Case Report Submitted by:Robbie Honey Date accepted: 30 August 2007 Radiological Category:Principal Modality (1): Principal Modality (2): Musculoskeletal CT/MRI General Radiography Faculty Reviewer: Sandra A. A. Oldham, MD

Case History 16 year-old African American male who presents with 3 weeks of pain and swelling in his left thigh. Pain is gradually getting worse (greatest amount 5/10) as well as the swelling. The pain is worse with activity and bending the leg. There is no history of trauma or fall. Parents have also noticed the patient has begun to limp. Patient has taken pain medication only once.

Radiological Presentations

Non-contrast CT

Radiological Presentations T1 Post Contrast T2

Conventional osteosarcoma Parosteal osteosarcoma High grade surface osteosarcoma Dedifferentiated parosteal osteosarcoma Osteochondroma Periosteal osteosarcoma Which one of the following is your choice for the appropriate diagnosis? After your selection, go to next page. Test Your Diagnosis

The conventional radiograph shows an extensive osseous tumor involving the diaphysis of the left femur with a “cumulus cloud” appearance. There is a marked sunburst type periosteal reaction that is prominent on the medial aspect of the femur. The tumor appears largely cortically based with extension into the surrounding soft tissues and likely medullary involvement. No pathological fractures. CT shows that the lesion is predominantly on the surface of the femur. In addition there is extension into the soft tissue with a large central component that is not mineralized. MRI shows similar findings to CT with areas of low signal on T1 corresponding to dense mineralization as well as a large soft tissue mass with an area of non- enhancement likely representing necrosis. In addition, within the medullary cavity there is diminished T1 signal intensity and increased T2 signal intensity representing either peritumoral edema or infiltrative extension of the tumor. Parosteal osteosarcoma High-grade surface osteosarcoma Periosteal osteosarcoma Dedifferentiated parosteal osteosarcoma Findings: Differentials: Findings and Differentials

Parosteal OS4>90 Dedifferentiated POS1<10 Periosteal OS1>80 High-grade surface OS1<10 % OS survival J & A Osteosarcoma Surface Variants Surface Variants

Parosteal osteosarcoma is the most common surface osteosarcoma, typically affecting patients in the second to fifth decades of life and women more commonly. They typically occur in the long tubular bones, with the femur being the predominant site. Parosteal osteosarcomas are particularly common on the posterior surface of the distal portion of the femur and typically arise in a metaphyseal location. The radiographic abnormalities are highly characteristic. A large, radiodense, oval, or spheroid mass possessing lobulated or irregular margins is evident. Typically, it is attached in a sessile fashion to the external cortex. A thin radiolucent line, or cleavage plane, may separate the remaining portion of the tumor from the underlying bone. Overall the tumors tend to have a “mushroom- like” configuration. Involvement of the medullary cavity is minimal. Grossly the tumors are rock-hard, ivory white, and well defined with a sharp interface between the tumor and overlying soft tissues. Histologically these are generally regarded as low-grade osteosarcoma. Treatment is complete surgical extirpation, with local recurrence of 100% if incomplete removal. Discussion

Dedifferentiated parosteal osteosarcoma represents a tumor in which there is association between conventional parosteal osteosarcoma and high-grade sarcoma (osteo, fibro, or malignant fibrous histiocytoma) and can occur either primarily or secondarily. Most common from 3 rd to 5 th decades and women greater then men. Most commonly the posterior distal femur is involved. Radiographically, appears very similar to conventional parosteal osteosarcoma. However frequently there are areas of lucency that may correspond to areas of high grade tumor within low grade tumor. In addition, arteriograms often show localized hypervascularity that tends to correspond to areas of high grade sarcoma. Discussion

Periosteal osteosarcoma is an infrequent neoplasm that predominates in the second and third decades of life. Involvement of the diaphysis of a long tubular bone, especially the femur or tibia, is typical. Periosteal osteosarcomas are variable in size and on radiographs appear as lesions on the bone surface. The tumor is limited to the cortex, which is thickened and irregular externally; this feature is commonly accompanied by nonhomogeneous, radiating osseous spicules that extend from the superficial region of the cortex into the adjacent soft tissues and are linear and perpedicular to the long axis of the parent bone. Attachment tends to be broad based. It should be emphasized that the medullary cavity, with rare exception, is uninvolved. Histologically, periosteal osteosarcoma is a form of relatively low to intermediate grade chondroblastic osteosarcoma arising from the bone surface. Discussion

High-grade surface osteosarcoma is the least common of all the forms of osteosarcoma. It occurs most often in the second and third decades. Men are more commonly affected (4:1). The femur is the most common location. There are no radiographic features that are specific to HGS. It may appear as a radiolucent mass with minimal intralesional calcification on the surface of the involved bone and thus mimic periosteal osteosarcoma. Alternatively, it may form a radiopaque “sunburst” lesion confined to the periosteal surface and overlying soft tissues. Grossly, HGS is not rock-hard, well defined, bosselated, and ivory white such as conventional perosteal osteosarcoma. Primary dedifferentiated OS also has these features. Additionally HGS does not have the appearance of well-formed, grayish blue hyaline cartilage such as periosteal OS. Histologically, the hallmark of HGS is the presence of pure, high-grade sarcoma. Discussion

The gold standard in imaging diagnosis of osteosarcoma remains the conventional radiograph. CT, MRI, and radionuclide examination are more useful for defining the extent of the neoplasm, including metastases, and its relationship to surrounding neurovascular structures. On MRI the neoplasm is typically of low signal intensity on T1-weighted spin echo, high intensity on T2 weighted images, and enhances with IV gadolinium. The distinction between dedifferentiated parosteal OS and high grade surface OS requires the use of histology and gross correlation. The distinction between high grade neoplasms (parosteal OS / HGS) and low grade neoplasms is important because of the indication for chemotherapy in high grade lesions. Discussion

Osteosarcoma, osteoblastic, high grade (High-grade surface osteosarcoma vs. dediffentiated parosteal osteosarcoma) Diagnosis

Miller, Mark D. Review of Orthopaedics. 4 th ed. Saunders, Raymond, Kevin A. Surface Osteosarcoma. In: Clinical Orthopaedics. Vol September, – 148. Resnick, Donald. Krandorf, Mark J. Tumor and Tumor-Like Lesions of Bone: Imaging and Pathology of Specific Lesions. In: Bone and Joint Imaging. 3 rd Edition. Elsevier Saunders, Wang, Lisa L. Chintagumpala, Murali. Gebhardt, Mark C. Osteosarcoma: Epidemiology, pathogenesis, clinical presentation, diagnosis, and histology. *Chart, pathology, and radiographic example slides adapted with the permission of A. Kevin Raymond, M.D., M.D. Anderson Cancer Center References