A 37-years-old male patient, with no known medical illness, complained of nine months of low back pain radiating in the right leg, initiated after weightlifting.
A pelvic radiograph (Fig.1) was initially performed, which demonstrated an asymmetry in the sacroiliac joints, with on the right reduced joint space and unsharply defined cortex of the joint and sacral foramina. Magnetic resonance imaging (MRI) showed a lobulated soft tissue mass located anterior to the right sacroiliac joint, arising from the cortex of the iliac bone. The mass is a homogeneous hypointense on the T1-weighted image (Fig.2) and displays heterogeneous hyperintense on the T2 Dixon (Fig. 3) image, with peripheral enhancement after contrast administration (Fig. 4). No septal enhancement is seen.
An additional computed tomography (CT) (Fig. 5, 6) was requested, showing a radial thick periosteal bone formation of the ilium which confirmed the chondroid matrix mineralization. These imaging findings were highly suggestive of a chondroid surface lesion of bone. A biopsy was done and the histopathology confirmed chondrocytes located in the background of hyaline cartilage compatible with the radiological diagnosis of periosteal chondrosarcoma.
Periosteal chondrosarcoma is a rare primary malignant bone tumour. According to the classification of the World Health Organization (WHO), it emerges from the periosteum of the bone and histological grading is not applicable. [1, 2]
As it arises from the external bone surface is also named juxtacortical chondrosarcoma and typically produces a cartilage matrix and is surrounded by a fibrous pseudocapsule that continues with the periosteum. [1, 3, 4, 5, 6]
Characteristically affects the metaphyseal zone of long bones, especially the posterior aspect of the distal femur, however, any bone can be affected and a few unusual cases were reported at the ilium. [5]
Presents commonly in adults between the 3rd and 4th decade of life with a slight male predilection and clinical symptoms are nonspecific, including swelling, painless or painful mass. [2, 3, 5, 6]
Due to the nonspecific presentation, radiological findings represent a crucial role to differentiate periosteal chondrosarcoma from other surface tumours as the correct treatment with wide surgical resection provides an excellent prognosis. [3, 4]
As MRI is having a higher performance into evaluate bone marrow and soft tissues it is superior to all the other imaging methods to characterize the tumour. [2, 6]
The lesion normally presents on MRI as a soft tissue mass ascending from the surface of the bone with an intermediate to low intensity on T1-weighted sequences and a lobulated high-signal on T2-weighted sequences. Peripheral and septal enhancement occurs after intravenous contrast administration. [2, 7]
CT is ideal to identify calcifications that characterize the cartilage matrix and to evaluate cortical changes and periosteal reaction. [2, 3, 5, 6]
Periosteal chondrosarcomas are identical histologically and radiologically to other surface tumours and periosteal chondroma may be the most difficult to distinguish as both tumours contain cartilage. Therefore, certain imaging features as the size of the lesion and cortical invasion are essential for differential diagnosis.[3, 4, 5, 6]
Considering that periosteal and parosteal osteosarcomas histologically also demonstrate chondroid matrix mineralization must be included in the differential diagnosis, although those lesions present osteoid matrix and bone tumoral formation.[4, 5]
In conclusion, periosteal chondrosarcoma is a rare primary low-grade surface bone tumour and the iliac bone is an uncommon location. Radiologists must be aware of the imaging aspects and differential diagnosis which is crucial for clinical management and prognosis depending on de appropriate surgical excision.[4]
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Periosteal chondrosarcoma
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This patient underwent a pelvis anteroposterior (AP) X-ray, CT, and MRI examination. A soft tissue mass-like lesion was found on the lateral cortical surface of the right iliac bone, showing relatively well-defined and exophytic growth. The imaging characteristics in each sequence are as follows:
Given the age of 37, the clinical presentation (persistent lower back pain radiating to the right lower extremity for several months), and the imaging characteristics of cartilaginous matrix calcification, the following conditions can be considered:
Taking into account the patient's age, symptoms, and the imaging findings mentioned above, the most likely diagnosis is: Periosteal Chondrosarcoma. For further confirmation, pathological biopsy can be performed to determine the tumor’s nature and grade.
Disclaimer: This report is a reference analysis based on imaging and clinical information and cannot replace in-person consultation or professional medical advice. If you have any concerns or if symptoms worsen, please visit a hospital promptly.
Periosteal chondrosarcoma
