They show a clear picture of dense structures of bones, and will also indicate bone growth pertaining to osteochondroma. Computed tomography (CT) scan can identify the bony lesion in great details and show the presence of calcification. These tests also provide great details, especially in soft tissues with the aide of cross-sectional images. Magnetic resonance imaging (MRI) is the most accurate method for detecting bone masses in symptomatic cases to depict precise morphology of a tumor. It is used to verify if the palpable mass is continuous with the cortex of the affected bone and to differentiate an osteochondroma from other lesions on the surface of the bone. MRI can also be used to look for cartilage on the surface of tumor and can depict any vascular complications caused by the tumor. An MRI can identify tumors of the spinal column and is often used to diagnose low grade osteosarcoma. Ultrasound is done if aneurysms or pseudoaneurysms and venous or arterial thrombosis is suspected. Ultrasound is an accurate method for examining the cartilaginous cap of the osteochondroma. It is also a way of pinpointing bursitis. However, it cannot be used to predict if the growth of tumor is inward in regards to the cap. Angiography is used to detect vascular lesions caused by osteochondroma due to ossified cartilaginous cap. It is also used to characterize malignant transformation lesions through neovascularity. Clinical testing such as sequence analysis can be done of the entire coding regions of both EXT1 and EXT2 to detect mutations.
The results of immunohistochemistry and multiple sequence alignment supports the cause of MO being a mutation in EXT1 gene. However, the exact molecular mechanism of multiple osteochondroma remains unclear. The EXT1 gene encodes the endoplasmic reticulum-resident type II transmembrane glycosyltransferase, which catalyzes polymerization of heparin sulfate chain at the endoplasmic reticulum and the Golgi apparatus. Heparin sulfate regulates signal transduction during chondrocyte differentiation, ossification, and apoptosis. Malfunction in heparin sulfate synthesis causes chondrocytes to rapidly differentiate. Based on these results future studies should elucidate the underlying molecular mechanism of the glycosyltransferase domain of the EXT1 and its involvement in the development of multiple osteochondromas. Osteochondromas are associated with secondary peripheral chondrosarcomas, but the pathogenesis of the malignant bone tumor remains unknown. Research has demonstrated that chondrocytes with dysfunctional EXT1 is present in solitary osteochondromas, but the EXT1 is functional in sporadic (solitary) secondary peripheral chondrosarcomas. Research indicates that osteochondromas creates a special niche in which wild type cells are mixed in with EXT functional cells. Then these EXT functional cells undergo other mutations, that give rise to secondary peripheral chondrosarcoma, indicating the involvement of an alternative mechanism for the pathogenesis of secondary peripheral chondrosarcoma. Future studies should address the contributing gene that causes the formation of peripheral chondrosarcoma. It should also illustrate what causes chondrocytes functional with EXT1 and EXT2 within the osteochondroma to become more susceptible to mutations leading to malignancy. References
External links
Humpath #2790 (Pathology images)
American Academy of Orthopedic Surgeons