Chondromyxoid fibroma

Chondromyxoid fibroma is a rare benign bone tumor accounting for approximately 1% of all benign bone tumors. Chondromyxoid fibroma affects all age groups. It is more commonly seen during the second and third decades of life. Men are more commonly affected than women. Chondromyxoid fibroma arising from the physeal remnant is the commonly proposed theory in the pathogenesis of this tumor. It is predominantly found in the metaphyses of the long bones. The bones involved include tibia, distal femur, pelvis, feet and hands. Chromosome 6 appears to be involved in chondromyxoid fibroma. Over expression of the glutamate receptor gene GRM1 in patients with chondromyxoid fibroma via promoter swapping and gene fusion has been observed. The hallmark of chondromyxoid fibroma is pain, swelling, and pathological fracture. The mainstay of treatment for chondromyxoid fibroma is surgery (curettage and bone grafting).

In 1948, Jaffe and Lichtenstein described chondromyxoid fibroma for the first time.^[1]

Chondromyxoid fibroma can be classified based on imaging findings.

• The Enneking surgical staging system (also known as the MSTS system) for benign musculoskeletal tumors is based on radiographic characteristics of the tumor host margin.^[2]
• It is widely accepted and routinely used classification.

• The exact etiology of chondromyxoid fibroma is unknown.^[3]
• Chondromyxoid fibroma arising from the physeal remnant is the commonly proposed theory in the pathogenesis of chondromyxoid fibroma.^[4]
• It is predominantly found in the metaphyses of the long bones.^[5]
• The bones involved by chondromyxoid fibroma includes tibia, distal femur, pelvis, feet and hands.^[6]

• Chromosome 6 appears to be involved in chondromyxoid fibroma.^[5][7]
• The non-random clonal abnormalities involves 6p25, 6q13 and 6q23.^[5]
• Whole-genome mate-pair sequencing and RNA sequencing showed over expression of the glutamate receptor gene GRM1 in patients with chondromyxoid fibroma via promoter swapping and gene fusion.^[8]

There are no established causes of chondromyxoid fibroma.^[9]

Chondromyxoid fibroma must be differentiated from the following bone disorders:^[10]

• Chondromyxoid fibroma is a rare benign bone tumor accounting for approximately 1% of all benign bone tumors.^[11]
• Chondromyxoid fibroma affects all age groups.
• It is more commonly seen during the second and third decades of life.
• Men are more commonly affected than women.
• There is no racial predilection to chondromyxoid fibroma.

There are no established risk factors for chondromyxoid fibroma.

There is insufficient evidence to recommend routine screening for chondromyxoid fibroma.

Common complications of chondromyxoid fibroma include:

• Pathological fracture
• Premature epiphyseal closure
• Limb-length discrepancy
• Angular deformity

Prognosis is generally good for chondromyxoid fibroma.

• Prognostic variables include:
  • Children
  • When the Tumor is more lobulated with abundant myxoid material

• Biopsy is the diagnostic study of choice for chondromyxoid fibroma.
• Biopsy findings under low and high power fields are given below:^[12][13]

• It has a biphasic appearance
• It has lobules and pseudolobules of fibromyxoid tissue with hypercellular area.
• The cells are spindle-shaped or stellate-shaped and contain hyperchromatic nuclei.
• Multinucleated giant cells and fibrovascular tissue may be present between the lobules.
• Hypocellular area with chondroid material is seen.

• The tumor shows myxoid stroma mixed with stellate cells.
• In addition, an area of pleiomorphic cells with bizarre nuclei may be seen.

• The majority of patients with chondromyxoid fibroma have a positive history of:
  • Pain
  • Swelling
  • Stiffness
  • Pathological fracture

Common physical examination findings of chondromyxoid fibroma include:

• Deformity

• Swelling
• Decreased range of motion
• Warmth over the affected area

There are no diagnostic laboratory findings associated with chondromyxoid fibroma.

There are no ECG findings associated with chondromyxoid fibroma.

X-ray findings include:^[14][15]

• The tumor appears as a lytic, eccentric metaphyseal lesion.

• Size of the lesion may vary from 2 to 10 cm.
• It has a sharply demarcated border from the adjacent bone.

• It may show scalloped and sclerotic rim
• Calcification is usually not seen
• The tumor may show cortical expansion.

There are no echocardiography/ultrasound findings associated with chondromyxoid fibroma.

• CT scan confirms the x-ray findings.^[16]
• It is superior to x-ray for analyzing the expansion of the lesion and cortical breach.

MRI findings of chondromyxoid fibroma include:^[17][18]

• T1 image: Chondroid and myxoid tissues produce low signals.
• T2 image: Chondroid and myxoid tissues produce high signals.

• Increased uptake is seen in chondromyxoid fibroma.

There are no other diagnostic studies associated with chondromyxoid fibroma.

There is no treatment for chondromyxoid fibroma; the mainstay of therapy is surgery.

Surgery is the mainstay of treatment for chondromyxoid fibroma.^[19][20]

Types

1. Intralesional Curettage

• It is the mainstay of treatment for chondromyxoid fibroma.^[20]
• The defect is filled with bone graft or bone cement in form of polymethlymethacrylate(PMMA).

2. En Bloc Excision

• It usually reserved for recurrent cases.^[21]

Recurrence Rate

• The recurrence rate is about 25% for chondromyxoid fibroma.^[22]

There are no established measures for the primary prevention of chondromyxoid fibroma.

There are no established measures for the secondary prevention of chondromyxoid fibroma.

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