CASE 149

By: Dr. Nizar Al-Nakshabandi MD, FRCPC

HISTORY:  75-year-old male with right arm pain following trivial trauma. On examination there is a lump in the right upper arm.

FINDINGS:

X-ray [A] demonstrates lytic lesion in the proximal metadiaphysis of the right humerus with a chondroid matrix and endosteal scalloping. There is evidence of a pathological fracture that is oriented obliquely.

Transaxial computed tomography [B] bone window confirms the lytic lesion with a chondroid matrix manifested by rings and arcs or popcorn appearance for. Fracture is confirmed and there is evidence of a soft tissue component extending both medially and laterally in the soft tissues.

Transaxial computed tomography [C] lung window, demonstrates a metastatic nodule to the right upper lung lobe.

Coronal reformat CT [D] of the right humerus demonstrates the extent of soft tissue involvement, and absence of joint or lymph node involvement.

DIFFERENTIAL DIAGNOSIS:

Since this is an aggressive bony lesion, the differential diagnosis should include primary conventional intramedullary chondrosarcoma, osteomyelitis would seem less likely because of the chondroid matrix. Secondary chondrosarcoma from pre-existing cartilaginous lesions should be considered as well.

DIAGNOSIS:

Chondrosarcoma.

PEARLS AND DISCUSSION:

Chondrosarcoma is a malignant chondroid tumor typically in the elderly and typically after the fifth decade of life with slight male predominance. On imaging, these lesions have ring and arc or popcorn appearance as well as Endosteal scalloping or pathological fracture. Soft tissue mass component can be seen with them.

These lesions can be primary de novo and, in that case, that would include conventional intramedullary chondrosarcoma, juxtacortical chondrosarcoma, clear cell chondrosarcoma, or myxoid chondrosarcoma. Alternatively, they can be secondary to a pre-existing cartilaginous tumor such as a osteochondroma or enchondroma.

These tumors love long bones and therefore are seen most likely in the femurs, tibia, or humerus as in our case. However, they have been reported in the pelvis, ribs and spine but rarely in the hands and feet where enchondroma is the cause.

The full staging of these cases, following a plain radiograph is by CT or MRI in the cases CT, was suffice as it demonstrated the pathological fracture, and the popcorn calcification as well as no joint involvement or lymph node involvement. Nuclear medicine can be performed to rule out multiplicity of lesions. CT scan of the chest should be done to exclude lung metastasis. In our case the CT proved to be positive for lung metastasis.

Sarcomas in general have a-high affinity to go to the lungs.

FURTHER READING:

1.      Murphey MD, Walker EA, Wilson AJ et-al. From the archives of the AFIP: imaging of primary chondrosarcoma: radiologic-pathologic correlation. Radiographics. 23 (5): 1245-78.

2.      Geirnaerdt MJ, Hogendoorn PC, Bloem JL et-al. Cartilaginous tumors: fast contrast-enhanced MR imaging. Radiology. 2000;214 (2): 539-46

3.      Varma DG, Ayala AG, Carrasco CH et-al. Chondrosarcoma: MR imaging with pathologic correlation. Radiographics. 1992;12 (4): 687-704