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E1388. Osteosarcoma and Its Different Faces: What the Radiologist Needs to Know
Authors
  1. Candace Kim; Virginia Commonwealth University Medical Center
  2. Josephina Vossen; Virginia Commonwealth University Medical Center
  3. Peter Haar; Virginia Commonwealth University Medical Center
  4. Mauricio Jimenez; Virginia Commonwealth University Medical Center
Background
Background Information: Osteosarcoma is a primary malignant mesenchymal bone tumor with osteoid formation. It accounts for 20% of bone cancers and is the most common primary osseous malignancy excluding malignant neoplasms of marrow origin (myeloma, lymphoma and leukemia). Usually affects the long bones of the extremities (most common around the knee) in young patients (10-20 years). Most cases (75%) occur before the age of 20 because the growth centers of the bone are more active. Osteosarcomas are classified as primary (central or surface) and secondary osteosarcomas arising in preexisting conditions. Purpose: 1. The aim of this exhibit is to provide an overview of the pertinent imaging findings of the different forms of Osteosarcomas. 2. Familiarize the participant with the types of Osteosarcomas, imaging appearance before surgery, after surgery with/without residual/recurrent disease. 3. Show exemplary cases of typical and more rare Osteosarcomas found in our practice.

Educational Goals / Teaching Points
1. Review the types of Osteosarcomas and different variants/subtypes. 2. Discuss the imaging findings of typical and atypical (primary vs secondary) Osteosarcomas on Radiograph, CT, NM and MRI. 3. Demonstrate post surgical appearances after resection and recurrence 4. Review the differential diagnosis of Osteosarcomas.

Key Anatomic/Physiologic Issues and Imaging Findings/Techniques
Osteosarcomas are classified according to the histologic pattern as: 1. Primary Osteosacoma: 1.1. Intramedullary/central 1.1.2. Conventional osteosarcoma: most common. 1.1.3. Low-grade central osteosarcoma. 1.1.4. Telangiectatic osteosarcoma. 1.1.5. Small cell osteosarcoma. 1.2 Surface 1.2.1. Parosteal osteosarcoma. 1.2.2. Periosteal osteosarcoma. 1.2.3. High-grade surface osteosarcoma. 2. Secondary osteosarcoma. Plain Radiograph: Conventional plain radiograph is very useful for identification of osteoid matrix, sunburst appearance, Codman's triangle, and permeative pattern of bone destruction. Magnetic resonance imaging: Identifies the extension of the lesion in the medullary canal, extracompartmental extension into soft tissues, joints, skipped lesions and distant metastasis. Nuclear medicine: Tc99 bone scan is used for detection of metastasis. Positron Emission Tomography (PET): can help with the metastatic workup and/or evaluation of local recurrence. When planning to biopsy a potential sarcoma, surgeon should be consulted to plan the biopsy track that requires excision to reduce the chance of seeding.

Conclusion
Osteosarcoma is the most common type of cancer that arises in bones after malignant neoplasms of marrow origin, and it is usually found at the end of long bones, often around the knee. Usually affects young patients under the age of 20, and it is thought to occur more often in males than females. Different histological subtypes, histological grading and location of Osteosarcoma lead variable imaging appearance. However, there are some imaging features that can help differentiate between Osteosarcomas and other bone tumors. Adequate identification of the tumor with adequate biopsy planning will affect patient outcome and treatment.