Osteosarcoma: subtle, rare, and misleading plain film features.

Locally Aggressive Fibrous Dysplasia Mimicking Malignancy: A Report of Four Cases and Review of the Literature

“…Owing to considerable overlap in imaging features of locally aggressive fibrous dysplasia and fibrous dysplasia with malignant transformation, a biopsy is necessary for definitive diagnosis when atypical features are present. The most important pathologic differential diagnosis is the lowgrade, central (intramedullary) osteosarcoma which is strikingly similar to locally aggressive fibrous dysplasia [8,13,19]. Low-grade central osteosarcoma is a rare intramedullary well-differentiated tumor with clinical, imaging, and histologic features similar to those of fibrous dysplasia.…”

Imaging Osteosarcoma

“…However, early detection may cause diagnostic issues and tumors may be mistaken for benign lesions [13]. In these circumstances cross sectional imaging may indicate aggressive features suggestive of OS [14]. Rarely an expanding type of tumor may be, confined to the intramedullary cavity with no apparent aggressive features.…”

“…Rarely an expanding type of tumor may be, confined to the intramedullary cavity with no apparent aggressive features. Osteosclerotic OS confined to the intramedullary cavity have been confused with avascular necrosis [14,15]. An OS may resemble an osteoblastoma or osteoid osteoma as a lytic defect with calcification or ossification within the defect and surrounded by sclerosis [14,16].…”

“…Radiographs may indicate a fibrous cortical defect or a Brodie's abscess. A CT scan depicts the tumor in an intra-cortical location [14,17].…”

Bone tumour simulators

“…The many appearances of osteomyelitis may simulate almost the entire spectrum of bone tumours, and osteomyelitis should be considered the classic example of a bone tumour simulator (Rosenberg et al 1995, Malloy et al 1992, McGrath et al 1994, Kaweblum et al 1993, Mulligan, Kransdorf 1993. In its early phases, osteomyelitis may be abnormal on bone scan with no plain film findings.…”