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Radiology > MUSCULOSKELETAL
Enchondroma and Enchondromatosis
Article Last Updated: Dec 12, 2006
AUTHOR AND EDITOR INFORMATION
Section 1 of 12  
Author: Felix S Chew, MD, MBA, EdM, Professor, Department of Radiology, Vice Chairman for Radiology Informatics, Section Head of Musculoskeletal Radiology, University of Washington
Felix S Chew is a member of the following medical societies: American Roentgen Ray Society, Association of University Radiologists, and Radiological Society of North America
Coauthor(s):
Catherine Maldjian, MD, Associate Professor, Director, Radiology Research Center, Department of Radiology, Westchester Medical Center
Editors: Michael A Bruno, MD, Associate Professor, Departments of Radiology and Medicine, Pennsylvania State University College of Medicine; Director, Radiology Quality Management Services, Milton S Hershey Medical Center, Pennsylvania State University College of Medicine; Bernard D Coombs, MB, ChB, PhD, Consulting Staff, Department of Specialist Rehabilitation Services, Hutt Valley District Health Board, New Zealand; Murali Sundaram, MBBS, FRCR, FACR, Consulting Staff, Department of Diagnostic Radiology, The Cleveland Clinic Foundation; Robert M Krasny, MD, Consulting Staff, Department of Radiology, The Angeles Clinic and Research Institute; Felix S Chew, MD, MBA, EdM, Professor, Department of Radiology, Vice Chairman for Radiology Informatics, Section Head of Musculoskeletal Radiology, University of Washington
Author and Editor Disclosure
Synonyms and related keywords:
chondroma, chondrosarcoma, Ollier's disease, Ollier disease, Maffucci syndrome, dystrophic calcifications, benign cartilaginous neoplasms, benign bone neoplasms, osseous neoplasms, pathologic bone fracture, hyaline cartilage rests
Background
Enchondromas are benign cartilaginous neoplasms that are usually solitary lesions in intramedullary bone. The primary significant factors of enchondromas are related to their complications, most notably pathologic fracture, and a small incidence of malignant transformation, which may be associated with pathologic fracture.
When multiple enchondromas coexist, the diagnosis of enchondromatosis should be considered.
Multiple enchondromas may occur in 3 distinct disorders:
- Ollier disease is a nonhereditary disorder characterized by multiple enchondromas with a predilection for unilateral distribution. The enchondromas can grow large and can be disfiguring.
- Maffucci syndrome is nonhereditary and is less common than Ollier disease. This syndrome results in multiple hemangiomas in addition to enchondromas.
- Metachondromatosis consists of multiple enchondromas and osteochondromas. Of the 3 disorders, metachondromatosis is the only one that is hereditary, which is by autosomal dominant transmission.
Pathophysiology
Enchondromas are ectopic hyaline cartilage rests in intramedullary bone. The lesions replace normal bone with mineralized or unmineralized hyaline cartilage, thereby generating a lytic pattern on radiographs or, more commonly, a lytic area containing rings and arcs of chondroid calcifications. The lesions likely arise from cartilaginous rests that are displaced from the growth plate.
Endosteal growth may occur and does not imply malignant transformation in the hands and feet, wherein the lesions appear to be more cellular. Although the extent of cellularity is not correlated with malignant transformation, mitotic figures are seldom seen in the lesions, and their presence may be correlated with malignancy. Pathologic fracture predisposed by thinning of the cortex is not typically associated with malignancy in the hands and feet; however, in other areas such as the long bones and flat bones, pathologic fracture is suggestive of malignant transformation.
Complete transgression through the cortex with a soft-tissue component is highly suggestive of malignancy. Although malignant transformation to several types of tumors is reported, chondrosarcoma is the most common by far.
Frequency
United States
Enchondromas account for 12-14% of benign bone neoplasms and 3-10% of osseous neoplasms in general (Unni, 1996).
Mortality/Morbidity
Most often, enchondromas are of no consequence and patients are asymptomatic. Enchondromas are not life threatening; however, painful malignant transformation should be the primary concern and cannot be excluded, even in the presence of a benign appearance on radiographs and images from other modalities. Malignant transformation is virtually nonexistent in the hands and feet but may be seen in the long bones and flat bones.
- In a patient with enchondromatosis, the incidence of chondrosarcoma is much higher than in other patients, and the rate may be as high as 50% (Unni).
- In Maffucci syndrome, hemangiomas also may undergo sarcomatous transformation; however, osseous lesions do so more frequently and most commonly result in chondrosarcomas.
- In the event of malignant transformation to chondrosarcoma, patients with low-grade chondrosarcoma have a 5-year survival rate of 65-85%, whereas patients with the highest-grade chondrosarcomas have a 5-year survival rate of 15% (Springfield et al, 1996).
Race
No racial predilection is known.
Sex
Enchondromas occur equally in males and females.
Age
Solitary enchondromas most often are discovered in those aged 20-40 years. Ollier disease is usually detected in those aged 0-10 years.
Anatomy
Solitary enchondromas are intramedullary lesions, although they may expand enough to cause endosteal scalloping of the cortex. They have a predilection for the small bones of the hands and feet, where most occur. Of these, half are in the proximal phalanx, followed in frequency by the metacarpal and middle phalanx and, lastly, by the distal phalanges and carpus. Other locations are the shoulder, pelvis, and long bones. Enchondromas tend to occupy the diaphyseal region in the short tubular bones and the metaphyseal region in the longer bones. Ollier disease occurs with highest frequency in the long bones.
Approximately 50% of solitary enchondromas are found in the hands, typically in the middle and distal portions of the metacarpals and the proximal portions of the phalanges (Unni). The next most common sites are the proximal and distal parts of the femur and the proximal part of the humerus. Enchondromas at the mid shaft of the tibia are rare.
Clinical Details
When patients have pain and/or rapid growth of the lesion, malignant transformation should be suspected, even in the absence of suggestive radiographic findings. Enchondromas are metabolically active and may continue to grow and evolve throughout the patient's lifetime; thus, progressive calcification over a period of years is not unusual. Loss of calcification in a focal region suggests malignant degeneration with destruction of the underlying enchondroma by sarcomatous tissue.
Primary clinical complications include pathologic fracture and malignant transformation, which may be concomitant. In particular, pathologic fracture does not imply malignant transformation in the hands and feet, in which endosteal scalloping and cortical thinning may be extensive without malignant transformation.
When the lesion has calcifications, the primary differential diagnoses are bone infarct and chondrosarcoma. When the lesion is purely lytic, as shown on radiographs, the differential diagnosis consists of benign lytic lesions such as nonossifying fibroma, simple bone cyst, fibrous dysplasia, eosinophilic granuloma, and clear cell chondrosarcoma (which tends to involve the end of the bone—in particular, the proximal humerus).
Preferred Examination
Initially, radiography is the imaging modality of choice. If further characterization is necessary, magnetic resonance imaging (MRI) or computed tomography (CT) scanning is performed. If uncertainty remains, bone scanning may be helpful, but some lesions require biopsy.
Limitations of Techniques
X-ray findings may not demonstrate or adequately characterize subtle calcifications to the extent that CT scans do. When calcifications are not present on either examination, MRI may be performed, which should reveal the classic appearance of noncalcified hyaline cartilage. Dystrophic calcifications in bone infarcts may be difficult to differentiate from chondroid matrix with ionizing radiation, and MRI may be helpful in these cases. Occasionally, dystrophic calcifications in bone infarcts may be difficult to differentiate from enchondromas on plain radiographs. When a clearly serpiginous rind of sclerosis encapsulates the lesion, the diagnosis of bone infarct is straightforward; however, when this finding is not present, MRI may be useful in differentiating the 2 entities. In lesions in which calcifications are not seen radiographically, the diagnosis may be made with the help of MRIs. CT scans may demonstrate the presence of calcification not depicted on radiographs. Chondrosarcoma—in particular, low-grade chondrosarcoma—may be indistinguishable from enchondroma. Certain imaging features may be helpful in distinguishing enchondroma from chondrosarcoma (see Radiograph section below). However, even a lesion with no imaging features suggestive of malignancy and an imaging appearance compatible with an enchondroma should be resected when it is associated with pain. Low-grade chondrosarcoma may be indistinguishable from enchondroma on all images, and the diagnosis may be difficult, even with histologic evaluation.
Chondrosarcoma
Other Problems to be Considered
Bone infarct
Benign lytic lesions - Nonossifying fibroma, simple bone cyst, fibrous dysplasia, eosinophilic granuloma, clear cell chondrosarcoma
Findings
A classic pattern of calcifications, described as rings and arcs, is pathognomonic when it is seen in the hands. In the long bones, calcifications may be difficult to distinguish from the dystrophic calcifications seen in bone infarction. In addition, radiographs may not depict the rings and arcs of calcifications, particularly in the hands and feet.
Low-grade chondrosarcoma may be indistinguishable from enchondroma; however, in most cases, chondrosarcoma has certain imaging features that are indicative of its aggressive behavior. Cortical breakthrough, soft-tissue mass, and deep endosteal scalloping of the cortex are 3 features that are described more frequently in chondrosarcoma. However, deep endosteal scalloping with consequent pathologic fracture in the small bones of the hands and feet does not imply malignancy, because enchondromas are more cellular and expansile in these locations.
In Ollier disease, enchondromas often appear to be larger than they do in other conditions. Because enchondromas occur in young patients and can be large, growth of the affected limbs may be adversely affected, and pathologic fractures may occur. Enchondromatosis can occasionally have the appearance of linear lucencies, in which the chondrocytes appear to line up in a vertical orientation along the length of the bone.
In Maffucci syndrome, associated soft-tissue hemangiomas are seen. Soft-tissue hemangiomas typically have numerous rounded calcifications with central lucencies, which are consistent with phleboliths on plain radiograph. T2-weighted MRIs of these lesions show high-signal-intensity tubular structures, which are consistent with slow flow in vascular channels.
Metachondromatosis has associated osteochondromas, which differ from conventional osteochondromas in that they point toward rather than away from the joint.
Degree of Confidence
On radiographs, the degree of confidence in the diagnosis of an enchondroma depends on the clinical situation and the appearance of the lesion. In the presence of pain, almost regardless of appearance, further investigation is warranted. Lesions that are predominantly lucent or are nonuniformly mineralized often require further investigation as well.
False Positives/Negatives
In most cases, enchondroma and a low-grade chondrosarcoma cannot be reliably distinguished on the basis of radiographic findings alone. A calcified enchondroma can also mimic the appearance of a calcified marrow infarct.
Findings
The features of enchondroma on CT scan are the same as those depicted on radiographs.
Enchondromas are endosteal lesions with a lobular morphology and variable mineralization. Often, the mineralization is in the form of rings and arcs, which correspond to calcification around lobules of cartilage. A pathologic fracture may be present. Sometimes, endosteal scalloping is present, but this feature may be suggestive of degeneration of the enchondroma to a chondrosarcoma. Enchondromas should not penetrate the cortex or extend into the soft tissues.
If a densely mineralized or uniformly mineralized lesion has a region that is lucent, degeneration of the enchondroma to a chondrosarcoma is suggested, and biopsy is likely necessary.
Degree of Confidence
As with radiographs, the degree of confidence in the diagnosis of an enchondroma with CT scanning depends on the clinical situation and the appearance of the lesion. The absence of pain, uniform or dense mineralization, and endosteal scalloping or cortical penetration are all indications of an enchondroma. However, if the patient lacks any of these features, further investigation may be necessary.
False Positives/Negatives
Distinguishing an enchondroma from a low-grade chondrosarcoma is often problematic; sometimes, the diagnosis cannot be resolved without a biopsy. Because cartilage lesions are often not uniform at histologic examination, the entire lesion may need to be removed at biopsy.
Findings
MRI findings may be useful in distinguishing enchondromas in the long bones from bone infarcts. Typically, bone infarcts are encapsulated by a serpiginous rind of decreased signal intensity on T1- and T2-weighted images. Frequently, this rind is subtended by a high-signal-intensity line. This finding has been called the double-line sign, and it consists of a high-signal-intensity rind circumscribed by and immediately adjacent to a low-signal-intensity rind on T2-weighted images.
Conversely, enchondromas tend to have lobulated borders with a cluster of numerous tiny locules of high-signal-intensity foci on T2-weighted images that appear to coalesce with one another and reflect the high fluid content of hyaline cartilage. On T1-weighted images, enchondromas demonstrate low-to-intermediate signal intensity.
When a calcific chondroid matrix is observed on radiographs, decreased signal intensity is expected to occur in those areas on images obtained with all MRI pulse sequences. These areas may become particularly pronounced on gradient-echo images.
Degree of Confidence
When combined with a typical appearance on radiographs and an absence of pain, the diagnosis of enchondroma with MRI findings can be made with a high degree of confidence. Enchondromas may also be incidental findings at routine examination, such as MRI of the knee. If the lesions have a typical appearance, a confident diagnosis may be made; however, the acquisition of correlative radiographic findings is often prudent.
False Positives/Negatives
Occasionally, enchondromas can be difficult to distinguish from other intraosseous benign and malignant lesions on the basis of MRI findings alone. Correlation with other results, particularly radiographic results, may help. The presence of bone pain always warrants further investigation.
Findings
Ultrasonography is not used in the diagnosis of enchondroma.
Findings
With technetium-99m (99mTc) radionuclide bone scanning, findings are typically negative in uncomplicated enchondromas, but the presence of pathologic fracture results in intense activity at the fracture site. In patients with multiple enchondromas or patients in whom an enchondroma is actively calcifying, radionuclide bone scans may show increased activity, but the activity is typically less intense than that of intramedullary chondrosarcomas.
Positron emission tomography (PET) using 18-fluorodeoxyglucose (18-FDG) has been applied increasingly to the evaluation of tumors. Using PET to evaluate enchondromas—particularly to distinguish benign enchondromas from low-grade chondrosarcomas—has been reported in small series. In a study by Feldman et al (2005), 11 enchondromas were studied by PET with 18-FDG; the maximum standard uptake values (SUVs) ranged from 0.8 to 1.8. The authors established a maximum SUV of 2.0 as the cutoff between benign and malignant; 10 of the 11 chondrosarcomas in their study had maximum SUVs ranging from 2.4 to 12.4. Feldman et al recommended 18-FDG PET as an adjunct for the evaluation of aggressive cartilage lesions. A hypometabolic lesion would not require biopsy.
Degree of Confidence
Radionuclide bone scanning is one method used to assess lesions depicted on radiographs or MRIs that are presumed to be enchondromas. If the bone scan results are negative, the possibility of a malignancy (eg, chondrosarcoma) is extremely remote. If the scan results are positive, biopsy is typically necessary. Radionuclide bone scan findings are not reliable in differentiating enchondroma from calcified marrow infarct.
False Positives/Negatives
Radionuclide bone scan findings are nonspecific; therefore, one cannot reliably diagnose a focal bone lesion on the basis of these findings alone. However, the physiologic information provided by a bone scan, when combined with information from other imaging modalities, can be helpful.
The 18-FDG PET imaging study of cartilage lesions by Feldman et al included one lesion that was considered a borderline chondrosarcoma. This lesion had a maximum SUV of 1.4, which was below the value of 2.0 that they used as the cutoff between benign and malignant.
Findings
Angiography is not used in the diagnosis or evaluation of solitary enchondroma. In Maffucci syndrome, angiography may play a secondary role in identifying the extent and origin of the vascular malformation.
CT-guided percutaneous needle biopsy occasionally is indicated in the management of enchondroma. However, because benign and low-grade malignant cartilage lesions may be difficult to distinguish at histologic examination, the risk of sampling error usually precludes a confident diagnosis. Therefore, needle biopsy is not generally useful.
If CT scans show a densely mineralized or uniformly mineralized lesion with a lucent region, degeneration of the enchondroma to a chondrosarcoma is suggested, and biopsy is likely necessary.
| Media file 1:
Frontal radiograph of the right hand demonstrates a lytic expansile lesion in the fifth metacarpal bone, with thinning of the cortex that has a somewhat scalloped appearance. A pathologic fracture is noted, but no appreciable calcifications are seen in the lesion. |
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Media type: X-RAY
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| Media file 2:
Detail of a lytic expansile lesion in the fifth metacarpal bone in the right hand (same patient as in Image 1). There is thinning of the cortex with a somewhat scalloped appearance. A pathologic fracture is noted, but no appreciable calcifications are seen in the lesion. |
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Media type: X-RAY
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| Media file 3:
Frontal radiograph of the left hand demonstrates an expansile lytic lesion in the proximal phalanx of the fifth digit with a distinct zone of transition, thinning of the cortex, and a pathologic fracture. The lesion involves the diaphysis and approaches the end of the bone near the metacarpophalangeal joint. This finding is not uncommon in enchondromas of the small bones. Note the fuzzy calcifications in the matrix of the lesion. |
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Media type: X-RAY
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| Media file 4:
Detail of an expansile lytic lesion in the proximal phalanx of the fifth digit with a distinct zone of transition, thinning of the cortex, and a pathologic fracture (same patient as in Image 3). |
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Media type: X-RAY
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| Media file 5:
Radiograph of the right femur demonstrates a calcified intramedullary lesion in the distal shaft (same patient as in Images 6-7). |
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Media type: X-RAY
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| Media file 6:
Radiograph of the right femur demonstrates a calcified intramedullary lesion in the distal shaft (same patient as in Images 5 and 7). |
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Media type: X-RAY
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| Media file 7:
Axial computed tomography image demonstrates a fluffy calcific matrix within the medullary canal of the distal femur (same patient as in Images 5-6). The surrounding cortex is intact. |
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Media type: CT
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| Media file 8:
Frontal radiograph of the right thigh demonstrates coarse calcifications in the distal femur (same patient as in Images 9-12). |
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| Media file 9:
Axial T1-weighted magnetic resonance imaging study shows an intramedullary lesion with low signal intensity and lobular morphology in the distal femur (same patient as in Images 8 and 10-12). The endosteal aspect of the cortex is not affected. |
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Media type: MRI
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| Media file 10:
Coronal T1-weighted magnetic resonance imaging study demonstrates predominantly decreased signal intensity within a lesion in the distal femur (same patient as in Images 8-9 and 11-12). The lesion has a lobular morphology. No endosteal scalloping is noted. |
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Media type: MRI
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| Media file 11:
Axial T2-weighted magnetic resonance imaging study shows regions of high signal intensity in the lesion (same patient as in Images 8-10 and 12). No surrounding edema is noted. |
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Media type: MRI
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| Media file 12:
Coronal T2-weighted magnetic resonance imaging study demonstrates small lobulated foci of increased signal intensity separated by a background mesh of decreased signal intensity (same patient as in Images 8-11). The adjacent cortex is intact. |
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Enchondroma and Enchondromatosis excerpt Article Last Updated: Dec 12, 2006
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