Chondromyxoid Fibroma Workup

Updated: Sep 24, 2018
  • Author: Michael S Clarke, MD; Chief Editor: Omohodion (Odion) Binitie, MD  more...
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Workup

Imaging Studies

Radiography

On radiographs, [23, 24]  chondromyxoid fibromas (CMFs) are well-defined, eccentric, elongated, radiolucent lesions. Like many bone tumors, CMFs occur most frequently in the metaphysis of the proximal tibia and the distal femur. Epiphyseal occurance has not been reported. Other reported locations are the pelvis and the first metacarpal.

A common appearance is a bubbly, expansile, eccentric, elongated, metaphyseal, lytic lesion. A rare diagnostic feature is a eccentric, nearly hemispherical "bite" from the cortical margin without periosteal reaction (see the image below). The greatest dimension of a CMF is less than 10 cm. The margins are usually sclerotic with scalloped borders and may demonstrate mild cortical expansion. The lesions can extend into the diaphysis but do not cross the physeal plate.

Radiograph showing the "bite" out of the metaphyse Radiograph showing the "bite" out of the metaphyseal cortex that is a diagnostic feature of chondromyxoid fibroma.

Trabeculations within the tumor, which reflect bony ridges formed around a lobulated tumor may be visible on radiographs. Matrix calcifications are unusual. [25]

When CMF involves the vertebrae (quite rare) radiographs may show a more aggressive appearance. [26] CMFs of the small bones of the hands or feet (rare) are more central and expansile. CMFs may have associated or secondary aneurysmal bone cysts (ABCs).

Computed tomography

On computed tomography (CT), mild cortical expansion may be observed, and the lesions have a density greater than fluid throughout. CT scans also exhibit characteristic lack of mineralization within CMFs. CT may be superior to conventional radiography for analysing the expansion of the lesion, cortical breakthrough, and internal mineralization. [27]

Magnetic resonance imaging

Chondroid and myxoid tissues, as well as any normal hyaline cartilage within the lesion, have an intermediate-to-high signal on proton-density and T2-weighted magnetic resonance imaging (MRI) and a low signal on T1-weighted images (see the image below). [28, 29, 27] Fibrous tissue components have a variable appearance, depending on their vascularity. Because of their diverse tissue components, CMFs have a heterogeneous appearance. They are typically solid but can have cystic areas. Secondary ABCs have typical septations and fluid-fluid levels.

Magnetic resonance imaging (MRI) scan of chondromy Magnetic resonance imaging (MRI) scan of chondromyxoid fibroma (T1 image).

Bone scanning

CMFs usually have increased activity on bone scintigraphy.

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Biopsy

Biopsy is used for histologic examination. [30] A generous tissue sample is required for an accurate diagnosis, because small biopsies may not be representative.

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Histologic Findings

Microscopically, CMFs are lobulated or pseudolobulated, with peripheral condensation of more cellular tissue within the lobules. Composed of myxoid or chondroid tissue, the center of each lobule is hypocellular. The surrounding stroma is denser, with spindle-shaped cells, blood vessels, and occasional multinucleate giant cells.

Tumor nuclei may be hyperchromatic, are of moderate size, and may lie in chondroid lacunae. Nuclear atypia can be observed, but mitoses are rare or absent. Microcalcification is present in 15-20% of cases, with an increased incidence in older patients. (See the image below.)

Close-up of a lobule of a chondromyxoid fibroma. Close-up of a lobule of a chondromyxoid fibroma.

Scattered areas of hyalinization, xanthomatous changes, cholesterol clefts, and cystic degeneration may be noted, including secondary ABCs. The tumors have a heterogeneous immunohistochemical staining pattern, with the central chondroid areas staining positively for S-100 protein and the peripheral, hypercellular tissue staining diffusely for muscle and smooth muscle actin. [31, 32] None of the cells express desmin.

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Staging

Local staging typically includes plain radiography and MRI or CT. Because CMF does not metastasize, there is no need for routine chest radiographs or other systemic staging studies. A total skeletal bone scan is generally advisable during the initial evaluation to assess local activity and to confirm the solitary nature of the tumor.

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