eMedicine - Chondromyxoid Fibroma : Article by Gregory Stacy, MD


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Chondromyxoid Fibroma

Last Updated: January 3, 2003

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Synonyms and related keywords: CMF, fibromyxoid chondroma, myxofibrous chondroma, primary osseous neoplasm, benign bone tumor, osseous tumor, lower extremity tumor

AUTHOR INFORMATION Section 1 of 12

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Author: Gregory Stacy, MD, Assistant Professor, Department of Clinical Radiology, University of Chicago Hospitals
Coauthor(s): John George, Karol Marcinkowski University of Medical Sciences

Gregory Stacy, MD, is a member of the following medical societies: American College of Radiology, American Roentgen Ray Society, and Radiological Society of North America

Editor(s): Michael A Bruno, MD, Chair, Department of Radiology, Maricopa Medical Center; Bernard D Coombs, MBChB, PhD, Assistant Professor, Department of Radiology, University of Colorado Health Sciences Center; Murali Sundaram, MBBS, FRCR, Department of Radiology, Mayo Clinic of Rochester; Robert M Krasny, MD, Visiting Assistant Professor of Radiology, University of California at Los Angeles Medical Center; Consulting Staff, Tower Imaging, Los Angeles, California; and Felix S Chew, MD, EdM, Vice-Chair for Education, Section Head of Musculoskeletal Radiology, Professor, Department of Radiology, Wake Forest University School of Medicine

INTRODUCTION Section 2 of 12

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Background: Chondromyxoid fibroma (CMF) is a rare benign tumor of the bone that was described by Jaffe and Lichenstein in 1948. CMF is most often found in the long tubular bones, especially the tibia and femur near the knee joint. CMF occurs predominantly in younger patients in the second or third decade of life.

Pathophysiology: The etiology of development of CMF is unknown. The tumor arises from the cartilage-forming connective tissue of the marrow space. Histologically, as its name implies, this benign cartilaginous neoplasm consists of chondroid, myxoid, and fibrous tissue in variable amounts, and microscopic evaluation of a wide area of the tumor may be necessary to identify all of the tissue subtypes. Osteoclastlike giant cells also may be present, as may small cysts and hemorrhagic zones. Focal calcification is found microscopically in approximately one fourth of patients, although any gross evidence of calcification is rare.

Frequency:

In the US: CMFs are among the rarest of the bone tumors, representing less than 1% of primary osseous neoplasms (approximately 2% of benign bone tumors).

Internationally: No data suggest that the international frequency of CMF is different than the frequency in the United States.

Mortality/Morbidity: CMF may present with a pathologic fracture through the tumor, which may lead to morbidity. If managed appropriately, the lesion is not fatal. If undiagnosed, the tumor continues to grow, occasionally infiltrating the surrounding soft tissues and causing further damage. Although CMF is considered to be a benign lesion, rare instances of malignant (featuring more prominent histologic atypia) and metastatic (eg, with spread to the lung) varieties have been reported. Malignant degeneration following radiation therapy in patients with CMF also has been reported; therefore, irradiation is contraindicated as a mode of therapy.

Race: No racial predilection has been observed.

Sex: Several reports claim a predilection in males, with a male-to-female ratio of 1.5-2:1. Other authors deny a sex predilection.

Age: The tumor is found predominantly in patients in the second and third decades of life; more than 80% of cases occur in patients younger than 36 years (although patients as young as 3 years and as old as 79 years have been reported). A second incidence peak may occur in patients aged 50-70 years.

Anatomy: Most CMFs (75%) occur in the bones of the lower extremity, particularly around the knee joint. CMF is localized to the femur (see Image 3) and tibia (see Image 13) in 50% of patients. The most common site is the proximal tibia, which accounts for approximately 30% of cases. The humerus, radius, and ulna also are affected, although reported percentages vary widely from study to study because of the rarity of the lesion. In addition, the small bones of the foot are relatively common sites, and lesions of the hands, skull, spine, and pelvis (see Image 25) have been reported.

Within the bone, the tumor typically originates in the metaphysis close to the physis. The tumor may extend into the epiphysis, the diaphysis, or both. Apophyses also may be affected (eg, the greater trochanter of the femur). In the long bones, the tumor is usually eccentric and ovoid in shape (see Image 14), with the long axis paralleling the length of the bone. In smaller bones, the tumor may occupy the entire volume of bone.

Clinical Details: Pain and local soft-tissue swelling are the most common presenting complaints (approximately 85% and 65% of patients, respectively). However, the duration of pain and swelling is quite variable; duration of pain averages approximately 22 months and duration of swelling averages approximately 10 months. This relatively long duration of symptoms denotes a slow tumor growth rate. Pathologic fracture is observed in some patients with painful tumors. Asymptomatic tumors may occasionally be detected incidentally on radiographs.

Preferred Examination: Conventional radiography provides the most useful diagnostic information of any imaging modality; however, definitive diagnosis can only be made using analysis of biopsy specimens. Unless contraindicated, MRI is recommended over CT for delineation of tumor extent prior to surgery (see Image 9).

Limitations of Techniques: Although findings on conventional radiographs may suggest the diagnosis of CMF, definitive diagnosis requires an analysis of biopsy specimens.

DIFFERENTIALS Section 3 of 12

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Aneurysmal Bone Cyst
Chondroblastoma
Chondrosarcoma
Enchondroma and Enchondromatosis
Eosinophilic Granuloma, Skeletal
Fibrous Cortical Defect and Nonossifying Fibroma
Fibrous Dysplasia
Giant Cell Tumor
Osteoblastoma

Other Problems to be Considered:

Desmoplastic fibroma

X-RAY Section 4 of 12

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Findings: On conventional radiographs, a CMF usually appears as a well-marginated, expansile, eccentric, lucent medullary lesion in the metaphysis of a long bone, ranging in length from 3-10 cm (see Image 1). The tumor may extend into the diaphysis (see Image 2) or, uncommonly, into the epiphysis (see Image 6). CMF may rarely be purely diaphyseal (see Image 10), but it is never solely epiphyseal. Essentially, the tumor may replace the bulk of a smaller bone. Smaller CMFs may appear to arise from the cortex of bone, and juxtacortical (exophytic) tumors have been reported.

Smaller tumors are usually round with a thin sclerotic margin (see Image 5) and uncommonly contain visible calcification or trabeculation. In larger lesions, remnants of cortical bone reinforcing the tumor at the periphery can appear on radiographs as trabeculation (see Image 23). These osseous ridges along the periphery are also responsible for the bubbly cystic radiographic appearance of CMF (see Image 22). A sclerotic scalloped border is typical. Compared with other cartilaginous tumors, the matrix of CMF uncommonly appears calcified on conventional radiographs (see Image 18).

Degree of Confidence: An eccentric, medullary, bubbly-appearing, metaphyseal lesion with scalloped sclerotic borders should prompt the radiologist to consider CMF in the differential diagnosis, particularly if the lesion is found in the proximal tibia. However, diagnosing CMF with a high degree of confidence by using imaging studies may be difficult because of the rarity of the tumor. An analysis of a biopsy specimen is always necessary for a definitive diagnosis.

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Related Articles

Aneurysmal Bone Cyst

Chondroblastoma

Chondrosarcoma

Enchondroma and Enchondromatosis

Eosinophilic Granuloma, Skeletal

Fibrous Cortical Defect and Nonossifying Fibroma

Fibrous Dysplasia

Giant Cell Tumor

Osteoblastoma

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CAT SCAN

Section 5 of 12

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Findings: After conventional radiography, CT scans may be used to further study the nature and extent of the suspected CMF (see Images 11-12). CT is the best imaging modality for detecting sclerotic margins and ridges (see Image 24) and matrix mineralization (see Image 19), and CT findings can depict the cortical integrity of the lesion. CT scans may show calcification within the tumor that is not visible on conventional radiographs.

Degree of Confidence: CT findings may reveal calcifications within the lesion that are not apparent on conventional radiographs; therefore, CT findings may increase the suspicion that a lesion is cartilaginous. Otherwise, CT scans add little to the diagnosis.

MRI Section 6 of 12

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Findings: MRI may be used in the management of CMF to observe the true extent of the lesion so that complete resection may be planned and potential recurrence may be avoided.

MRI findings of CMF are nonspecific. The tumor typically demonstrates low signal intensity on T1-weighted images (see Image 7, Image 16) and heterogeneous high signal intensity on T2-weighted images (see Image 26). Smaller lesions, as well as some larger lesions, may demonstrate homogeneously bright signal on T2-weighted images, often with a hypointense rim (see Image 17). Enhancement following intravenous administration of gadolinium is typically heterogeneous (see Image 8), often most prominent along the vascular borders of the tumor. Heterogeneity is believed to be the result of varying amounts of chondroid, myxoid, and fibrous tissues in the tumor, as well as any underlying cystic and/or hemorrhagic components.

Degree of Confidence: MRI findings of CMF are nonspecific and typically do not alter the degree of confidence in the diagnosis. The primary role of MRI is in preoperative planning (ie, evaluation of the extent of the tumor).

ULTRASOUND Section 7 of 12

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Findings: Ultrasound currently has no role in the diagnosis of CMF.

NUCLEAR MEDICINE Section 8 of 12

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Findings: Although increased radionuclide activity is demonstrated in CMFs on bone scans (see Image 21), nuclear medicine procedures are of limited use in the diagnosis or management of these lesions. The typically eccentric location of a CMF may be evident if the lesion is relatively small (see Image 15). Smaller lesions may be subtle if located adjacent to a growing physis or joint that typically accumulates radiotracer (eg, sacroiliac joint) (see Image 27). Increased flow may be apparent on the angiographic portion of a 3-phase study (see Image 20). Bone scintigraphy may be used to exclude the possibility of multiple lesions, which are highly uncharacteristic of CMF (see Image 4).

Degree of Confidence: Nuclear medicine studies add little to the degree of confidence in the diagnosis, although multiple lesions on a bone scan is highly uncharacteristic of a CMF.

ANGIOGRAPHY Section 9 of 12

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Findings: Angiography is of limited use in the diagnosis of CMF. Angiographic appearances are nonspecific, with the tumor demonstrating either minimal neovascularity or no internal vascularity, with or without surrounding vascular tissue. Angiography may be used to define surrounding vasculature or for planning embolization (uncommon).

Degree of Confidence: Angiography typically does not alter the degree of confidence in the diagnosis, but it may be used as a preoperative study.

INTERVENTION Section 10 of 12

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Intervention: Treatment in patients with CMF usually involves curettage or en bloc resection, with a preference for en bloc resection. Radiation therapy is contraindicated because of the risk of inducing malignancy. Periodic follow-up studies are indicated because of the significant recurrence rate of CMFs.

Medical/Legal Pitfalls:

Patients with CMF present with generic symptoms that are very similar to those of other benign and malignant bone tumors.

Imaging findings may be suggestive of CMF, but ultimately, an analysis of biopsy specimens is required for a definitive diagnosis.

The lesion shares some imaging features with chondrosarcoma, which is treated much more aggressively.

Special Concerns:

The recurrence of CMF after curettage has been documented in numerous patients, especially in younger patients. During studies, a definite correlation has been observed between a younger age in patients and the likelihood of recurrence.

Recurrent tumors retain the histologic and gross characteristics of the original tumor, and most recurrent tumors are observed in patients younger than 20 years.

PICTURES

Section 11 of 12

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