An 11-year-old boy presented to the emergency department with a 10-day history of pain in his right thigh following an accidental fall. The pain was described as a dull ache and rated 3/10. He was seen and sent home without having any x-rays. He managed to mobilize with difficulty using crutches. As the lower leg pain worsened, his mother contacted the GP. Subsequently, she was advised to bring him back and that is when an x-ray was taken. He denied any paraesthesia or pain elsewhere. He had did not have any significant past medical or surgical history.
X-ray: There is a fracture of the right distal femur with some medial displacement through a multiseptated lucent lesion. The lesion has a narrow zone of transition along its inferior margin and a slightly ill-defined zone of transition along the superior margin. The lesion is mildly expansile along the medial aspect of the distal femur.
CT scan: pathological fracture through the distal shaft of the femur secondary to the presence of a well-demarcated lobulated lucent lesion in the medulla. There is endosteal scalloping on the anterior aspect of the femur. The tumour has a narrow zone of transition. It measures approximately 3 x 2 x 6 cm. Ill-defined fluffy soft tissue calcification is seen in the soft tissues adjacent to the fracture- not seen on the x-ray- is likely to represent periosteal reaction. Joint effusion is present.
MRI scan: Multiloculated non-expansile lesion is seen in the right distal femur metadiaphysis. This lesion is eccentric, extending to the medial cortex with endosteal scalloping. Nor obvious extraosseous extension is identified. This lesion demonstrates a narrow zone of transition. There is a pathological displaced fracture within this lesion with posterior and proximal displacement of the distal fragment. There is periosteal reaction noted in the femur, however, this would be secondary to the pathological fracture.
Background
Chondromyxoid fibroma is one of the rarest benign tumours of cartilaginous origin. It accounts for less than 0.5% of bone tumours and less than two per cent of benign bone tumours. It mainly affects the metaphysis of long bones, the proximal tibia being the most common location. It is frequently diagnosed in the second decade of life and is slightly more common in males[1]
Clinical Perspective
Typically presents as long-standing pain with mild swelling around the affected area. It can lead to pathological fractures
Imaging Perspective
On plain radiographs as osteolytic expansile lobulated lesions without periosteal reaction, associated with well-defined borders and sclerotic rim.
On CT scan the appearance varies but typically shows cortical thinning and/ or destruction of the cortex. Internal mineralisation appears in less than 10% of cases. On MRI the lesions tend to be homogenous isointense to muscle tissue on TW1 and mostly heterogeneous of intermediate intensity on T2 STIR[2]
Outcome
Multiple modalities of treatment are available; however, some patients require a combination of therapies.
1) Surgery - which includes intralesional curettage +/- bone grafting +/- cementation.
2) Intraoperative adjuvants - including cryotherapy, phenol or cauterisation.
Prognosis is generally good and the majority of cases recover with no complications.
However, complications have been reported with:
1) Post-surgical complications including wound infections and fractures at the site of curettage.
2) Recurrence: recurrence rate correlates with the age of diagnosis. The younger the patient the more likely to have recurrences
3) Malignant transformation is rare, with figures reported between 1-2%[3]
Take-Home Message / Teaching Points
Chondromyxoid Fibroma is one of the rare benign bone lesions, but it’s a diagnosis to keep in mind when faced with a typical radiological picture especially in patients in the second decades of life.
Chondromyxoid Fibroma
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Based on the provided X-ray, CT, and MRI images, the right distal femur (distal thigh) shows a lesion with a tendency toward a lytic, expansile change. The lesion has a relatively well-defined boundary, with thinned but generally intact cortical bone in some areas, and a sclerotic rim in certain regions. The X-ray shows no significant or only mild periosteal reaction. CT reveals a lesion with relatively low density and no obvious calcification or clear internal bone structure, with local cortical destruction or thinning. On MRI, the T1 signal is similar to muscular tissue, and on T2/STIR sequences, it mostly appears as a mixed intermediate to high signal with a well-defined margin. The lesion is located primarily in the diaphysis and metaphysis, with no apparent invasion of surrounding soft tissue or large-scale swelling or effusion.
Considering the patient’s age (11 years), clinical presentation (persistent dull pain after a fall, moderate intensity), and the imaging characteristics described above, the following diagnoses and differential diagnoses are primarily considered:
Combining clinical factors (onset during adolescence, persistent dull thigh pain, lack of significant systemic symptoms) and imaging findings (well-defined, expansile lytic lesion with a sclerotic rim, thinning of the cortex, and minimal soft tissue involvement), the most likely diagnosis is:
Chondromyxoid Fibroma.
A biopsy is recommended for further confirmation. Histopathological findings and biopsy results are crucial for definitive tumor characterization.
For Chondromyxoid Fibroma and other benign bone tumors, the most common treatment approaches include:
Whether after surgery or during conservative management, a gradual rehabilitation program is essential. This helps avoid reinjury or stress-related fractures at the lesion site. Below is an example of a FITT-VP (Frequency, Intensity, Time, Type, Volume & Progression) approach:
Throughout the rehabilitation process, close attention should be paid to any pain, swelling, or limitation of function in the affected limb. If significant discomfort arises, consult the physician or rehabilitation therapist promptly to adjust the exercise plan.
This report is based on the current imaging and clinical information provided and is for reference only. It does not replace an in-person consultation or professional medical advice. Actual treatment and rehabilitation plans should be formulated and carried out by a multidisciplinary team including orthopedics, radiology, and rehabilitation specialists, tailored to the patient’s specific condition.
Chondromyxoid Fibroma
