Chondromyxoid fibroma

Chondromyxoid fibroma is a type of cartilaginous tumor.^[1]

Most cases are characterised by GRM1 gene fusion or promoter swapping.^[2] It can be associated with a translocation at t(1;5)(p13;p13).^[3]

A chondromyxoid fibroma (CMF) is an extremely rare benign cartilaginous neoplasm which accounts for < 1% bone tumours.

Epidemiology

The majority of cases occur in the second and third decades, with approximately 75% of cases occurring before the age of 30 years 1,12-15. There is no recognised gender predilection. Examples have however been seen in patients up to the age of 75 years. In some series there is a male predilection 12 whilst in others no such distribution is found 2

Clinical presentation

Typically patients present with progressive pain, often long standing and/or bony swelling and restricted range of movement in affected limb 3,12. The latter is most often the case in bones with little overlying soft tissues (e.g. short tubular bones of the hands and feet).

Most chondromyxoid fibromas are located in the metaphyseal region of long bones (60%), and may extend to the epiphyseal line and even rarely abut the articular surface 3,12. They are almost never just epiphyseal 3. The classical site is the upper 1/3rd of tibia ( which accounts for 25% of all cases) with the small tubular bones of the foot, the distal femur and pelvis being other relatively common locations 12.

Rarely occur in the skull or skull base.^[4]

Pathology

The tumor comprises a variable combination on chondroid, myxoid, and fibrous tissue components organized in a pseudolobulated architecture 20.

On gross examination they are typically seen as solid glistening tan-gray intraosseous masses.

Occasional osteoclast-like giant multinucleated cells are encountered particularly at the periphery. Most cells are morphologically bland, and mitotic figures are rare or absent 13.

Radiographic features

Plain film often seen as a lobulated, eccentric radiolucent lesion long axis parallel to long axis of long bone no periosteal reaction (unless a complicating fracture present) geographic bone destruction: almost 100% well defined sclerotic margin: 86% there can be presence of septations (pseudotrabeculation): 57% 2 there can be presence of matrix calcification in a small proportion of cases: 12.5%1 MRI MR features are often not particularly specific. Signal characteristics include

T1 - low signal T1 C+ (Gd) - the majority (~70%) tend to show peripheral nodular enhancement ~ 30% diffuse contrast enhancement and this can be either homogeneous or heterogeneous 19 T2 - high signal Bone scan A scintigraphic "doughnut sign" has been described in this tumour type 11. However, this is very non-specific and can be found in a plethora of other bone lesions.

Treatment and prognosis

They are benign lesions and malignant degeneration is rare. They are usually treated with curettage which however have a high recurrence rate of 25%. As such if an en-bloc resection is possible this is advisable

References