This condition is characterised by the formation of multiple cartilaginous nodules in the synovium of joints, tendons and bursae.
The condition is always monoarticular. The knee (70%) and hip (20%) are the most commonly affected sites. The male to female ratio is 2:1. The age range is from 17 to 64 years
The cartilage is cellular, to a degree indistinguishable from low grade chondrosarcoma. Moderate to severe pleomorphism is seen in nearly 50% of cases. Binucleate cells are always present, but mitoses are not seen in benign lesions. 60% of cases show calcification, which is diffuse and punctate. Nearly 60% of cases show ossification, rarely marked. Joint space obliteration and extracapsular soft tissue masses are not, by themselves, indicative of malignancy.
The suggested criteria for malignancy are: (i) the presence of atypical chondrocytes in sheets diffusely scattered in the ground substance rather than arranged in nests, (ii) the presence of mitoses, (iii) crowding and spindling of nuclei at the periphery of lobules, (iv) necrosis, myxoid change and permeation of bone trabeculae.
The condition is usually benign, but may recur due to incomplete removal.
Advances in Anat Pathol 1999;6:61