Heterogeneity in growth properties of the rat Swarm chondrosarcoma.

Chondrosarcoma remains one of the most difficult clinical conundrums of orthopaedic pathology, with wide variation in clinical course. The natural history of chondrosarcoma ranges from slow indolent growth without metastasis over years to rapid proliferation and lethal metastasis. Molecular regulatory events in the growth of these neoplasms are poorly understood. Of the Swarm rat chondrosarcoma, originating from a single neoplasm in a Sprague-Dawley rat more than thirty-five years ago, two populations were identified with different growth properties. These two Swarm chondrosarcoma lines were characterized for growth properties, histomorphometric and ultrastructural integrity, and the ability for proteoglycans to form aggregates with hyaluronan. After careful comparison, no obvious clues to the variation in growth rate were noted. Further molecular analyses may lead to better understanding of the differential growth properties of these cell lines. Understanding the mechanisms involved in differential growth rates may lead to clinically applicable clues to predict clinical behavior of chondrosarcomas in humans.