Imaging features of low-grade central osteosarcoma of the long bones and pelvis

Abstract

LGCOS has a variable appearance on radiographs. A frequent pattern is a slow-growing large intracompartmental fibro-osseous lesion with varying amounts of septal ossification associated with focal areas of aggression. A homogeneously sclerotic pattern was also noted. Imaging with CT or MRI was helpful in every instance in our series in identifying areas of soft tissue extension or cortical disruption suggestive of a low-grade malignancy.

MDM2 and CDK4 immunohistochemistry is a valuable tool in the differential diagnosis of low-grade osteosarcomas and other primary fibro-osseous lesions of the bone

“…12 The infiltrative tumoral pattern, cortical disruption and soft-tissue extension cannot totally provide a differential diagnosis, but are more suggestive of the low-grade malignancy of a lowgrade central osteosarcoma. 12,25 The presence of a cloud-like tumor matrix pattern on radiological findings, reflecting the presence of intra-tumoral bone formation, is also a good argument for lowgrade central osteosarcoma. Another pitfall when diagnosing low-grade central osteosarcoma is the liposclerosing myxofibrous tumor, a lesion possibly linked to fibrous dysplasia and characteristically MDM2 and CDK4 in fibro-osseous lesions of the bone located in the proximal femur, at the base of the femoral neck.…”

Central low-grade osteosarcoma: a diagnostic challenge

“…On cross-sectional imaging cortical breach and soft-tissue extension is usual. Overt aggressive features including cortical destruction, soft tissue extension and periosteal reaction may be lacking [7].…”

“…Although fibrous dysplasia may fill the medullary cavity and compress the cortex with marked thinning and even loss of the cortex in small and slender bones, particularly the ribs and the fibula, progressive invasion does not occur. Histologically, permeation of the cortex and Haversian system is not expected, and entrapment of the host bone trabeculae at the perimeter of the lesion is not seen [3,7,8].…”

“…Diagnosis on imaging may be challenging; however, some worrying features are usually found and one large study has documented that the lesions are often interpreted as "benign appearing overall with focally aggressive features" [7]. Lesions are most commonly lytic with varying thick and coarse trabeculation or thin incomplete trabecula.…”

“…While low-grade fibrous dysplasia-like osteosarcoma may have imaging features in part mimicking fibrous dysplasia, more ominous features are usually identifiable in which cortical disruption and soft-tissue extension is expected in most instances [7]. Similarly, in a setting where thick coalescent plates of tumour are present, prompting consideration of Paget's disease, appropriate radiological correlation should allow differentiation [9].…”