[Malignant tumors of long bones in children: differential diagnosis and the role of imaging methods].

Purpose Of The Study: The aim of the study was to analyze primary malignant tumors and tumor-like lesions of long bones, in relation to their localization, characteristics and distribution in age groups, in children and young adults, and to assess the role of radiography and magnetic resonance imaging (MRI) in their diagnosis.

Material: Sixty-four patients, aged between 3 and 20 years, who were referred to us with the diagnosis of a suspected malignant long-bone tumor of osseous or cartilage origin in the period from 2000 to 2004 were included in the study.

Methods: Plain radiography and MRI were carried out on the same day. For MRI, the Magnetom Open Viva system (magnetic field strength of 0.2 T) was used and examination comprised a conventional STIR (corresponding to fat saturation) and a T-weighed sequence. Most patients also underwent post-contrast examination with paramagnetic contrast medium infusion.

Results: In 26 children (40.6 %) a primary malignant tumor of osseous or cartilage origin was diagnosed; one child (1.5 %) had a giant-cell tumor. The definitive diagnoses in 37 children (57.9 %) included osteomyelitis in 12, fatigue fracture in 11, posttraumatic myositis ossificans in three children, and miscellaneous diagnoses in the remaining 11 children (one, cartilaginous exostosis; three, unicameral bone cyst; two, non-ossifying fibroma; one, fibrous dysplasia; one, subperiosteal abscess; one, histiocytosis; one, foreign body; one, negative MRI findings).

Conclusions: To confirm the diagnosis of a malignant long-bone tumor, high quality X-ray and MRI are essential; CT examination is recommended in specific indications. The results of imaging methods cannot be assessed without reference to each other. Primary malignant tumors of long bones usually involve a large soft-tissue mass, and an exclusively intraosseous localization is rare. Osteosarcoma often invades the epiphysis. In making the differential diagnosis of primary malignant bone tumors, special attention must be paid to differentiation from osteomyelitis or fatigue fractures. The majority of juvenile bone lesions of any origin are usually detected between 10 and 13 years of age. These pathologic lesions are most frequently localized in the distal or proximal transition zones between the diaphysis and metaphysis.