Abstract
Aim
Multiple (hereditary) osteochondroma (MO) is a rare autosomal dominant disease. Previous reports show that the risk of a malignant degeneration varies between 5-25%, but these are often combined with data on other cartilaginous diseases. The aim of this study was to establish clinical and radiological parameters that could identify a group of MO patients who are at risk for peripheral chondrosarcoma.
Methods
A database of 64 MO patients surgically treated between 1980-2009 was established. For 24 patients full radiological (including MRI), surgical and pathological records were complete. This group contained 14 osteochondroma patients and 10 chondrosarcoma patients. Non-parametric tests and Kaplan-Meier survival analysis were used to establish a cartilage-cap thickness cut off point and a volume cut off point.
Results
A total of 450 osteochondromas were seen in 64 patients, most common sites were the distal femur (14%) and the proximal tibia (12%). Eighteen patients developed a chondrosarcoma (28%), the most common sites were the ribs (22%) and the proximal femur (17%). Between osteochondromas and chondrosarcomas there was no significant difference in clinical symptoms like pain (10% vs 29% p=0,472) and growth (25% vs 30% p=0,669). The median cartilage-cap thickness was 5mm (range 1-12) for benign and the median cartilage-cap thickness was 40mm (range 15-130) malignant lesions, with a cut-off point at 8mm. Chondrosarcomas had a larger median volume of 227cm3 (range 2-147) compared to 51cm3 (range 37-545) in the osteochondroma group, with a cut-off point at 175cm3.
Conclusion
Clinical symptoms (pain and growth) are non-reliable indicators for malignancy. In MO patients a cartilage-cap thickness larger than 8mm or a tumour-volume larger than 175cm3 should be considered malignant. Lower thickness of the cartilage cap than earlier reported and volume measurement both based on MRI, are indicators for malignant degeneration and should be implemented in screening protocols.
