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chondromyxoid fibroma

Tuesday 3 February 2004

fibromyxoid chondroma of bone

Definition: Chondromyxoid fibroma (CMF) is a rare benign tumor of the appendicular skeleton of young adults.

Images

- CHONDROMYXOID FIBROMA. NB: spindle-stellate cells; myxohyaline stroma; coarse basophilic calcification

Chondromyxoid fibroma (CMF) is a benign tumor characterized by lobules of spindle shaped or stellate cells in an abondant myxoid to chondroid stroma. The lobules are separated by a more cellular stroma rich in spindle shaped to rounded cells and containing varying numbers of pleomorphic cells or multinucleated giant cells.

Almost half of the tumors involve the long bones, although the ilium and the small bones were also common sites.

Clinical Features

The chondromyxoid fibroma is slightly more common in men, usually in the second decade of life.

Patients range from 3 to 70 years of age; about 60 percent are between 10 and 30 years of age. A male predominance of approximately 2 to 1 has been reported in many sertes, whereas others have found an equal predilection.

The presenting symptom is usually pain; a mass is rare. The pain is often mild, transient, and of long duration (an average of 22 months in one series).

As many as 15 percent of cases are discovered as incidental radiographic findings, especially in the ribs and ilium.

Localization

Most tumors occur in the long bones with a predilection for the proximal portion of the tibia. Approximately 25 percent of cases occur in flat bones, mainly the ilium.

Other locations in descending order of frequency include the small tubular bones of the hands and feet, vertebrae, ribs, and femur.

Radiology

Roentgenograms show a sharply marginated, lobulated, lucent defect in the metaphysis. The tumor involved the medullary bone in an eccentric fashion, and the cortex was thinned and expanded. Periosteal reaction and soft tissue extension were uncommon. Mineralization was identified in 13% of the lesions.

Chondromyxoid fibroma of long bones is typically an eccentrically located, metaphyseal lesion that may extend into the epiphysis.

Most are sharply demarcated, purely lytic defects with scalloped margins.

Intralesional calcified matrix is rare.

Chondromyxoid fibromas involving the tubular bones of the hands and feet tend to be centrally located and expand the bone symmettically.

Tumors in the flat bones are loculated and have an irregular contour.

Vertebral lesions often have a more aggressive appearance with frequent extension through the periosteum.

A subperiosteal chondromyxoid fibroma has been reported.

Macroscopy

The tumor typically ap¬pears sharply circumscribed, often lobulated, firm, gray-white, or blue-gray.

If the cortex has been eroded, an intact periosteum is stil’ evident overlying the tumor.

Rare soft tissue implants are grossly identical to their intraosseous counterparts.

Microscopy

- pseudolobular architecture
- spindle shaped or stellate cells
- abondant myxoid stroma to chondroid stroma

It is a benign tumor characterized by lobules of spindle shaped or stellate cells in an abondant myxoid to chondroid stroma. The lobules are separated by a more cellular stroma rich in spinelle shaped to rounded catis and contain¬ing varyingnumbers of pleomorphic cells or mul¬tinucleated giant cells.

Histologically, the tumors were almost always arranged in lobules, which were prominent (macrolobular) or somewhat indistinct (microlobular).

The tumor cells are spindle-shaped or stellate and arranged in a myxoid matrix.

Calcification was seen in more than one third of the cases but was rarely prominent.

Hyaline cartilage and chondroblastoma-like areas were not uncommon.

Approximately 18% of tumors showed bizarre nuclei.

Permeation of bony trabeculae is uncommon.

The margin of a completely resected chondromyxoid fibroma is microscopically sharply demarcated, either by bone or connective tissue if the tumor has eroded through the bone.

The term chondromyxoid fibroma reflects the variety of tissues that characterize this lesion.

The most helpful diagnostic feature is the nodular architecture of myxoid lobules.

The fibrous component usually accounts for only a small portion of the tumor and consists mainly of narrow fibrous septa separating the lobules. These septa contain large venules, muscular arteries, multinucleated giant tells, and, occasionally, osteoid.

When a chondromyxoid fibroma is curetted, it tends te fracture through the fibrous septa, making the latter inconspicuous in curetted material.

The fibrous septa may be seen only as a focal rim around isolated fragments, or as a short segment within a myxoid nodule.

The myxoid areas have a highly variable cellularity and a broad range of cytologie appearances. The variation can occur within a single nodule, as well as between nodules.

Cells range from closely packed fibroblasts with narrow, small nuclei to large tells with nuclear aberrations. The most distinctive tells have eosinophilic cytoplasm and one or more long cytoplasmic processes.

Nuclei can be homogeneously hyperchromatic, have clumped chromatin, or be vacuolated. Binucleated and trinucleated tumor tells are frequent.

Cells occasionally occur in small lacunae, but well-formed hyaline cartilage matrix is usually sparse or absent.

About one third of tumors have markedly atypical tells with large, often bizarre nuclei, resem¬bling the cens of a high-grade chondrosarcoma.

Mitotic figures are usually absent, however, and only about 10 percent of tumors have foci of necrosis.

The periphery of the lobules is typically hypercellular, and the cells in this area often resemble chondroblasts.

Immunochemistry

Many of the cells in chondromyxoid fibroma are S-100 positive, in keeping with their cartilaginous nature.

Ultrastructure

Ultrastructurally, the stellate tells have irregular tell processes, scalloping of the tell membrane, and often have abundant cytoplasmic fibrils.

Variants

- Juxtacortical chondromyxoid fibroma (CMF)

  • It can be a poorly recognized subtype which arises on the surface of long bones and erodes the cortical surface causing a periosteal reaction.
  • This entity should be included in the differential diagnosis of bone surface lesions as it may be mistaken for a more aggressive neoplasm.
  • CMF should be included in the differential diagnosis of bone surface lesions. The clinical and radiologic findings must be known.
  • The morphology of this lesion is similar to conventional CMF with the exception of focal exuberant calcification.
  • Conservative therapy is the treatment of choice.

Differential diagnosis

- myxoid lesions of bone

  • chondrosarcoma (myxoid chondrosarcoma)
  • chordoma
  • myxoma of bone
  • fibromyxoma of bone

Chondromyxoid fibroma can and should be distinguished from chondrosarcoma and chordoma, two tumors which have the potential to metastasize.

Chondrosarcoma is the lesion most often confused with chondromyxoid fibroma. Both tumors have a nodular growth pattern with prominent peripheral cellu-larity, atypical cells, and myxoid stroma. Reactive osteoid or bone can be seen along the edges of the tumor nodules in both lesions.

Some microscopic fields in chondromyxoid fibroma are indistinguishable from chondrosarcoma, however, although the periphery of chondromyxoid fibroma nodules may be quite cellular, the central portions are oftenless cellular than even low-grade chondrosarcome. Large areas of chondroid matrix tend to favor chondrosarcoma, but their absence is of no differential value.

Radiographic findings are of the greatest importance in distinguishing these microscopically overlapping lesions. Chondromyxoid fibroma has a sharply defined margin with a sclerotic tint, whereas chondrosarcoma does not. Chondrosarcomas usually have at least some "fluffy" calcification of the matrix, a feature lacking in chondromyxoid fibroma.

Cytogenetics

- 6q anomalies (11793371, 10746672)

  • recurrent 6q25 anomalies (10746672)
  • pericentromeric inversion inv(6)(p25q13) (9831204)

- ins(5;2)(q13;p21p25) and 2p deletion (8453600)
- t(3;6) (9648559)

Treatment and management

Treatment is conservative surgical removal; approximately one fourth of the patients have recurrence.

The prognosis is excellent for most cases, even when there is a recurrence. En bloc resection is the treatment of choice.

Prognosis

Curettage with bone grafting results in a recurrence rate of about 10 to 15 percent, most seen within 2 years, but some seen up to 9 years later.

Patients under the age of 15 years are especially prone to recurrence.

Rahimi et al. noted that the tumors in young patients tended to be more myxoid and had greater nuclear atypia than those in older individuals.

Others have found no correlation between recurrence and histology findings.

Soft tissue implantation is rare, and one implanted tumor had an intra-arterial component.

One untreated recurrent lesion progressed radiographically and then ceased to grow.

Rare lesions, however, have acted in an unusually aggressive manner with soft tissue spread requiring amputation. One lesion arising in the sacrum spread into soft tissue and dura resulting in death.

No well-documented case of chondromyxoid fi¬broma has metastasized. However, a malignant transformation to chondrosarcoma in the absence of radiation therapy has developed.

Another patient with a chondromyxoid fibroma developed a postradiation fibrosarcoma.

See also

- cartilaginous lesions of bone
- myxoid lesions of bone

Textbook reference

- Tumors of the bones and joints. AFIP, 1992. Pages 95-100. ISBN: 1881041085

References

- Immunohistochemical analysis for Sox9 reveals the cartilaginous character of chondroblastoma and chondromyxoid fibroma of the bone. Konishi E, Nakashima Y, Iwasa Y, Nakao R, Yanagisawa A. Hum Pathol. 2010 Feb;41(2):208-13.PMID: 19801163

- Juvenile juxtacortical chondromyxoid fibroma of bone: a case report. Jhala D, Coventry S, Rao P, Yen F, Siegal GP. Hum Pathol. 2008 Jun;39(6):960-5. PMID: 18400252

- Juxtacortical chondromyxoid fibroma of bone: a unique variant: a case study of 20 patients. Baker AC, Rezeanu L, O’Laughlin S, Unni K, Klein MJ, Siegal GP. Am J Surg Pathol. 2007 Nov;31(11):1662-8. PMID: 18059222

- Recurrent anomalies of 6q25 in chondromyxoid fibroma. Safar A, Nelson M, Neff JR, Maale GE, Bayani J, Squire J, Bridge JA. Hum Pathol. 2000 Mar;31(3):306-11. PMID: 10746672

- Wu CT, Inwards CY, O’Laughlin S, Rock MG, Beabout JW, Unni KK. Chondromyxoid fibroma of bone: a clinicopathologic review of 278 cases. Hum Pathol. 1998 May;29(5):438-46. PMID: 9596266

- Chondromyxoid fibroma of bone: a clinicopathologic review of 278 cases. Wu CT, Inwards CY, O’Laughlin S, Rock MG, Beabout JW, Unni KK. Hum Pathol. 1998 May;29(5):438-46. PMID: 9596266

- Chondromyxoid fibroma of the skull base: a tumor which may be confused with chordoma and chondrosarcoma. A report of three cases and review of the literature. Keel SB, Bhan AK, Liebsch NJ, Rosenberg AE. Am J Surg Pathol. 1997 May;21(5):577-82. PMID: 9158683

- Chondromyxoid fibroma of bone: thirty-six cases with clinicopathologic correlation. Zillmer DA, Dorfman HD. Hum Pathol. 1989 Oct;20(10):952-64. PMID: 2793160