Osteochondromyxomas (OMX) are very rare benign tumors with both a chondroid and osteoid matrix mostly seen within the Carney complex.
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Epidemiology
Generally, osteochondromyxomas are extremely rare. Within the Carney complex, they occur in about 1% of the patients and are usually seen early in life often even before 2 years. In adults, they can appear as a separate entity 1,2.
Associations
Osteochondromyxomas are a rare criterion and are associated with other features of the Carney complex 1,2.
Diagnosis
The definitive diagnosis of osteochondromyxoma is based on a combination of typical clinical and pathological features. On imaging, osteochondromyxomas are rather unspecific 1.
Diagnostic criteria
Diagnostic criteria according to the WHO classification of soft tissue and bone tumors (5thedition) 1:
- variable amounts of cellular chondroid and osteoid matrix
- extensive myxoid changes
- other symptoms of the Carney complex
Clinical presentation
The typical complaint is a painless mass. It might be also found within a skeletal survey for the carney complex.
Pathology
Osteochondromyxomas are tumors with a chondroid and osteoid matrix and extensive myxoid changes 1.
Location
The tumor has been found in the following locations 1-4:
- facial bones and skull including the sellar region
- diaphyseal areas of long bones (tibia and radius)
- chest wall/ribs
- spine
Macroscopic appearance
Macroscopically osteochondromyxoma usually appears as a well-circumscribed, gelatinous, cartilaginous, light-yellowish, hemorrhagic tumor usually without a capsule that can show cortical erosion 1,2.
Microscopic appearance
Microscopic features of osteochondromyxomas include the following 1:
- variable cellularity in an abundant myxoid, cartilage-like and partly osteoid matrix
- chondroblast-like and osteoblast-like cells
- occasional mitoses
Immunophenotype
Immunohistochemistry stains might be occasionally positive for S100 1.
Genetics
Osteochondromyxoma is associated with inactivating mutations in the tumor suppressor gene PRKAR1A on chromosome 17q22-24 within the Carney complex 1-4.
Radiographic features
General imaging features of osteochondromyxoma are heterogeneous and vary with location 1,2. A ring-like or bubbly appearance has been described for radiographs and cross-sectional imaging 3:
- lytic or mixed sclerotic and lytic lesion
- expansile or permeative growth
Plain radiograph
On plain radiographs desmoplastic fibroma of bone will usually show the following characteristics 3,4:
- osteolytic or mixed osteolytic/mildly sclerotic matrix
- well-defined or partly well-defined margins
- possible endosteal scalloping
CT
CT might show a soft tissue density with calcifications and/or osteoid matrix and sometimes cortical erosions.
MRI
In addition to the general imaging features MRI displays the following 3-5:
Signal characteristics are usually as follows:
- T1: heterogeneous, mixed-signal intensity (isointense or hypointense to muscle)
- T2: heterogeneous, predominantly, high signal intensity
- T1 C+ (Gd): heterogeneous enhancement
Radiology report
The radiological report should include a description of the following:
- form and location
- tumor margins and transition zone
- cortical breakthrough
- endosteal scalloping
Treatment and prognosis
The tumor can be managed surgically and complete excision is curative, however, with incomplete resection, local recurrence is quite common 1.
History and etymology
The Carney complex was first described by J. Aidan Carney in 1985 2. However, the term ‘Carney bone tumor’ as a substitute for osteochondromyxoma is not recommended.
Differential diagnosis
Conditions that can mimic the presentation and/or the appearance of desmoplastic fibroma of bone include 1-4:
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