The specimen shows the effects of a tumour called a chondrosarcoma on the bones of the left side of the pelvis (the right side in the picture). The left ilium, the large curved bone which along with the right ilium comprise the major part of the pelvis, is highly degraded and damaged towards the front, to the point of having considerable bone loss. The socket for the head of the femur, situated in the lower portion of the ilium, has virtually disintegrated. This makes a precarious, almost non-existent seating for the head of the femur, the relatively normal looking round bone on the right. The pubic bone, which forms the front part of the pelvis, has largely disintegrated on the right side of the picture. The right pelvis and its bones (on the left side of the picture) look normal.
Chondrosarcomas are a member of a class of tumours of bone and soft tissue called sarcomas. Chondrosarcoma occurs when the cells that make cartilage undergo cancerous change, growing uncontrollably and destroying the surrounding bone. In a normal skeleton there is a process of bone renewal going on throughout life, and osteoclasts are the cells responsible for the dissolving of old bone so that it can be replaced with new bone. However, as the chondrosarcoma grows, osteoclasts accumulate in abnormally high numbers in and around the tumour, dissolving bone and causing the excessive bone loss seen in the specimen. This allows the chondrosarcoma cell to grow and produce large abnormal lakes of cartilage, as shown in the large pale area in the middle of the microscopic section of a chondrosarcoma shown below.
The cancer cells can break away from the primary chondrosarcoma and travel to other bones, the lungs or other organs, where they can grow into secondary tumours. Chondrosarcoma typically affects adults between the ages of 20 and 60 years, and is more common in men than in women. As in this specimen, the pelvis is a common site where it arises.