Contributed by: Ed Boas

20 year old otherwise healthy woman presented with a palpable bump in the region of her left 12th rib, with minimal pain.  CT showed a 10 cm calcified mass arising from the left 12th rib, involving the diaphragm, and displacing the kidney and spleen.  Differential diagnosis included chondrosarcoma and osteosarcoma.  The patient was seen at tumor board, where an incisional biopsy was recommended, as osteosarcoma would be treated with pre-operative chemotherapy, and chondrosarcoma would proceed immediately to resection.  Biopsy showed low grade chondrosarcoma.  The mass was resected along with a portion of the diaphragm, which was reconstructed using a Gore-Tex patch.  Pathology showed low grade chondrosarcoma.
The radiographic appearance of chondrosarcoma reflects the popcorn-like "ring-and-arc" ossification in a chondroid matrix.  The chondroid matrix has a high water content, and is therefore low attenuation on CT (hypodense to muscle), and T2 bright on MRI.  Contrast-enhanced MRI shows a ring-and-arc pattern of enhancement.  There can also be endosteal scalloping or cortical destruction with soft tissue extension.  The most common locations are the pelvis, ribs, femur, and humerus.
Differential diagnosis includes enchondroma and osteosarcoma.  Enchondromas typically do not cause pain, or have cortical destruction.  Osteosarcoma does not have chondroid matrix, and typically occurs in younger patients.

Gross features: Cartilage with focal areas of ossification.  Focal areas of cortical destruction and soft tissue extension can be seen.
Histology: Irregular lobules of hyaline cartilage containing clusters of chondrocytes.  There is associated ring-and-arc calcification, and destruction of surrounding trabecular bone.

Surgical excision.  Biopsies must be planned with future tumor excision in mind.
5-year survival is 90% for grade 1, 81% for grade 2, and 29% for grade 3 chondrosarcoma.
Murphey MD, Walker EA, Wilson AJ et al.  (2003)  Imaging of primary chondrosarcoma: Radiologic-pathologic correlation.  RadioGraphics.  23: 1245-78.
Marco RAW, Steven G, et al.  (2000)  Cartilage tumors: Evaluation and treatment.  J Am Acad Orthop Surg 8: 292-304.
Gelderblom H, Hogendoorn PCW, Dijkstra SD, et al.  (2008)  The clinical approach towards chondrosarcoma.  The Oncologist.  13: 320-9.

Accession: CL0122

Study description: