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
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.
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.