Answer for BIR CoW 24 Dec 2023
Osteochondroma with malignant tranformation
Findings
Relatively well defined T2 heterointense lesion noted arising from medial tibial condyle extending to involve posteromedial aspect of left knee joint The lesion measures 7.4 x 13 x 20 cm The lesion shows diffusion restriction with multiple areas of blooming foci T2/STIR hyperintensity noted in proximal tibia - F/S/O Osteochondroma with malignant transformation
Discussion
Cartilage-capped osseous excrescence with continuous cortex and marrow extending from underlying bone Clinical presentation • Knobby mass, long duration • Mechanical pain from trauma or impingement • Limited range of motion and snapping tendons from impingement • Nerve impingement • Rapid painful "enlargement" from overlying bursa Location Metaphysis/metaphyseal equivalents (rarely diaphysis) 95% located in extremities Femur (30%) > tibia (20%) > humerus (10-20%) Lower extremity > upper extremity (2:1) 40% around knee Radiographic Findings Composed of stalk, marrow, and cortex; all continuous with normal underlying bone If near joint, tends to project away from joint line, growing along forces generated by location of tendons and ligaments Lesions arising in pelvis may become very large before discovery Lesions in ribs most often arise from costochondral junction; may give appearance of pulmonary nodule Lesion may be sessile (broad-based), mimicking undertubulation of metaphysis Endochondral calcification may be seen within cartilage cap and medullary bone – Rings and arcs, punctate, or flocculent calcification CT Mimics those of radiograph; may show relationship of lesion to cortex and marrow better Cartilage cap thickness may be evaluated if mineralized or if overlying soft tissues are thin; otherwise may be difficult MRI Normal bone marrow extending into exostoses Cortex continuous with that of underlying bone Hyaline cartilage cap, mildly undulating and not exceeding 1 cm width Cap has lobulated high signal of hyaline cartilage on fluid-sensitive sequences Cap covered by thin perichondrium, low signal on T1 and T2 sequences In young patients with active growth, cartilage has different normal appearance – May be up to 3 cm thick – Shows marked heterogeneity on all sequences Mineralized areas within cap and exostosis remain low signal on all sequences Enhancement limited to thin fibrovascular tissue covering cartilage cap and thin septa within cap Bursal lining may develop metaplasia → synovial chondromatosis
References
Wolfgang Dähnert. Radiology Review Manual. (2007) ISBN: 9780781766203 Ronald L. Eisenberg, Nancy M. Johnson. Comprehensive Radiographic Pathology. (2007) ISBN: 9780323036245
Findings
Relatively well defined T2 heterointense lesion noted arising from medial tibial condyle extending to involve posteromedial aspect of left knee joint The lesion measures 7.4 x 13 x 20 cm The lesion shows diffusion restriction with multiple areas of blooming foci T2/STIR hyperintensity noted in proximal tibia - F/S/O Osteochondroma with malignant transformation
Discussion
Cartilage-capped osseous excrescence with continuous cortex and marrow extending from underlying bone Clinical presentation • Knobby mass, long duration • Mechanical pain from trauma or impingement • Limited range of motion and snapping tendons from impingement • Nerve impingement • Rapid painful "enlargement" from overlying bursa Location Metaphysis/metaphyseal equivalents (rarely diaphysis) 95% located in extremities Femur (30%) > tibia (20%) > humerus (10-20%) Lower extremity > upper extremity (2:1) 40% around knee Radiographic Findings Composed of stalk, marrow, and cortex; all continuous with normal underlying bone If near joint, tends to project away from joint line, growing along forces generated by location of tendons and ligaments Lesions arising in pelvis may become very large before discovery Lesions in ribs most often arise from costochondral junction; may give appearance of pulmonary nodule Lesion may be sessile (broad-based), mimicking undertubulation of metaphysis Endochondral calcification may be seen within cartilage cap and medullary bone – Rings and arcs, punctate, or flocculent calcification CT Mimics those of radiograph; may show relationship of lesion to cortex and marrow better Cartilage cap thickness may be evaluated if mineralized or if overlying soft tissues are thin; otherwise may be difficult MRI Normal bone marrow extending into exostoses Cortex continuous with that of underlying bone Hyaline cartilage cap, mildly undulating and not exceeding 1 cm width Cap has lobulated high signal of hyaline cartilage on fluid-sensitive sequences Cap covered by thin perichondrium, low signal on T1 and T2 sequences In young patients with active growth, cartilage has different normal appearance – May be up to 3 cm thick – Shows marked heterogeneity on all sequences Mineralized areas within cap and exostosis remain low signal on all sequences Enhancement limited to thin fibrovascular tissue covering cartilage cap and thin septa within cap Bursal lining may develop metaplasia → synovial chondromatosis
References
Wolfgang Dähnert. Radiology Review Manual. (2007) ISBN: 9780781766203 Ronald L. Eisenberg, Nancy M. Johnson. Comprehensive Radiographic Pathology. (2007) ISBN: 9780323036245
Note:
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!
We do not discourage differential diagnosis. But all the differentials must satisfy the findings noted in the case.
If you feel you have answered rightly but cannot find your name in the above list, please call 09551942599.
Did you Know?
The order in which the names appear in this winner's list is based on the time of submission. The first person to send the correct answer gets his/her name on top of the list!