Chondromyxoid Fibroma

Chondromyxoid fibromas are rare benign bone tumors composed of variable prportions of fibromyxoid tissue and cartilage tissue. They predominantly occur in adolescents and young adults and are usually found in the metaphyses of the long tubular bones, especially the tibia and femur near the knee joint. They may cross open growth plates into epiphyses or epiphyseal equivalents (e.g., the tibial tubercle, as in our case).

Chondromyxoid fibromas have a geographic pattern of bone destruction and are typically located eccentrically in the bone. Internally, the lesion is usually lucent, but ridges or septa can sometimes be seen. Calcifications, if present, can be seen on CT but not radiographs.

Peripherally, these tumors have a scalloped, sclerotic margin. The lesion can erode or balloon from the cortex, resulting in a buttress periosteal reaction.

Differential considerations on radiography include aneurysmal bone cyst, non-ossifying fibroma (cortical ballooning or destruction is rare), fibrous dysplasia (centrally located), adamantinoma (much more aggressive, older patients), and osteofibrous dysplasia (more sclerotic, younger patients).

MRI findings are nonspecific: intermediate to low signal intensity on T1-weighted images and high signal intensity on T2-weighted images.

Lateral and frontal radiographs of the proximal tibia of a 13-year-old boy show a lucent, expansile, metaphyseal lesion without a perceptable sclerotic border and with a narrow zone of transition. Axial CT image shows extension of the tumor through the anterior proximal tibial cortex with a large soft tissue component Pathologic analysis confirmed a diagnosis of chondromyxoid fibroma. Axial images show a T1-hypointense and T2-hyperintense soft tissue mass with extensive T2-hyperintensity in the surrounding marrow. Fat-saturated post-contrast sagittal image shows heterogeneous, predominantly peripheral, enhancement.

Also of interest: cartilage lesions by age and location.

References

• Greenspan A, Jundt G, Remagen W. Cartilage (Chondrogenic) Lesions. In Differential Diagnosis of Orthopaedic Oncology, 2nd Edition. 2007 Lippincott Williams & Wilkins; pp 207-212.
• Mehta S, Szklaruk J, Faria SC, Raymond AK, Whitman GJ. Radiologic-pathologic conferences of the University of Texas M. D. Anderson Cancer Center: Chondromyxoid fibroma of the sacrum and left iliac bone. AJR Am J Roentgenol. 2006 Feb;186(2):467-9.
• Wilson AJ, Kyriakos M, Ackerman LV. Chondromyxoid fibroma: radiographic appearance in 38 cases and in a review of the literature. Radiology. 1991 May;179(2):513-8.