Age / Sex : 52 / F

Low grade osteosarcoma

Discussion

Findings:

 Radiographs show a focal area of moderately dense sclerotic matrix within a predominantly osteolytic lesion in the proximal tibial metadiaphysis. CT and MRI demonstrate anteromedial tibial cortical destruction and a soft tissue mass. No periosteal reaction is present.

Pathologic report:

 Bone, tibia, left, wide excision;

1. Primary tumor diagnosis; Sclerotic osteosarcoma, low grade


2. Tumor site; Metaphysis, medullary cavity, Tumor extension into soft tissue


3. Tumor size; 4.5x1.5cm


4. Pathologic staging (pT); Tumor 8cm or less in greatest dimension (pT1)


5. Margins; Free from tumor, Distance of sarcoma from closest margin: proximal; 2.1cm, distal; 2.4cm


6. Lymph-vascular invasion; Not identified


7. Neural invasion; Not identified


8. Preresection treatment; No therapy

 Diagnosis:  

Low grade osteosarcoma

Discussion:

 Low grade osteosarcoma is an uncommon subtype of osteosarcoma accounting less than 1% of all osteosarcomas. Low grade osteosarcoma affects individuals of higher age group as compare to the other subtypes of osteosarcoma. The usual age of presentation is 19 to 54 years with the mean age of 33 years. It shows slight female predilection. Histologically it is a low grade tumor which occurs in medullary canal of long bones. It contains osseous matrix with blend fibrous stroma and there is variable amount of bone production. Histologic pattern is similar to fibrous dysplasia and low grade parosteal osteosarcoma. Most commonly (85%) occurs in the metaphysis or diametaphysis of distal femur followed by proximal tibia. Less commonly (15%) it can be found in flat bones.

Radiographic features of low-grade central osteosarcoma are variable. The most common radiographic appearance is expansile lytic bone destruction with coarsely thick or thin incomplete trabeculation. A dense sclerotic pattern is less common. Cortical disruption and soft-tissue extension are common at CT and MR imaging. Variable rates of periosteal reaction (22%–50%) at radiography are also reported. Differential radiologic diagnoses include benign fibro-osseous lesions such as fibrous dysplasia, nonossifying fibroma, and desmoplastic fibroma.

References:

1. Arslan HS, Aydin O, Dervışoğlu S et-al. Low-grade osteosarcoma, review of 15 cases in a series of 156 osteosarcoma cases. Turk Patoloji Derg. 2011;27 (2): 138-43.


2. Yarmish G, Klein MJ, Landa J et-al. Imaging characteristics of primary osteosarcoma: nonconventional subtypes. Radiographics. 2010;30 (6): 1653-72.


3. Andresen KJ, Sundaram M, Unni KK et-al. Imaging features of low-grade central osteosarcoma of the long bones and pelvis. Skeletal Radiol. 2004;33 (7): 373-9.