[Abstract] Objective To investigate the imaging characteristics and differential diagnosis of endogenous chondrosarcoma of long bones. Data and methods To analyze the data of 11 cases of endogenous chondrosarcoma of long bones confirmed by surgery or puncture pathology, and to summarize their X-ray plain film, CT and MRI manifestations. Results Among the 11 cases, 3 occurred in the upper femur, 3 in the lower femur, 2 in the upper tibia, 1 in the upper fibula, and 1 in the lower tibia, and the other case was a bilateral symmetrical lesion in the lower femur and upper tibia. All cases showed cystic bone destruction on X-ray, and 10 cases showed patchy, striated, ring-like calcification or ossification; 5 cases showed bone destruction and different degrees of calcification on CT examination, 2 cases showed bone cortical fracture and soft tissue masses around them; 2 cases showed medium signal on T1WI and high signal on T2WI on MRI examination; no periosteal reaction was seen on imaging in all cases. Conclusion The imaging manifestation of endogenous chondrosarcoma in long bones has certain characteristics, and the correct diagnosis can be made by combining X-ray plain film, CT and MRI, and CT and MRI have greater value for differential diagnosis. Lei Zhidan, Department of Radiology, Henan Provincial People’s Hospital
[Keywords] Long bone; endogenous chondrosarcoma; tomography; X-ray computer
Chondrosarcoma is a relatively common tumor, occupying the third place among benign bone tumors, mainly occurring in short bones, but also in long bones and pelvis [1. 2], while those occurring in the bone marrow cavity are called endogenous chondrosarcoma. Endogenous chondrosarcomas occurring in short bones are more frequently reported, but those occurring in long bones are less frequently reported. The authors analyzed the imaging data of 11 cases of endogenous chondrosarcoma of long bones confirmed by surgical pathology or puncture biopsy to improve the understanding of this disease.
1 Data and methods
There were 11 cases in this group, 7 males and 4 females, with ages ranging from 5 to 53 years and a median age of 28 years. The duration of the disease ranged from 3 months to 20 years, with an average of 5 years. The clinical manifestations were mainly pain and discomfort at the involved area, one case had skeletal deformation of the knee joint, and six cases could palpate a hard mass. All cases were confirmed by surgery or puncture pathology.
All cases had X-ray frontal and lateral plain radiographs, and 5 cases had CT plain scans, 2 of which had CT enhanced scans. 2 cases had MRI examinations.
2 Results
2.1 Site of lesion 10 of the 11 cases in this group had a single lesion, and 1 case had a bilateral symmetrical multiple lesion.
2.2 X-ray features Among the 11 cases in this group, 4 cases were completely located in the bone marrow cavity, with lobulated or round-like translucent areas and sclerotic margins, with no change in the bone cortex; 1 case showed lateral growth of the destruction area and thinning of the bone cortex; 6 cases (including 1 case with multiple lesions) showed distending changes, with foveal bone septa and distending thinning of the bone cortex in all cases, and 2 of them showed localized bone cortex defects. Ten cases in this group had significant calcification, with patchy and striated changes. one case had a combined pathological fracture. No periosteal reaction was observed in all cases.
2.3 CT and MRI manifestations Two cases showed that the lesion was completely located in the bone marrow cavity with oval hypodensity, one of them showed speckled calcification and the other one showed annular calcification; three cases showed that the lesion had distended changes with foveal septum and partial interruption of bone cortex with uneven density and speckled calcification. In two of the five CT cases, soft tissue masses were seen around the lesions, and the masses showed heterogeneous enhancement. 2 cases showed cystic destruction of bone in the lesion area on MRI, with heterogeneous medium signal on T1-weighted images and heterogeneous high signal on T2-weighted images; no soft tissue masses were seen in two cases.
3 Discussion
3.1 Overview Chondrosarcoma is a benign tumor, which is more common and occupies the third place among all benign bone tumors [2], accounting for 12% of benign bone tumors and about 3% of all bone tumors, and its incidence is relatively lower than that of osteochondrosarcoma. The incidence rate is relatively lower than that of osteochondroma. The short bones of the limbs are the most common, accounting for 58%, while the long bones of the limbs, pelvis, vertebrae and other parts of the body can occur. Those occurring in the cortex or subperiosteum are called exogenous chondromas; those occurring in the bone marrow cavity are called endogenous chondromas; those with multiple chondromas combined with malformations are called Ollier’s disease, and those with multiple chondromas combined with limb soft tissue hemangiomas are called Maffucci’s disease. All cases in this group were endogenous chondrosarcomas located in the bone marrow cavity. Endogenous chondrosarcoma can be seen at all ages, with onset from early childhood, and is most common from 20 to 40 years of age, with a peak at 30 years of age. Many endogenous chondrosarcomas are discovered accidentally during imaging for other reasons, as they have no conscious symptoms and often do not manifest until adulthood. The lesion may be solitary or multiple, and multiple lesions often have deformities. The main physical examination may reveal a local nodular mass with a hard texture and localized pressure pain. Joint movement is generally unimpeded, sometimes causing joint deformity. Endogenous chondrosarcoma is a tumor composed of lobulated hyaline cartilage with a fibrous envelope, mostly lobulated, and often with varying degrees of calcification near the blood vessels in the lobular space and in the stroma of the hypertrophic cartilage layer. Due to the reason of sampling, it is difficult to diagnose benign chondrosarcoma with or without sarcomatous changes in pathology.
3.2 Imaging features Endogenous chondrosarcomas occurring in long bones are more common in the lower femur and upper tibiofibula, and the lesions are relatively extensive, but their center is usually located in the epiphysis of the tubular bone [3]. x-ray plain radiographs show a central cystic distended hyaline area or map-like bone destruction, and the margins mainly show osteosclerosis, but there are also indistinct margins. The mass is often lobulated, and the bone around the lesion may often show arcuate compression or distension and deformation. The lesion may also invade the bone marrow cavity without compressing the adjacent bone cortex, and for most lesions X-rays can reveal calcifications of varying degrees, accounting for more than 50%, in different forms of punctate, striated, patchy, and annular forms, with annular calcifications being characteristic. Most believe that cystic bone destruction, marginal sclerosis and calcification within the destruction area are the typical signs for the diagnosis of this disease. If calcification is not found on X-ray plain film, it is difficult to diagnose, and there was one case in our group that was correctly diagnosed for this reason. CT has the obvious advantage of showing endogenous chondrosarcoma of long bones, which can clearly show the lesion in the medullary cavity in the form of lobulated, round-like bone destruction or swelling bone destruction, and swelling bone destruction can observe the thinning of bone cortex and whether the bone cortex is continuous. This suggests that the lesion has malignantly changed into chondrosarcoma. CT is sensitive to calcification within the lesion, which is of special value in the diagnosis of this disease, and calcification within the cystic translucency is considered to be the main basis for the diagnosis of endogenous chondrosarcoma [3]. On T2WI endogenous chondroma shows a lobulated high signal, which reflects a high ratio of water content to mucopolysaccharide component within hyaline cartilage, and on T1WI, endogenous chondroma shows a lobulated intramedullary lesion with a signal similar to that of skeletal muscle, and occasionally, a high signal is seen on T1WI, which may be due to bone marrow fat within the lesion, and the lesion T2WI signal on FSE is somewhat The T2WI signal of the lesion is reduced on FSE than on SE. The MRI of two cases in our group showed lobulated high signal on T2WI and lobulated intramedullary lesions on T1WI, with signals similar to those of skeletal muscle, similar to Cohen’s study. In our case, multiple lesions and skeletal deformities were diagnosed as Ollier’s disease, which showed signs of epiphyseal enlargement, thick and short diaphysis, and knee deformity in addition to the above-mentioned radiographic changes.
3.3 Differential diagnosis Although most endogenous chondromas of long bones have typical imaging features, atypical endogenous chondromas of long bones need to be differentiated from the following: (1) Mucinous fibroma of cartilage: usually located in the long tubular bones of the lower extremities, the typical presentation is a lesion with a long axis parallel to the backbone, eccentric oval bone destruction with rough beam-like intervals and little calcification. (2) Bone cysts: Mostly in the epiphysis of long tubular bones, with round or oval bony translucent areas with no structure inside, usually without calcification, often combined with pathological fractures. (3) Bone infarcts: foci occurring in the epiphysis with clear borders and runner-like margins. The affected bone is not distended and has relatively poorly defined borders, whereas endophytic chondromas of long bones often have sclerotic margins. Most MRI examinations can differentiate between the two, with bone infarcts having high-signal fat on T1WI and lacking high-signal cartilage on T2WI. A history of alcoholism, hormone abuse, pancreatitis, and deep sea diving occupations are more likely to be associated with bone infarcts. (4) Chondroblastoma: Like endogenous chondroblastoma of long bones, calcification is seen within it and a sclerotic ring is seen around it. However, the former tumors are mostly located in the epiphysis before epiphyseal healing, and those occurring under the articular surface may break through the end of the bone into the joint, while those located solely in the epiphysis without involving the epiphyseal plate are rare. In the latter case, the lesions are mostly located in the epiphysis and progress towards the diaphysis.
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