates a well-defined T1 hypointense mass within the femur with a more hypointense border corresponding to the sclerosis noted on the CT


Fig. 6


Fig. 7

Fig. 6 & 7: MR Imaging. Axial (Fig. 6) and Coronal (Fig. 7) T2 fat saturated image demonstrating T2 hyperintense lesion within the lateral supracondylar femur with a small amount of surrounding bone marrow edema.


Fig. 8: Bone scintigraphy. Anterior and lateral bone demonstrates increased radiotracer uptake in the left lateral supracondylar femur.

PATHOLOGY

Low Grade Intraosseous Osteosarcoma is a low-grade malignancy, similar to parosteal osteosarcoma.

Microscopic
• Display bundles of spindle cell proliferations with variable osteoid production, low cellularity, low mitotic rate, and minimal pleomorphism (Fig. 9 & 10).
• The presence of infiltrative margins and the absence of marked cellular atypia helps to differentiate low grade intraosseous osteosarcoma from benign entities.


Fig. 9


Fig. 10

Fig. 9 & 10: Microscopic Pathology. Low and high power views with irregular woven bone trabeculae in a moderately cellular fibrous tissue. Atypical cells displaying hyperchromatic nuclei are closely associated with the irregular woven bone trabeculae.

TREATMENT

• Treatment is the same for parosteal osteosarcoma.
• Radical / wide resection is the mainstay of treatment.
• Chemotherapy and radiation are usually not indicated as long as the tumor is entirely low grade.
• Rarely, Low grade Intraosseous Osteosarcoma progress to high grade sarcomas.


Fig. 11
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