Dedifferentiation is the process in which cells that have previously developed to more specialized cells return to their original state. If a tumor is labeled as “dedifferentiated,” that means immature cells were found in the biopsy sample when viewed under the microscope. Dedifferentiation can occur with chondrosarcomas, parosteal osteosarcomas and liposarcomas most commonly. In this situation, cells change and become more aggressive. A second type of more aggressive and higher grade, rapidly growing sarcoma develops from the low grade, slow growing chondrosarcoma, liposarcoma or parosteal osteosarcoma. This makes the tumor much more aggressive and the prognosis is poor. There is a high rate of cancer spreading.